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High Genetic Variance in Life-History Strategies within Invasive Populations by Way of Multiple Introductions
Abstract
Biological invasions represent major threats to biodiversity as well as large-scale evolutionary experiments. Invasive populations have provided some of the best known examples of contemporary evolution [3-6], challenging the classical view that invasive species are genetically depauperate because of founder effects. Yet the origin of trait genetic variance in invasive populations largely remains a mystery, precluding a clear understanding of how evolution proceeds. In particular, despite the emerging molecular evidence that multiple introductions commonly occur in the same place, their contribution to the evolutionary potential of invasives remains unclear. Here, by using a long-term field survey, mtDNA sequences, and a large-scale quantitative genetic experiment on freshwater snails, we document how a spectacular adaptive potential for key ecological traits can be accumulated in invasive populations. We provide the first direct evidence that multiple introductions are primarily responsible for such an accumulation and that sexual reproduction amplifies this effect by generating novel trait combinations. Thus bioinvasions, destructive as they may be, are not synonyms of genetic uniformity and can be hotspots of evolutionary novelty.
... In particular, two snail species of the family Thiaridae (Melanoides tuberculata and Tarebia granifera) have been extremely efficient IAS. Introduced in the late 1970s and early 1990s, respectively, as a consequence of aquarium trade, these two species now occupy most of Martinique hydrographic network, competing against each other and with local species (Delannoye et al., 2015;Dubart et al., 2019;Facon et al., 2008), and making up most of the benthic animal biomass in Martinican rivers (Dubart, 2019;Facon et al., 2008;Facon & David, 2006). ...
... In particular, two snail species of the family Thiaridae (Melanoides tuberculata and Tarebia granifera) have been extremely efficient IAS. Introduced in the late 1970s and early 1990s, respectively, as a consequence of aquarium trade, these two species now occupy most of Martinique hydrographic network, competing against each other and with local species (Delannoye et al., 2015;Dubart et al., 2019;Facon et al., 2008), and making up most of the benthic animal biomass in Martinican rivers (Dubart, 2019;Facon et al., 2008;Facon & David, 2006). ...
... We considered here three mollusks species, T. granifera, M. tuberculata, and N. punctulata ( Figure 1). The first two species belong to the Thiaridae family and were introduced in Martinique in the late 1970s and early 1990s, respectively (Delannoye et al., 2015;Facon et al., 2008;Pointier et al., 1998). They represent by far the dominant component of mollusks in Martinique freshwaters, both occurring in the majority of watersheds -their densities vary in time, but can reach 10,000 ind./ m 2 in both species (Facon et al., 2008;Samadi et al., 1997;P. ...
The pace of biological invasions has increased in recent decades, leading to multiple invasions and the potential dominance of invasive species, destabilizing local ecological networks. This provides opportunities to study new ecological species interactions , including predation. Tropical freshwaters have been particularly concerned by aquatic invasions and we focused here on the Martinique island (Lesser Antilles). We examined the predator-prey relationships involving invasive Thiarid snails (Tarebia granifera and Melanoides tuberculata) and the native Neritina punctulata, both confronted with a newcomer predator, the redclaw crayfish (Cherax quadricarinatus). We conducted several mesocosm experiments to assess the impact of crayfish predation on snail survival and the passive and active antipredator responses of snails. A first experiment indicated snail survival rates between 50% and 80%, depending on crayfish size and sex. Notably, there was a negative correlation between snail survival and male crayfish size and the predation method (shell crushing vs. "body sucking") varied with crayfish size. The second experiment suggested no refuge size for snails, with both very small (<5 mm) and very large (>5 mm) unable to escape predation, regardless of crayfish size (from 77 to 138 mm) or sex. Finally, we investigated the escape behavior of Thiarids regarding three crayfish cues. Melanoides tuberculata tend to bury in the substrate and T. granifera to climb up aquarium walls, what was expected from their shell morphologies, and both responding to crayfish cues within minutes. Overall, C. quadricarinatus proves to be an efficient snail predator with limited escape options for snails, potentially contributing to the decline of certain snail populations in Martinique. This omnivorous predator might impact other native species across different groups, including shrimps and fish. Our study underscores the urgent need for monitoring efforts, solidifying the redclaw crayfish reputation as a dangerous invasive species for freshwater macrobenthic faunas worldwide. K E Y W O R D S chemical stimuli, escape behavior, mollusks, prey-predator interactions, refuge size, survival
... It is possible that some introduced populations of axis deer benefited from genetic admixture (Dlugosch et al. 2015;Colautti et al. 2017). The introduction of multiple genetic lineages could result in mixing of genetic material that normally would not occur in the native population due to geographic isolation, which then creates an admixture of genetic material previously limited to geographically disjunct lineages, potentially resulting in increased adaptive potential to new environments (Facon et al. 2008;Dlugosch et al. 2015;Colautti et al. 2017). In the case of axis deer in Texas and Hawaii, the single lineages that appear to have comprised the founding individuals of those populations likely did not allow for significant admixture to have occurred within these populations. ...
... However, despite the presence of just one mtDNA lineage in Texas, the widespread human-mediated movement of axis deer in Texas could facilitate gene flow, potentially reestablishing locally lost alleles. Conversely, in axis deer in Australia and Croatia, the presence of two founding lineages may have facilitated admixture between the two lineages (Facon et al. 2008;García et al. 2017;Hill et al. 2019;Šprem et al. 2021). The theoretical potential for genetic admixture between axis deer lineages may be demonstrated by examining the observed diversity between the Texas and Hawaii populations. ...
... 1), and could be valuable for identifying other potentially invasive lineages of axis deer. Such data from South America may be particularly important as there were multiple introductions to that continent, which may have provided a scenario for admixture there not observed elsewhere (Facon et al. 2008;Dlugosch et al. 2015;Colautti et al. 2017). ...
Human-mediated introductions and subsequent establishment and spread of nonnative species have the potential to create a founder effect in such populations, which typically results in low genetic diversity and potential for inbreeding. However, several exotic invasive species exhibit a “genetic paradox” in which they thrive and adapt to novel environments while also avoiding complications from low genetic diversity. Axis deer (Axis axis) were introduced into Texas, Hawaii, South America, Australia, and Croatia during the 19th and 20th centuries and successfully established large populations from a few founding individuals. Mitochondrial (Cytochrome-b, Cytb; displacement loop, D-loop) and nuclear (10 microsatellites) markers were used to assess genetic diversity within and between axis deer populations in Texas and Hawaii and then compared to other introduced (Australia and Croatia) and native (India) populations. Overall, mtDNA divergence was 0.54% (Cytb) and 1.55% (D-loop) indicating high mitochondrial similarity within the species. Further, each invasive population was composed of only one or two mtDNA haplotypes. Microsatellite allele diversity also was low within and between populations in Texas and Hawaii resulting in monomorphic loci and Hardy–Weinberg equilibrium violations in both populations. The low genetic diversity in native Indian axis deer and within and between invasive populations suggests that the introduced populations experienced founder effects following introduction, and yet overcame this potential handicap by undergoing successful establishment and expansion. Axis deer appear to be another successful invasive species characterized by the genetic paradox where they exhibit genetic profiles that suggest inbreeding effects should be imminent, yet display no signs of inbreeding and are highly successful adapting to novel environments.
... Genetic admixture is the result of when multiple introductions of a species are conducted to found new populations , Colautti et al. 2017). The introduction of multiple genetic lineages could result in the mixing of genetic material that normally would not occur in the native population due to geographic isolation creating a 'hybrid' of the genetics previously limited to the separate lineages (Facon et al. 2008, Colautti et al. 2017. This mixing may result in increased adaptive potential that may further enable the introduced population to adapt to their new environment (Facon et al. 2008, Colautti et al. 2017). ...
... The introduction of multiple genetic lineages could result in the mixing of genetic material that normally would not occur in the native population due to geographic isolation creating a 'hybrid' of the genetics previously limited to the separate lineages (Facon et al. 2008, Colautti et al. 2017. This mixing may result in increased adaptive potential that may further enable the introduced population to adapt to their new environment (Facon et al. 2008, Colautti et al. 2017). ...
... In the case of axis deer in Texas and Hawaii, the single lineages that appear to have comprised the founding individuals of those populations likely did not allow for significant admixture to have occurred. However, in the case of axis deer in Australia and Croatia, the presence of two founding lineages may have allowed admixture between the two lineages (Facon et al. 2008, García et al. 2017, Hill et al. 2019, Šprem et al. 2021). The potential for the mixing of nuclear genetic material between the genetic lineages present in Australia and Croatia could be estimated by looking at the results of the mtDNA and microsatellite analyses conducted for this study in Texas and Hawaii. ...
... However, a variety of apparently successful invasive species, have led to the formulation of the genetic paradox of invasions (12,15), which describes the successful establishment of NIS populations with low levels of genetic diversity (13). This hypothesis has recently been challenged (16,17), with several studies of invasive populations that do not show reduced genetic diversity compared to their source populations (16,(18)(19)(20). In contrast, recent whole-genome data analyses have documented a severe reduction of genetic diversity during successful freshwater invasions of marbled crayfish in Madagascar (21). ...
... The genetic paradox of invasions (15) describes the successful establishment of invasive populations with low levels of genetic diversity. However, the general applicability of the paradox itself has also been challenged (16,17), with several reports of invasive populations that do not show reduced genetic diversity as compared to their source populations (19) or even showing increased diversity due to admixture from diverse source regions (18). Importantly, the mechanisms by which low genetic diversity due to founder effects in the invasive range can be circumvented are highly controversial (16,20). ...
... Importantly, the mechanisms by which low genetic diversity due to founder effects in the invasive range can be circumvented are highly controversial (16,20). The lack of evidence for strong founder events accompanying marine invasions is possibly driven by high propagule loads (20), multiple introductions (16), admixture from distant source populations (18) or a combination thereof. Furthermore, recurrent introductions can introduce additional genetic diversity over time. ...
Significance
A central goal in invasion genomics is to identify and determine the mechanisms that underlie the successful colonization, establishment, and subsequent range expansion of invasive populations of nonindigenous species. Using a whole-genome approach, we evaluate the importance of genetic diversity for the successful establishment of nonindigenous species. Our study shows that genetic diversity per se is not the major factor driving invasions, since we observed all possible scenarios with invasive populations showing reduced, similar but also increased, genetic diversity relative to the native population. Using coalescent methods, we reconstruct the demographic history of the invasion and infer the source population of each invasion event, which shows that propagule pressure and multiple introductions play an important role in determining invasion success.
... The high invasiveness of R. nomadica, the size of its summer and winter swarms (Spanier and Galil 1991;Deval and Olguner 2019;Edelist et al. 2020) and its integration with native fauna (Zeidler et al. 2018), reveal the needs for deeper understanding of R. nomadica population genetics patterns and characteristics. Whereas introduced populations commonly experience a loss of genetic diversity relative to the native populations due to founder effects and postintroduction demographic bottleneck (Phillips and Shine 2005;Darling et al. 2008;Facon et al. 2008;Bai et al. 2012), successful invasive species can overcome depletion of genetic diversity by fast development of putative adaptive traits, while others exhibit phenotypes with a broad tolerance to environmental drivers (Dlugosch and Parker 2008). The literature supplies examples for invasive populations that did not show the expected reduction in genetic diversity, and in cases of multiple independent introductions, even higher diversity may prevail (Darling et al. 2008;Dlugosch and Parker 2008). ...
... Further, COI sequences confirmed classical taxonomy, assigning R. nomadica as a separate valid species. In contrast to the common viewpoint that, compared to source populations, invasive species may be subject to high founder's effects and genetic bottleneck risks (Phillips and Shine 2005;Darling et al. 2008;Facon et al. 2008;Bai et al. 2012), we present in the Levantine R. nomadica population an extensive repertoire of COI haplotypes, with a large number of singletons (51.68%). This outcome mirrors documentation of invasive populations similarly characterised by large numbers of COI haplotypes and singletons (Table 6 provides 10 cases for populations of invasive species, each with 19-95 COI haplotypes and 49.4-82.6% of singletons). ...
... This outcome mirrors documentation of invasive populations similarly characterised by large numbers of COI haplotypes and singletons (Table 6 provides 10 cases for populations of invasive species, each with 19-95 COI haplotypes and 49.4-82.6% of singletons). The above results have been attributed to multiple and independent introductions, or to the establishment of an open corridor, leading to ''propagule pressure'' and augmented gene flow (Trontelj et al. 2005;Golani et al. 2007;Roman and Darling 2007;Darling et al. 2008;Facon et al. 2008). The scenario of multiple independent introductions throughout the Suez Canal corridor (sensu Galil 2006) seems suitable to the Levantine R. nomadica population, characterized with high number of COI haplotypes and with increased numbers of singletons. ...
Large blooms of Rhopilema nomadica, a highly venomous rhizostamatid scyphozoan species introduced to the Mediterranean through the Suez Canal, have become ubiquitous in the summer and winter months along the Israeli coasts since the mid-1980s. This species has since spread across the eastern Mediterranean and was sighted as far west as Tunisia and Sardinia. For the past 12 years, we have studied changes in the mitochondrial COI haplotypes diversity of R. nomadica to investigate small scale fluctuactions of genetic diversity and to reveal possible genetic structuring of the fast spreading invader in the Eastern Mediterranean. The 1091 COI sequences analysed, revealed a highly diverse population displaying 89 haplotypes, 46 of which appeared as singletons, low frequency haplotypes. All the specimens analysed throughout the period belong to a single unstructured population. Though lacking data from the source population in the Red Sea, the high within-population diversity and the high diversity of COI haplotypes support the hypothesis of multiple introductions events, or an open corridor with a continuous influx of propagules. Tajima’s D and Fu’s Fst negative values and the increased numbers of COI singletons from early to late sampling periods, have verified that the Israeli population is characterized by a rapid expanding population. Further research is needed for the evaluation of COI diversity and patterns in R. nomadica populations across the eastern Mediterranean Sea and Red Sea, as well as any correlation of the high variability between COI locus and phenotypic diversity.
... Our study found high microsatellite diversity compared to other U.S. populations of apple snails (Underwood et al. 2019) and detected moderate losses compared to native populations (Matsukura et al. 2016). While unexpected in this case, it is not uncommon for invasive populations to demonstrate high genetic diversity (Roman and Darling 2007;Facon et al. 2008). High diversity in invasive populations is most often associated with multiple introductions (Kolbe et al. 2004;Dlugosch and Parker 2008). ...
... High diversity in invasive populations is most often associated with multiple introductions (Kolbe et al. 2004;Dlugosch and Parker 2008). The introduction of apple snails in Louisiana is most often attributed to an aquarium release around 2006 (Howells et al. 2006); however, aquarium releases only introduce a few propagules into the environment (Padilla and Williams 2004), so numerous release events from diverse sources would have been necessary to explain the observed high diversity (Facon et al. 2008). Other sources of diversity may include mutation or inoculation by females carrying sperm from multiple males (Eales et al. 2010). ...
Aquatic invasive species decrease biodiversity and disrupt economic systems worldwide. Apple snails (Ampullaridae) from the genus Pomacea are globally invasive species that are highly damaging to aquaculture and aquatic ecosystems. Pomacea maculata was introduced to Louisiana in the early 2000s and rapidly spread throughout the southern half of the state, where invasive populations now threaten valuable aquaculture economies and a large area of aquatic ecosystems that sustain biodiversity important to commercial and recreational fisheries. Despite these risks, little work has been dedicated to understanding how apple snails disperse through invaded areas in Louisiana. To shed light on potential dispersal dynamics, we assessed population genetic structure of P. maculata in Louisiana at multiple spatial scales using microsatellites of snails collected from seven sampling locations. Overall, genetic diversity was relatively high across all sampling locations. Significant genetic structure was observed among sampling sites, indicating Barataria Preserve and the four sampling locations within Terrebonne Basin as distinct populations. Genetic distances were smallest among the four sampling locations within Terrebonne Basin. These findings suggest that dispersal within hydrologic units is higher than between units, meaning that apple snails may primarily move through systems through passive downstream dispersal. However, geographically distant populations also showed evidence of genetic mixing, pointing toward human-aided long-distance dispersal events. Regular dispersal of apple snails within and among hydrologic units highlights the risk of invasions in highly interconnected aquatic systems where dispersal rates may be especially high due to human modifications.
... Since bottlenecks are common after laboratory colonization (Gloria-Soria et al. 2019), the bottlenecks detected in Spring Valley and Fire Island are likely the result of the colonization process. A growing number of studies have now demonstrated that the genetic diversity patterns following an invasion event are complex and depend on the size of the propagule (number of individuals invading), frequency of introductions, number of sources, admixture events, or a combination of these (Lockwood et al 2005;Dlugosch and Parker 2008;Facon et al. 2008;Handley et al. 2011;Bock et al. 2015;Jaspers et al. 2021). Different invasion scenarios may result in lower, equal, or higher genetic diversity metrics in the non-native range relative to the native range (Jaspers et al. 2021). ...
... High H o values at the invasive range of Ae. albopictus have also been reported by others using allozymes (Black et al. 1988), microsatellites (Manni et al. 2017), and genomewide single nucleotide polymorphisms [SNPs] (Kotsakiozi et al. 2017). The observed genetic diversity in the northeastern USA could be explained by expanding propagules that are subjected to drift and then merge (admixture), or by constant input of alleles that restore the original diversity levels and could possibly exceed them (Lockwood et al. 2005;Facon et al. 2008). In Ae. japonicus, another Asian container-breeding mosquito that invaded the USA, merging of two genetic groups was reported in Pennsylvania between 1999Pennsylvania between /2000Pennsylvania between and 2004Pennsylvania between /2005 and resulted in the loss of the original introduction bottleneck signature and high levels of genetic diversity (Fonseca et al. 2010). ...
The Asian tiger mosquito ( Aedes albopictus ) arrived in the USA in the 1980’s and rapidly spread throughout eastern USA within a decade. The predicted northern edge of its overwintering distribution on the East Coast of the USA roughly falls across New York, Connecticut, and Massachusetts, where the species has been recorded as early as 2000. It is unclear whether Ae. albopictus populations have become established and survive the cold winters in these areas or are recolonized every year. We genotyped and analyzed populations of Ae. albopictus from the northeast USA using 15 microsatellite markers and compared them with other populations across the country and to representatives of the major global genetic clades to investigate their connectivity and stability. Founder effects or bottlenecks were rare at the northern range of the Ae. albopictus distribution in the northeastern USA, with populations displaying high levels of genetic diversity and connectivity along the East Coast. There is no evidence of population turnover in Connecticut during the course of three consecutive years, with consistent genetic structure throughout this period. Overall, these results support the presence of established populations of Ae. albopictus in New York, Connecticut, and Massachusetts, successfully overwintering and migrating in large numbers. Given the stability and interconnectedness of these populations, Ae. albopictus has the potential to continue to proliferate and expand its range northward under mean warming conditions of climate change. Efforts to control Ae. albopictus in these areas should thus focus on vector suppression rather than eradication strategies, as local populations have become firmly established and are expected to reemerge every summer.
... Kemampuan distribusinya yang tinggi membuat M. tuberculata dikatagorikan sebagai spesies invasif dan menjadi ancaman bagi kestabilan ekosistem perairan tawar dan keragaman komunitas fauna asli (Samadi et al., 1999;Facon et al., 2008). Tingginya kemampuan invasi keong ini selain disebabkan oleh kisaran toleransinya yang luas terhadap faktor-faktor abiotik habitat, juga karena sifat partenogenesis-nya yang memungkinkan individu tunggal mampu membentuk koloni baru. ...
... Dechruksa et al. (2013) (Samadi et al., 1999). Banyaknya variasi-variasi morfologi pada suatu populasi lebih lanjut akan berpengaruh hingga ke tingkat molekuler (Facon et al., 2008). Variasi antar spesies dalam hal ini antara M. tuberculata dan S. punctata digunakan sebagai dasar dalam pemisahan penentuan identitasnya. ...
The freshwater Melanoides tuberculata (Thiarid) has wide distribution and have many variation in color, size, and scluptured of their shells. Comparing with another Thiarid so called Stenomelania punctata, shell of M. tuberculata similar in having turreted shape, blackish color, number of whorls, and size of the shells. This study aim to compare more detailed between M. tuberculata and S. punctata based on their morphology, ontogeny and type of reproduction. Ontogeny studies of these two species show that M. tuberculata produces juveniles in embryonic shell form during their reproduction. This embryonic shell is nourished and developed in the subhaemocoelic brood-pouch organ as evidenced by being found in the size range 0.12–5.95 mm. One individu M. tuberculata can produce 1–66 embryonic shells. Meanwhile, in subhaemocoelic brood-pouch of S. punctata only the unshell embryo was seen and embryonic shell was not found. The difference of reproduction system determines the reproductive strategy in both species. M. tuberculata conduct euviviparity reproduction whereas S. punctata is ovoviviparous that releases juveniles in free-swimming veliger form.
... Individuals of M. tuberculata are equipped to reproduce via parthenogenesis, which enables the facilitation and occupation of unfamiliar environmental localities in abundance (da Silva and Barros 2015). It has also been established that in rare events, M. tuberculata undergo sexual reproduction, enabling them to acquire genetic diversity amongst the population, which in turn affords them the ability to adapt morphologically and physiologically in order to survive in new environments and increase their global distribution and abundance (Facon et al. 2008). Once established in these new environments with new environmental characteristics that were once lethal to the organisms, M. tuberculata revert back to reproducing parthenogenetically in order to dominate the environment and outcompete any native species in the habitat, ultimately ensuring the survivability of the species (Facon et al. 2008;Farani et al. 2015). ...
... It has also been established that in rare events, M. tuberculata undergo sexual reproduction, enabling them to acquire genetic diversity amongst the population, which in turn affords them the ability to adapt morphologically and physiologically in order to survive in new environments and increase their global distribution and abundance (Facon et al. 2008). Once established in these new environments with new environmental characteristics that were once lethal to the organisms, M. tuberculata revert back to reproducing parthenogenetically in order to dominate the environment and outcompete any native species in the habitat, ultimately ensuring the survivability of the species (Facon et al. 2008;Farani et al. 2015). Other traits included a high rate of fecundity, protection from predators, because of their shell or utilising the sediment in which they bury themselves to their advantage (Hoy et al. 2012;Farani et al. 2015). ...
Anthropogenic activities have propelled the exploitation of natural environments, which along with climate change have resulted in salinity intrusion to freshwater ecosystems worldwide. To determine the extent the hypersalinity stressor has on freshwater ecosystems, physiological cardiac responses in the freshwater gastropod Melanoides tuberculata were analysed during an acute exposure to varying salinity concentrations. A non-invasive method was used to monitor the cardiac activity of the organisms. The mean heart rate (bpm) of M. tuberculata declined significantly between 20 ppt and 30 ppt. Melanoides tuberculata exhibited a hypersalinity threshold of 25 ppt and tolerated salinity concentrations up to 50 ppt. Data collected provide background data for the use of M. tuberculata as a bioindicator organism to assess the effects of hypersalinity on cardiac response of organisms in a freshwater ecosystem.
... For instance, the implications for management can be very different if the species spread from a single source population (i.e., one introduction event, high intrinsic capacity of expansion; for example, Cao et al., 2016;Trumbo et al., 2016;Zhang et al., 2019) or if the distribution in the non-native range is a consequence of multiple independent introduction events (i.e., this may suggest a more limited intrinsic capacity of expansion; for example, Hagenblad et al., 2015;Lejeusne et al., 2014;Miller et al., 2005;Xia et al., 2020). Determining the genetic background and origin of introduced populations is not only important to understand invasion routes and modes, but can also help to forecast admixture among previously isolated gene pools in the non-native range, and anticipate its potential negative impacts (Facon et al., 2008Kolbe et al., 2004). Interbreeding among introduced populations with different origins can quickly restore genetic diversity after strong founder effects, and increase the evolutionary potential of alien species through new allele combinations, which can ultimately boost their capacity to become invasive and outcompete native species with similar ecological requirements (Facon et al., 2008; but see Tsutsui et al., 2000). ...
... Determining the genetic background and origin of introduced populations is not only important to understand invasion routes and modes, but can also help to forecast admixture among previously isolated gene pools in the non-native range, and anticipate its potential negative impacts (Facon et al., 2008Kolbe et al., 2004). Interbreeding among introduced populations with different origins can quickly restore genetic diversity after strong founder effects, and increase the evolutionary potential of alien species through new allele combinations, which can ultimately boost their capacity to become invasive and outcompete native species with similar ecological requirements (Facon et al., 2008; but see Tsutsui et al., 2000). Genomic-based demographic reconstructions also have a high potential to understand the colonization history of invasive species, determine the mode of spread (e.g., gradual vs. explosive), and estimate the duration of lag phases between introduction and invasion if benchmark dates on the timing of introductions are available (Coutts et al., 2018;Kowarik, 1995;Puckett & Munshi-South, 2019;Rouget et al., 2016;Ryan et al., 2019). ...
The study of the genetic makeup and demographic fate of alien species is essential to understand their capacity to recover from founder effects, adapt to new environmental conditions and, ultimately, become invasive and potentially damaging. Here, we employ genomic data to gain insights into key demographic processes that might help to explain the extraordinarily successful invasion of the Western Mediterranean region by the North American boatman Trichocorixa verticalis (Hemiptera: Corixidae). Our analyses revealed the genetic distinctiveness of populations from the main areas comprising the invasive range and coalescent-based simulations supported that they originated from independent introductions events likely involving different source populations. Testing of alternative demographic models indicated that all populations experienced a strong bottleneck followed by a recent and instantaneous demographic expansion that restored a large portion (>30%) of their ancestral effective population sizes shortly after introductions took place (< 60 years ago). Considerable genetic admixture of some populations suggest that hypothetical barriers to dispersal (i.e., land and sea water) are permeable to gene flow and/or that they originated from introductions involving multiple lineages. This study demonstrates the repeated arrival of propagules with different origins and short time lags between arrival and establishment, emphasizing the extraordinary capacity of the species to recover from founder effects and genetically admix in invaded areas. This can explain the demonstrated capacity of this aquatic insect to spread and outcompete native species once it colonizes new suitable regions. Future genomic analyses of native range populations could help to infer the genetic makeup of introduced populations and track invasion routes.
... The levels of genetic polymorphism and differentiation in populations of non-indigenous species greatly affect their evolutionary changes (Barrett and Richardson 1986;Crawford and Whitney 2010;Lawson Handley et al. 2011;Bock et al. 2015). Recent studies suggest that among invasive molluscs there are examples of both populations with high genetic variation and populations with a 'founder effect' (Holland 2001;Chandler et al. 2008;Facon et al. 2008;Cahill and Viard 2014;Lounnas et al. 2018;Underwood and Darden 2019). There is no consensus on the effect of genetic polymorphism on the invasion success (Frankham 2005). ...
... Such examples are known for invasive molluscs. Better-studied examples of freshwater and marine molluscs include Perna perna (L.), Dreissena polymorpha (Pallas, 1771) and D. bugensis (Andrusov, 1897), Limnoperna fortunei (Dunker, 1857), Melanoides tuberculata (Müller, 1774)(Holland 2001;Stepien et al. 2002;Facon et al. 2008;Duarte et al. 2018). Interestingly, in such populations there is often not only high genetic, but also high phenotypic variation. ...
The Caucasian snail Harmozica ravergiensis Férussac, 1835 (Gastropoda, Stylommatophora, Hygromiidae) and the Crimean snail Brephulopsis cylindrica Menke, 1828 (Gastropoda, Stylommatophora, Enidae) have been spreading across the northern borders of their ranges in recent years. Here I present a study of the variability of ISSR loci in the populations of H. ravergiensis and B. cylindrica outside their natural range, in the south of the Central Russian Upland (Belgorod Region, Russia). A comparison is made with populations of these snail species in their native area (respectively, the Caucasus and Crimea). Genetic polymorphism is generally at the same level in alien and natural populations of the species. However, in some geographically isolated alien populations, the variability indices are lower than in the native area. The level of genetic differentiation between geographically distant populations indicates different sources of invasion. A high level of genetic differentiation was also detected between native populations. No isolation by distance was found for the Belgorod populations of H. ravergiensis (Mantel test, R 2 =0.065; P = 0.110). The exchange of migrants between these local populations is probably occurring anthropogenically. ARTICLE HISTORY
... It is a ubiquitous species that can tolerate a broad spectrum of environmental conditions and colonize disturbed habitats such as garden ponds, artificial lakes, and irrigation systems. Its reproductive strategy can produce new genotypes that may invigorate its invasive ability (Facon et al. 2008). In its introduced range, there are reports of M. tuberculata outcompeting native species, however, the consequences are not always negative often helping to reduce intermediate host populations. ...
Human land-use plays an important role in the distribution of aquatic invasive species. The establishment of these species may have an unpredictable impact on their new environment. We analyzed the establishment of M. tuberculata, an invasive species, and its effect on the mollusc community in Ouagadougou's reservoir No.3. Mollusc samples were collected using an Ekman grab through sampling points randomly distributed across the whole reservoir. Collected specimens were sorted, preserved in alcohol at the field site and transported to the laboratory for identification. Species diversity, abundance and distribution were analyzed. Among the five species encountered, M. tuberculata and L. varicus were identified for the first time in this reservoir. M. tuberculata had the highest relative abundance (60.83%) and the highest density. The evenness was less than 0.5 for 72.5% (i.e. 21) of sampling points, reflecting the relative dominance of a single species, M. tuberculata. In terms of spatial distribution, the most widespread species in the study reservoir was M. tuberculata, followed by C. aegyptiaca and B. unicolor. M. tuberculata distribution in the reservoir mostly overlaps that of B. unicolor (0.45). Renewed monitoring efforts are needed to better understand the evolution of mollusc species in freshwaters of Burkina Faso to understand species extinction risks as well as the potential use of mollusk diversity measures as water quality indicators.
... Purging of the genetic load is one possibility (Crnokrak and Barrett 2002). Recurrent introductions of different genotypes can also increase the genetic variance and adaptability (Facon et al. 2008). However, the same single genotype can repeatedly invade new regions, resulting in low genetic variability in those regions. ...
Lymnaeid snails are simultaneous hermaphrodites that have a worldwide distribution, inhabiting freshwater areas from almost all continents ranging from tropical to arctic regions and from sea level to very high altitudes. In this chapter, we review the reproductive anatomy, behavioral and physiological traits, and mating strategies associated with increased survival and invasiveness of lymnaeids across different ecosystems around the globe. We also discuss the biotic and abiotic factors that can affect mating systems in this family, and how they have expanded their geographical range by natural, as well as human-mediated ways, likely promoting the spread of infectious diseases. Finally, we discuss why we believe that lymnaeids are suitable model organisms for studying mechanisms and processes involved in the ecology and evolution of mating systems and biological invasions.
... 4). There is some empirical support for these general theoretical results from studies of invasion biology, such as the finding that rare sexual reproduction combined with clonal propagation proved to be the best strategy for invasiveness in a freshwater gastropod (Facon et al. 2008). Barfield et al. (2011) presented a general deterministic schema for analyzing evolution in stage-structured populations, assuming sexual reproduction. ...
Reproductive mode may strongly impact adaptation in spatially varying populations linked by dispersal, especially when sexual and clonal offspring differ in dispersal. We determined how spatial structure affects adaptation in populations with mixed clonal and sexual reproduction. In a source-sink quantitative genetic deterministic model (with stabilizing selection around different optima), greater clonal reproduction or parent-offspring association (a measure of the part of the parent's phenotype other than the additive genetic component inherited by clonal offspring) increased the selective difference (difference between phenotypic optima) allowing sink populations to adapt. Given dispersal differences between clonally and sexually produced juveniles, adaptation increased with an increasing fraction of clonal dispersers. When considering migrational meltdown, partially clonal reproduction reduced cases where dispersal caused habitat loss. Stochastic individual-based simulations support these results, although the effect of differential dispersal was reversed, with decreased clonal dispersal allowing greater adaptation. These results parallel earlier findings that for an instantaneous shift in phenotypic optimum, increasing clonality allowed population persistence for a greater shift; here, selective change is spatial rather than temporal. These results may help explain the success of many partially clonal organisms in invading new habitats, complementing traditional explanations based on avoiding Allee effects.
... Thus, the "genetic paradox of invasions," the success of invasive species despite their low genetic diversity (Allendorf and Lundquist 2003;Schrieber and Lachmuth 2017), is not applied to the invasion of this species in Chiloé Island. This pattern of high genetic diversity in invasive mink populations has also been detected in feral populations from Poland (Zalewski et al. 2011), Argentina (Malerba et al. 2018), Spain (García et al. 2017), and Russia (Korablev et al. 2017) and it may be explained by introductions of many individuals and/or on multiple occasions (Facon et al. 2008). On the other hand, the genetic bottleneck was detected for both Chiloé and continental populations, which suggests that this phenomenon occurred before the invasion of the mink to Chiloé Island and probably is associated with its serial introduction into Magallanes, Aysén, and/or Los Lagosç in the south of Chile (Rozzi and Sherriffs 2003). ...
The American mink (Neovison vison) is an invasive species of mustelid, native to North America, first reported in Chiloé Island, Chile, in 2013. Due to the known threats of this exotic species on native and domestic fauna, as well as on humans (e.g., depredation and reservoir of diseases such as leptospirosis and COVID-19), great efforts have been made to control and eradicate their populations in Chiloé. Nonetheless, the genetic and epidemiological status of its current population is unknown. Here, we assessed genetic diversity, structure, and presence of Leptospira spp. in N. vison populations from Chiloé. To achieve this, we genotyped 61 individuals across 12 locations on the island and compared them to 30 individuals from 6 locations on the mainland using 12 microsatellite markers. High genetic diversity (He: 0.68), low genetic structure (FST: 0.021), high genetic flow (Nm: 7.43), and five shared genotypic groups were detected between continent and island mink populations. Although these results suggest multiple routes and origins of invasion from the continent to Chiloé, high migration rates detected between island and Pargua localities allow us to infer that a large number of individuals crossed the Chacao Channel. On the other hand, leptospirosis assays on 33 mink kidney samples using qPCR detected this pathogen with a prevalence of 18% in 42% of the localities sampled (6 individuals from 5 localities). We hope that this first population genetic and epidemiological report will be a useful tool for decision-making and the control of minks on Chiloé Island.
... However, recent studies provide evidence that the genetic paradox of invasion is to a large extent overrated (Rius et al. 2015). Many invasive populations show comparable or higher genetic diversity relative to native populations possibly owing to multiple introductions (Facon et al. 2008;Blumenfeld et al. 2021). In addition, loss in genetic diversity of invasive populations may mainly occur at neutral genetic markers which are not reflected in adaptive traits (Estoup et al. 2016). ...
The goldfish Carassius auratus complex is one of the most successfully invasive fish species on the Tibetan Plateau. However, little is known about the ploidy distribution of the invasive populations and their evolutionary dynamics. Here, using mitochondrial D-loop and eight microsatellites, we evaluated the genetic diversity and population structure of three invasive populations from Tibet and 12 native populations from six rivers including the Yangtze River and Yellow River which were assumed to be the sources by market survey. The proportions of diploids ranged from 0 to 61% in the three invasive populations. A total of 60 and 57 D-loop haplotypes were detected from 344 diploids and 838 triploids, respectively, with 28 haplotypes being shared. For diploids, the haplotype diversity (Hd: 0.600–0.655) and mean observed heterozygosity (HO: 0.871–0.888) of microsatellites of invasive populations were lower than those of source populations (Hd: 0.883–0.950, HO: 0.891–0.982). However, for triploids, invasive populations also had lower Hd values (0.617–0.816) but comparable HO values (0.900–0.933) than the source populations (Hd: 0.838–0.918, HO: 0.925–0.948). The structure analysis for diploids showed that all invasive individuals shaped one single genetic cluster which was separated from native individuals. For triploids, no genetic separation was observed between invasive and native populations. Our results demonstrated the difference in ploidy ratio among invasive populations may be related to wetlands’ open state, and the diploids rather than triploids of goldfish experienced obvious changes of genetic diversity and population structure during their invasion to Tibet.
... One unresolved question in invasion biology asks: given the profound reduction in genetic variation that accompanies many species introductions, how do invading populations have sufficient raw genetic material to adapt to novel environments (Allendorf & Lundquist 2003, Frankham 2005 In recent years, the prevalence of this so-called ‗invasion paradox' has been challenged (Estoup et al. 2016, Dlugosch and, with several studies failing to find evidence of reduced diversity in recently introduced populations (Roman and Darling 2007, Facon et al. 2008, Kolbe et al. 2004 see Kanuch et al. 2021). A common mechanism for maintaining high levels of genetic variation in invasive populations is admixture between multiple genetically distinct invading populations (Bock et al. 2015, Dlugosch and Parker 2008, Prentis et al. 2008, Rius and Darling 2014. ...
Biological introductions are unintended "natural experiments" that provide unique insights into evolutionary processes. Invasive phytophagous insects are of particular interest to evolutionary biologists studying adaptation, as introductions often require rapid adaptation to novel host plants. However, adaptive potential of invasive populations may be limited by reduced genetic diversity-a problem known as the "genetic paradox of invasions". One potential solution to this paradox is if there are multiple invasive waves that bolster genetic variation in invasive populations. Evaluating this hypothesis requires characterizing genetic variation and population structure in the invaded range. To this end, we assemble a reference genome and describe patterns of genetic variation in the introduced white pine sawfly, Diprion similis. This species was introduced to North America in 1914, where it has rapidly colonized the thin-needled eastern white pine (Pinus strobus), making it an ideal invasion system for studying adaptation to novel environments. To evaluate evidence of multiple introductions, we generated whole-genome resequencing data for 64 D. similis females sampled across the North American range. Both model-based and model-free clustering analyses supported a single population for North American D. similis. Within this population, we found evidence of isolation-by-distance and a pattern of declining heterozygosity with distance from the hypothesized introduction site. Together, these results support a single-introduction event. We consider implications of these findings for the genetic paradox of invasion and discuss priorities for future research in D. similis, a promising model system for invasion biology.
... Indeed, some classic examples of eco-evolutionary dynamics, such as Yoshida et al.'s (2003) predator-prey cycles driven by the 'rapid evolution' of clonal algae, could be easily reinterpreted as simple ecological dynamics in which the abundance of different algal 'species' changes. A similar issue arises in clonal multicellular organisms (e.g., parthenogenetic freshwater snails: Facon et al., 2008). Changes in species abundances and changes in phenotype frequencies generate the same type of effect, that is, changes in mean trait values. ...
Despite decades of research on the interactions between ecology and evolution, opportunities still remain to further integrate the two disciplines, especially when considering multispecies systems. Here, we discuss two such opportunities. First, the traditional emphasis on the distinction between evolutionary and ecological processes should be further relaxed as it is particularly unhelpful in the study of microbial communities, where the very notion of species is hard to define. Second, key processes of evolutionary theory such as adaptation should be exported to hierarchical levels higher than populations to make sense of biodiversity dynamics. Together, we argue that broadening our perspective of eco‐evolutionary dynamics to be more inclusive of all biodiversity, both phylogenetically and hierarchically, will open up fertile new research directions and help us to address one of the major scientific challenges of our time, that is, to understand and predict changes in biodiversity in the face of rapid environmental change.
... The intercontinental network of disturbed niches may facilitate the establishment of r-strategy alien populations (Davis 2005). These r-strategist populations or species are likely to be replaced by more competitive populations or species in later stages of the invasion (Facon et al. 2008). Pine species (Pinus spp.) that invade habitats undergoing strong disturbances, for example, were mainly characterized by three r-selected traits: short juvenile period, light seeds and short time intervals between breeding events (Rejmánek and Richardson 1996). ...
With the advent of the Anthropocene, biological invasions have reached an unprecedented level, and the number of species introductions is still increasing in an ever-changing world. Despite major advances in invasion science, significant debate and lack of clarity remain surrounding the determinants of success of introduced species, the magnitude and dimensions of their impact, and the mechanisms sustaining successful invasions. Empirical studies show divergent impacts of alien populations on ecosystems and contrasting effects of biotic and abiotic factors on the dynamics of alien populations, which hinders the creation of a unified theory of biological invasions. Compounding these issues is the plethora of hypotheses that aim to explain invasion success, which can be unclear and contradictory. We propose a synthesis that categorizes hypotheses along a timeline of invasion. We sorted invasion hypotheses along the invasion timeline, and considered population, community and ecosystem levels. This temporal sorting of invasion concepts shows that each is relevant at a specific stage of the invasion. Although concepts and empirical findings on alien species may appear contradictory, when mapped onto an invasion timeline, they may be combined in a complementary way. An overall scheme is proposed to summarise the theoretical dynamics of ecosystems subjected to invasions. For any given case study, this framework provides a guide through the maze of theories and should help choose the appropriate concepts according to the stage of invasion.
... The populations of non-native species are traditionally thought to experience a significant reduction in genetic diversity relative to their source populations due to founder effects and the arrival of only a few individuals during the introduction stage of the invasion [64]. However, more and more studies using neutral molecular markers are showing that such species do not necessarily present a significant loss of genetic diversity, often resulting from multiple introductions in the novel range or a single introduction of a large number of individuals [10,[65][66][67][68][69]. ...
The Western conifer seed bug, Leptoglossus occidentalis, is native to North America and has already been considered a significant pest in several European countries since its first observation in Italy in 1999. In Spain and Portugal, it was recorded for the first time in 2003 and 2010, respectively, and its impact on Stone Pine (Pinus pinea) is of major concern. Before developing control measures for this insect pest, it is paramount to clarify its spatiotemporal dynamics of invasion. Therefore, in this study, we aimed to (a) characterise the genetic structure and diversity and (b) invasion pathways of L. occidentalis populations in the Iberian Peninsula. To do so, specimens of L. occidentalis were collected at fourteen sites widely distributed within the Iberian Peninsula. We used mtDNA sequences of Cytochrome b and eleven microsatellite markers to characterise the genetic diversity
and the population structure in the Iberian Peninsula. Our genetic results combined with the observational dates strongly support a stratified expansion of L. occidentalis invasion in the Iberian
Peninsula proceeding from multiple introductions, including at least one in Barcelona, one in Valencia, and one in the west coast or in the Southeastern region.
... A similar issue arises in clonal multicellular organisms (e.g. parthenogenetic freshwater snails: Facon et al. 2008). Changes in species abundances and changes in phenotype frequencies generate the same type of effect, i.e. changes in mean trait values. ...
Despite growing interactions between ecology and evolution, there still remain opportunities to further integrate the two disciplines, especially when considering multispecies systems. Here, we discuss two such opportunities. First, we suggest to relax the focus on the distinction between evolutionary and ecological processes. This focus is particularly unhelpful in the study of microbial communities, where the very notion of species is hard to define. Second, we propose that key processes of evolutionary theory such as adaptation should be exported to hierarchical levels higher than populations to make sense of biodiversity dynamics. Together, we argue that broadening our perspective of eco-evolutionary dynamics to be more inclusive of all biodiversity, both phylogenetically and hierarchically, will open up fertile new research directions and help us to address one the major scientific challenges of our time, i.e. to understand and predict changes in biodiversity in the face of rapid environmental change.
... Particularly, an intraspecific genetic admixture may benefit introduced populations via (1) an increase in genetic variation, which provides a larger pool of raw material for adaptive evolution; (2) the emergence of novel or transgressive phenotypes through previously unexplored allele and gene combinations [6,8,9]; (3) heterosis; and (4) the masking or purging of deleterious mutations; the latter process may reduce potentially negative effects of genetic bottlenecks and inbreeding [6,10,11]. The effect of multi-source introductions has been investigated for plants [12][13][14], mollusks [15,16], arthropods [17,18], and lizards [19][20][21]. Most of these studies indicate an increase in genetic diversity in introduced versus source populations, but some reports also show a decrease in genetic diversity in mixed populations resulting from the admixture of geographically distant populations [4,13,14]. ...
Translocations and introductions are important events that allow organisms to overcome natural barriers. The genetic background of colonization success and genetic consequences of the establishment of populations in new environments are of great interest for predicting species’ colonization success. The wild boar has been introduced into many parts of the world. We analyzed sequences of the mitochondrial-DNA control region in the wild boars introduced into the Ural region and compared them with sequences from founder populations (from Europe, the Caucasus, Central Asia, and the Far East). We found that the introduced population has high genetic diversity. Haplotypes from all the major phylogenetic clades were detected in the analyzed group of the animals from the Urals. In this group, no haplotypes identical to Far Eastern sequences were detectable despite a large number of founders from that region. The contribution of lineages originating from Eastern Europe was greater than expected from the proportions (%) of European and Asian animals in the founder populations. This is the first study on the genetic diversity and structure of a wild boar population of mixed origin at the northern periphery of this species’ geographical range.
... Novel or transgressive phenotypes are commonly defined as traits or combinations of traits that fall outside the range of variation of parental species (Rieseberg et al. 2003b;Bell and Travis 2005;Stelkens et al. 2009). Transgressive phenotypes are common in both plants and animals and have so far been demonstrated for several fitness-related traits, including morphology (skull morphology in fish, Stelkens et al. 2009; wing morphology in butterflies, Mérot et al. 2020), physiology (temperature tolerance in copepods, Pereira et al. 2014), life history (number and size of offspring in snails, Facon et al. 2008), and behavioral traits (mating behavior in fruit flies, Ranganath and Aruna 2003; foraging behavior in fish, Selz and Seehausen 2019;Feller et al. 2020). Different mechanisms have been proposed to explain how recombination of parental genomes can result in novel traits (Rieseberg et al. 2003b;Bell and Travis 2005;Stelkens et al. 2009; Thompson et al. 2021). ...
Hybridization can promote phenotypic variation and often produces trait combinations distinct from the parental species. This increase in available variation can lead to the manifestation of functional novelty when new phenotypes bear adaptive value under the environmental conditions in which they occur. While the role of hybridization as a driver of variation and novelty in traits linked to fitness is well recognized, it remains largely unknown whether hybridization can fuel behavioural novelty by promoting phenotypic variation in brain morphology and/or cognitive traits. To address this question, we investigated the effect of hybridization on brain anatomy, learning ability, and cognitive flexibility in first‐ and second‐generation hybrids of two closely related fish species (Poecilia reticulata and P. wingei). Overall, we found that F1 and F2 hybrids showed intermediate brain morphology and cognitive traits compared to parental groups. Moreover, as phenotypic dispersion and transgression was low for both brain and cognitive traits, we suggest that hybridization is not a strong driver of brain anatomical and cognitive diversification in these Poeciliidae. To determine the generality of this conclusion, hybridization experiments with cognitive tests need to be repeated in other families. This article is protected by copyright. All rights reserved
... Some mechanisms, such as gene recombination and invasion evolution acting on individual traits and trait combinations, have been shown to drive the production of key genetic characteristics after interspeci c hybridization [13,18]. In the context of intraspeci c hybridization, genetic admixture has been shown to greatly increase genetic phenotypic variation in invasive populations of plants [19]. For example, the grain weight per panicle and grain yield in a millet hybrid population were higher than those in their parents [20]. ...
Background
Changes in population heterozygosity and genetic diversity play important roles in mediating life history traits of organisms; these changes often lead to phenotypic evolution in offspring, which become superior to their parents. In the present study, we examined phenotypic differentiation, the intestinal microbiome composition and metabolism in the oriental fruit fly (Bactrocera dorsalis) by comparing an inbred (monophyletic) native population and an outbred (mixed) invasive population.
Results
The results showed that the outbred population of B. dorsalis had significantly higher biomass, adult longevity, and fecundity than the inbred population. Additionally, intestinal microflora analysis revealed that both Diutina rugosa and Komagataeibacter saccharivorans were significantly enriched in the outbred population with higher genetic heterozygosity. D. rugosa enrichment altered amino acid metabolism in the intestinal tract, and supplementing essential amino acids (e.g., histidine and glutamine) in the diet led to an increase in pupal weight of the outbred population. Additionally, transcriptome analysis revealed that the HSPA1S gene was significantly downregulated in the outbred population. HSPA1S was involved in activation of the JNK-MAPK pathway through negative regulation, caused the upregulation of juvenile hormone (JH), and led to an increase in biomass in outbred flies.
Conclusion
In conclusion, the outbred population had an altered intestinal microbe composition, mediating metabolism and transcriptional regulation, leading to phenotypic differentiation; this may be a potential mechanism driving the global invasion of B. dorsalis. Thus, multiple introductions could lead to invasiveness enhancement in B. dorsalis through population mixing, providing preliminary evidence that changes in the intestinal microbiome can promote biological invasion.
... As such, there does not appear to be clear and consistent morphological traits shared by specimens within genotypes that allows them to be differentiated between morphs. While Facon et al. (2008) found different invading genotypes to have identical morphologies in Martinique, West Indies, this is not a universal truth. For example, Van Bocxlaer et al. (2015) found Asian invasive lineages to resemble each other in overall shell morphology, despite belonging to deeply divergent clades. ...
Melanoides tuberculata (Müller, 1774) is a widely distributed aquatic gastropod, primarily found in tropical regions, which has also invaded geothermally heated waters in temperate regions. The spread of M. tuberculata globally has primarily been in association with the aquarium trade and aquatic plants. In New Zealand, M. tuberculata is known from both the aquarium trade and from one non-indigenous population in a geothermal stream. To date, the origins of M. tuberculata in the aquarium trade in New Zealand—or elsewhere—has not been systematically examined genetically, and it has not been confirmed whether New Zealand’s non-indigenous population is genetically similar to, or originated from, individuals sold in aquarium stores. We examined the origins of New Zealand M. tuberculata, in the aquarium trade, and in the established non-indigenous population using COI marker sequences. Representatives of M. tuberculata in New Zealand have not originated from a single source; two distinct genetic clades were identified for individuals, with the origins of each inferred to be from Asia and Africa. The non-indigenous population and individuals sourced from one private aquarium owner were found to originate in Asia, and are genetically similar to those collected from Singapore, one of the most significant countries globally for the culturing and distribution of aquarium species. The remaining collections, from a display aquarium and three online suppliers in various New Zealand locations, were most similar genetically to populations native to Lake Malawi and Tanganyika, and non-indigenous populations from Australia. Overall, as M. tuberculata is an obligate parthenogen, each independently introduced clone may be considered a distinct non-indigenous taxon. We recommend further systematic genetic analyses of individuals in the aquarium trade elsewhere, to assess more fully the diversity and origins of Melanoides being transported in the aquarium trade.
... Novel or transgressive phenotypes are commonly defined as traits or combinations of traits that fall outside the range of variation of parental species (Rieseberg et al. 2003b;Bell and Travis 2005;Stelkens et al. 2009). Transgressive phenotypes are common in both plants and animals and have so far been demonstrated for several fitness-related traits, including morphology (skull morphology in fish, Stelkens et al. 2009; wing morphology in butterflies, Mérot et al. 2020), physiology (temperature tolerance in copepods, Pereira et al. 2014), life-history (number and size of offspring in snails, Facon et al. 2008), and behavioural traits (mating behaviour in fruit flies, Ranganath and Aruna 2003; foraging behaviour in fish, Selz and Seehausen 2019;Feller et al. 2020). Different mechanisms have been proposed to explain how recombination of parental genomes can result in novel traits (Rieseberg et al. 2003b;Bell and Travis 2005;Stelkens et al. 2009; Thompson et al. 2021). ...
Hybridization can promote phenotypic variation and often produces trait combinations distinct from the parental species. This increase in available variation can lead to the manifestation of functional novelty when new phenotypes bear adaptive value under the environmental conditions in which they occur. While the role of hybridization as a driver of variation and novelty in traits linked to fitness is well recognized, it remains largely unknown whether hybridization can fuel behavioural novelty by promoting phenotypic variation in brain morphology and/or cognitive traits. To address this question, we investigated the effect of hybridization on brain anatomy, learning ability, and cognitive flexibility in first- and second-generation hybrids of two closely related fish species (Poecilia reticulata and P. wingei). Overall, we found that F1 and F2 hybrids showed intermediate brain morphology and cognitive traits compared to parental groups. Moreover, as phenotypic dispersion and transgression was low for both brain and cognitive traits, we suggest that hybridization is not a strong driver of brain anatomical and cognitive diversification in these Poeciliidae. To determine the generality of this conclusion, hybridization experiments with cognitive tests need to be repeated in other families.
... Interbreeding capabilities of various nematode strains has implications for the introduction of the biological control nematode strain. Admixture has the potential advantage of increased hybrid fitness due to selection of favourable phenotypes (Facon et al., 2008;Szűcs et al., 2012;Szűcs et al., 2019). However, studies of the long-term impact of admixture on population fitness are lacking, and where they exist, results are equivocal (Garnas, 2016(Garnas, , 2018. ...
Deladenus siricidicola is a principal biological control agent used to suppress populations of the globally invasive pine pest, the woodwasp Sirex noctilio. Previous studies have reported low genetic diversity in D. siricidicola populations in biological control programs in the Southern Hemisphere and identified two additional, distinct lineages in North America and Spain. In this study, we tested the ability of these three lineages to interbreed and produce viable offspring. We used microsatellite markers to confirm admixture in offspring. Secondly, we compared growth rates among parental and admixed replicates on four isolates of the Amylostereum areolatum fungus on which nematodes typically feed in their asexual, non-parasitic phase. We show that all the lineages were capable of interbreeding and that admixture was asymmetric (i.e., skewed towards one of the parents). The offspring from one of the crosses showed significant variation in growth rate on different isolates of A. areolatum, compared to the parental isolates, but specifically on the slowest growing fungal isolate. Our results pave the way for the strategic introduction of genetic diversity into biological control programs and also inform expectations of accidental introductions of D. siricidicola into new regions.
... In addition one gastropod of subclass Neritimorpha, and one bivalve (family Sphaeridae) are represented. We considered six morphotypes of the caenogastropod Melanoides tuberculata and treated them as separate metapopulations because they reproduce parthenogenetically, and each of them represents a morphological and genetic clone with its own invasion history in the islands (Facon et al., 2003(Facon et al., , 2008. Prior to the 1970s, the archipelago harbored a relatively stable number of native snail species, but invasive species have appeared and settled since then (Pointier, 1976;Pointier & Augustin, 1999;Pointier et al., 2011). ...
Characterizing the diversity of demographic strategies among species can inform research in topics such as trait syndromes, community stability, coexistence, and ecological succession. However, this diversity can depend on the spatial scale considered: at the landscape scale, species often form metapopulations, that is sets of local, sometimes short‐lived, populations, inhabiting discrete habitat patches. Metapopulation dynamics are most frequently analyzed in individual species or pairs of interacting species because of the large amount of data required for multiple species, and because species vary in their perceptions of what constitutes a favorable or unfavorable habitat. Here we evaluate, using a case study, whether a metapopulation model can be used to generate accurate estimates of demographic parameters and to describe the diversity of dynamics, responses to environment, and prospects of long‐term persistence in a guild of species inhabiting a common fragmented landscape. We applied this approach to a guild of 22 mollusk species that inhabit freshwater habitats on two islands of Guadeloupe, to compare metapopulation dynamics among species. We analyzed a 15‐year time series of occupancy records for 278 sites using a multistate occupancy model that estimated colonization and extinction rates as a function of site‐specific and year‐specific environmental covariates, then used model results to simulate future island metapopulation dynamics. Despite the diverse array of metapopulation trajectories—a mix of species with either stable, increasing, declining, or fluctuating metapopulations—and the inherent challenges associated with such data (e.g., imperfect detection, spatial and temporal heterogeneity), our model accurately captured among‐patch variation in suitability for many mollusk taxa. The dynamics of rare species or species with habitat preferences not fully captured by the retained set of covariates were less well described. For several species, we detected a negative correlation between extinction and colonization. This variation in habitat suitability created species‐specific extinction‐resistant pockets in the landscape. Our comparative analysis also revealed that species had distinct strategies for metapopulation dynamics, such as “fast‐turnover” species with both a high proportion of occupied sites and a high rate of site extinction in the landscape.
... Non-native species can be invasive in one region, but not in others (Zenni and Nuñez, 2013;Gallagher et al., 2015). Factors such as number of introductions, number of source populations, and other factors that contribute to genetic diversity shaping invasion success (Stepien et al. 2005;Facon et al. 2008;Dlugosch et al. 2015). As such, an important aspect of understanding invasive species dynamics is reconstructing the potentially complex history of their introduction into the invaded habitat (Sakai et al., 2001;Lee, 2002), often through the use of genetic data . ...
Seagrasses occur worldwide, and are essential primary producers that uptake carbon dioxide, fix nutrients, stabilize sediments, prevent reef degradation, filter bacteria, provide food and nursery habitats to marine organisms. When seagrass meadows disappear, carbon is released back into the water column, sediments get stirred, water clarity decreases, and reefs become infected, with negative impacts on marine biodiversity and maritime economy. My thesis utilizes multidisciplinary ecology and evolutionary biology approaches to better understand the biology of seagrasses, particularly an invasive seagrass, to help improve management strategies for seagrass conservation.
Seagrasses frequently display distinct depth distribution, although drivers of these patterns can be spatially and temporally variable. Chapter 1 examines the factors that influence the depth distribution of a circumtropical seagrass, Halophila decipiens. While H. decipiens can grow in waters as shallow as 1 m, in Moorea, French Polynesia we only found it in waters deeper than 6.4 m. To understand why H. decipiens did not grow in shallower habitats, we transplanted it into 3 habitats: the existing seagrass bed (control), just outside the seagrass bed, and shallower habitat adjacent to a fringing coral reef. Results showed that growth was not significantly different between the seagrass bed and just outside of the seagrass bed; however, its growth was significantly reduced when adjacent to the reef. We then transplanted seagrass into a shallower reef site with and without herbivore exclusion cages, and the results showed that H. decipiens grew best when herbivores were excluded, but lost growth when herbivores were allowed access. These results indicate that H. decipiens can grow in shallow habitats adjacent to reefs, but herbivory pressure from the reef limits its depth distribution.
Seagrass meadows are in decline around the world. Biological invasions can magnify threats to seagrass ecosystems with detrimental consequences to seagrass biodiversity. In Chapter 2, I used mesocosm experiments to investigate the interactions between the invasive seagrass Halophila stipulacea and native seagrasses to determine whether species interactions can drive, prevent, or facilitate invasions in both the Mediterranean and Caribbean Sea. In the Caribbean, invasive H. stipulacea increased in growth when grown with the native Syringodium filiforme, and lost shoots when grown alone, while S. filiforme only increased in shoots when grown alone. This pattern was the same in the Mediterranean; when invasive H. stipulacea grew with the native Cymodocea nodosa, it gained more shoots than when grown alone, but C. nodosa only did better when grown alone. Results suggest that the invasive seagrass H. stipulacea can drive its own success by negatively affecting native seagrasses and benefiting from that negative interaction. This novel example of native species facilitating the success of an invasive provides one possible mechanism for the widespread success of this invasive species.
Mechanisms that influence invasion success can further be understood by understanding how it was introduced to a specific region. In Chapter 3, I used genomic tools to reconstruct the origins of the globally invasive seagrass Halophila stipulacea in the Mediterranean and Caribbean Seas. While H. stipulacea almost certainly invaded the Mediterranean from native populations in the Red Sea through the Suez Canal, it is unclear whether the Caribbean invasion represents stepping stone colonization from the Mediterranean, an independent introduction from the native range, or an admixture from multiple native/invasive populations. To test these hypotheses, we examined population genetic structure and genetic diversity from multiple locations spanning across the native, historic, and recent invasive ranges of H. stipulacea, including the Indian Ocean and Red Sea, Mediterranean Sea, and the Caribbean Sea, respectively. Data from 524 SNP loci and restrictive, 45 SNP loci at >10x coverage revealed significant genetic structure among all five regions. The analyses revealed that the widespread invasion of H. stipulacea into the Caribbean Sea came from multiple introductions originating from the Mediterranean. This work provides a baseline for the distribution of the invasive H. stipulacea in the Caribbean and may help predict how to minimize detrimental impacts of a non-indigenous seagrass across its invaded ranges.
Life history differences can provide a link in invasion potential and dispersal. In Chapter 4 I investigated the life history of seagrass Halophila stipulacea in the Caribbean. Reports of asexual and sexual reproduction are common in its native range, with sexual reproduction being less common in the Mediterranean Sea. Here we make the first report of H. stipulacea male flowers in the Caribbean and suggest that asexual fragmentation is the main strategy of expansion. These findings have important implications for the future dispersal, survival, and maintenance of the non-native populations in the Caribbean.
... We indirectly observe this in AEA regions' geographically restricted haplotype-sharing patterns ( . Patterns that are similar to the ones we have reported here for A. thaliana have been suggested for other systems, albeit mostly based on limited genetic information and without the benefit of being able to infer ancestry along each chromosome (Kolbe et al. 2004;Lavergne and Molofsky 2007;Facon et al. 2008;Smith et al. 2020). ...
Large-scale movement of organisms across their habitable range, or migration, is an important evolutionary process that can shape genetic diversity and influence the adaptive spread of alleles. While human migrations have been studied in great detail with modern and ancient genomes, recent anthropogenic influence on reducing the biogeographical constraints on the migration of non-native species has presented opportunities in several study systems to ask the questions about how repeated introductions shape genetic diversity in the introduced range. We present an extensive overview of population structure of North American Arabidopsis thaliana by studying a set of 500 whole-genome sequenced and over 2,800 RAD-seq genotyped individuals in the context of global diversity represented by Afro-Eurasian genomes. We use methods based on haplotype and rare-allele sharing as well as phylogenetic modeling to identify likely sources of introductions of extant N. American A. thaliana from the native range in Africa and Eurasia. We find evidence of admixture among the introduced lineages having increased haplotype diversity and reduced mutational load. We also detect signals of selection in immune-system related genes that may impart qualitative disease resistance to pathogens of bacterial and oomycete origin. We conclude that multiple introductions to a non-native range can rapidly enhance the adaptive potential of a colonizing species by increasing haplotypic diversity through admixture. Our results lay the foundation for further investigations into the functional significance of admixture.
... In some cases, alien species have been introduced to the same location on multiple occasions from different sources, creating genetic combinations of individuals that have not previously existed (Kolbe et al. 2004). Such admixture can enhance fitness through hybrid vigour or increased genetic diversity (Barker et al. 2019;Dlugosch, Parker 2008;Facon et al. 2008;Hirsch et al. 2017;Rius, Darling 2014) or reduce fitness through outbreeding depression (Rhymer, Simberloff 1996). It is unclear how frequently genetic factors are intrinsic to the success or otherwise of invasive species (Barker et al. 2019;Rius, Darling 2014) although propagule pressure (something that will affect the levels of genetic diversity within an invader) is one of the few acknowledged general characteristics of successful invaders (Bock et al. 2015). ...
The introduction of species into new environments provides the opportunity for the evolution of new forms through admixture and novel selection pressures. The common brushtail possum, Trichosurus vulpecula vulpecula from the Australian mainland and T.v.fuliginosus from Tasmania, were introduced multiple times to New Zealand from Australia to become one of New Zealand's most significant pests. Although derived from two sub-species, possums in New Zealand are generally considered to be a single entity. In a previous analysis, we showed that possums in the Hawkes Bay region of New Zealand appeared to consist of at least two overlapping populations. Here, we extend that analysis using a genotype-by-sequencing approach to examine the origins and population structure of those possums and compare their genetic diversity to animals sampled from Australia. We identify two populations of each subspecies in Hawkes Bay and provide clear evidence of a contact zone between them in which a hybrid form is evident. Our analysis of private alleles shows higher rates of dispersal into the contact zone than away from it, suggesting that the contact zone functions as a sink (and hence as a barrier) between the two subspecies. Given the widespread and overlapping distribution of the two subspecies across both large islands in New Zealand, it is possible that many such contact zones exist. These results suggest an opportunity for a more targeted approach to controlling this pest by recognising sub-specific differences and identifying the contact zones that may form between them.
... Hence, intraspecific hybridization between the two lineages could occur in this location. However, detailed statistical analyses using Genetic admixture through multiple introductions can provide gains of genetic diversity within introduced populations, thus increasing their fitness as well as their adaptive potential (Barker et al., 2017;Dlugosch & Parker, 2008;Facon et al., 2008;Keller & Taylor, 2010;Kolbe et al., 2004Kolbe et al., , 2007. Additionally, admixture can create new genotypes/phenotypes, increasing the adaptive potential of the colonizing populations (Nolte et al., 2009;Rius & Darling, 2014;van Boheemen et al., 2017;Verhoeven et al., 2011). ...
Introduced populations of invasive organisms cope with novel environmental challenges, while having reduced genetic variation caused by founder effects. The mechanisms associated with this “genetic paradox of invasive species” has received considerable attention, yet few studies have examined the genomic architecture of invasive species. Populations of the heart node ant Cardiocondyla obscurior belong to two distinct lineages, a New World lineage so far only found in Latin America and a more globally distributed Old World lineage. In the present study, we use population genomic approaches to compare populations of the two lineages with apparent divergent invasive potential. We find, that the strong genetic differentiation of the two lineages began at least 40,000 generations ago and that activity of transposable elements (TEs) contributes significantly to the divergence of both lineages, possibly linked to the very unusual genomic distribution of TEs in this species. Further, we show that introgression from the Old World lineage is a dominant source of genetic diversity in the New World lineage, despite the lineages’ strong genetic differentiation. Our study uncovers mechanisms underlying novel genetic variation in introduced populations of C. obscurior that could contribute to the species’ adaptive potential.
... On the other hand, homogenised standing genetic variation across the nonnative distribution may indicate low genetic diversity, which could compromise the response of non-native populations to new environmental conditions (Keller and Taylor 2010). Multiple introductions of genetically distinct sources thus acquire an important role by adding diversity to founding populations that is liable to be enhanced through admixture and sexual reproduction (Facon et al. 2008;Uller and Leimu 2011). However, mtDNA variation represents but a minimal fraction of an organismal genetic diversity. ...
Biological invasions via translocations are a textbook case of globalization’s impact on species distributions. Human-mediated transport helps species to overcome natural spatial boundaries and establish populations, often from a small number of individuals, in ecosystems previously unreachable through natural range expansion. The result is a discontinuous species distribution, with connectivity between the native and non-native range dependent on the recurrence of human-mediated species movement. The genetic diversity of introduced individuals represents a random fraction of the original diversity in the native range, but because connectivity is lost, non-native populations are bound to evolve independently. As a result, translocations can reshuffle genetic diversity in non-native populations, and thus, differentiation patterns arising after introduction may constitute the first step of novel evolutionary trajectories. By performing a meta-analysis on 5516 mitochondrial sequences of 20 different species, we explored whether life- and evolutionary history could explain differentiation among non-native populations of recently translocated organisms. We observed a general pattern consisting of reduced differentiation among non-native populations whose introduction derived from a single and intentional translocation, suggesting that these human actions play a role in reshaping genetic variance in non-native ranges. Additionally, we found geographic distance to be a poor predictor of population differentiation on the non-native range when compared to averaged evolutionary distances—the opposite being true for the native range—reinforcing connectivity break imposed by translocation events. Understanding the factors driving the distribution of genetic diversity upon translocations might not only facilitate the development of plans to mitigate the dispersal of invasive species but also to explore the emergence of novel evolutionary trajectories.
... In addition to the genome-wide SNP data set, we genotyped each individual's mitochondrial genome. Because mitochondrial haplotypes are maternally inherited and do not undergo recombination, they can be utilized to estimate the number of colonization events occurring during range expansions associated with biological invasions (Facon et al., 2008b;Kolbe et al., 2004;Michaelides et al., 2018). We mapped raw sequence reads, for each individual, to an assembled mitochondria of Z. indianus (assembled from same isofemale line from Florida used for the reference genome described above; Supporting Information Data) following the same procedure described above for the nuclear genome. ...
Introduced species have become an increasingly common component of biological communities around the world. A central goal in invasion biology is therefore to identify the demographic and evolutionary factors that underlie successful introductions. Here we use whole genome sequences, collected from populations in the native and introduced range of the African fig fly, Zaprionus indianus, to quantify genetic relationships among them, identify potential sources of the introductions, and test for selection at different spatial scales. We find that geographically widespread populations in the western hemisphere are genetically more similar to each other than to lineages sampled across Africa, and that these populations share a mixture of alleles derived from differentiated African lineages. Using patterns of allele‐sharing and demographic modelling we show that Z. indinaus have undergone a single expansion across the western hemisphere with admixture between African lineages predating this expansion. We also find support for selection that is shared across populations in the western hemisphere, and in some cases, with a subset of African populations. This suggests either that parallel selection has acted across a large part of Z. indianus’s introduced range; or, more parsimoniously, that Z. indianus has experienced selection early on during (or prior‐to) its expansion into the western hemisphere. We suggest that the range expansion of Z. indianus has been facilitated by admixture and selection, and that management of this invasion could focus on minimizing future admixture by controlling the movement of individuals within this region rather than between the western and eastern hemisphere.
... The degree to which genetic diversity is reduced may be limited when the initial colonizing force is large, when the introduced population is subsequently reinvaded by additional individuals during multiple introduction events, and/ or when the introduced population is invaded by individuals from several genetically distinct source populations (Facon et al., 2006). Sometimes, when there are several introductions from different source populations and these interbreed within an invasive population, genetic diversity may even be higher within this population than its native source population(s) (Facon et al., 2008). In contrast, the bridgehead effect may result in a severe loss of diversity, as subsequent introductions arise from an already depauperate introduced population. ...
As native ranges are often geographically structured, invasive species originating from a single source population only carry a fraction of the genetic diversity present in their native range. The invasion process is thus often associated with a drastic loss of genetic diversity resulting from a founder event. However, the fraction of diversity brought to the invasive range may vary under different invasion histories, increasing with the size of the propagule, the number of re‐introduction events, and/or the total genetic diversity represented by the various source populations in a multiple‐introduction scenario. In this study, we generated a SNP dataset for the invasive termite Reticulitermes flavipes from 23 native populations in the eastern United States and six introduced populations throughout the world. Using population genetic analyses and approximate Bayesian computation Random Forest, we investigated its worldwide invasion history. We found a complex invasion pathway with multiple events out of the native range and bridgehead introductions from the introduced population in France. Our data suggest that extensive long‐distance jump dispersal appears common in both the native and introduced ranges of this species, likely through human transportation. Overall, our results show that similar to multiple introduction events into the invasive range, admixture in the native range prior to invasion can potentially favor invasion success by increasing the genetic diversity that is later transferred to the introduced range.
... In light of the unprecedented number of introductions of non-native species (Mack et al., 2000), one of the most pressing research needs for evolutionary biologists and ecologists is to identify the factors that influence the establishment of species that have negative ecological and economic impacts (Suarez & Tsutsui, 2008). Multiple introductions (Dlugosch & Parker, 2008), including cryptic ones (Roman, 2006), are thought to play an important role in providing the diversity required to overcome genetic bottlenecks associated with the establishment of populations in novel ecosystems (Darling et al., 2008;Facon et al., 2008). However, when multiple geographically disjunct populations of an invasive species become established, it is often unclear whether the species is a serial invader (i.e., each population was introduced independently) or whether the separate populations represent establishment from within the invasive regions under a "stepping stone" model (see Cerwenka et al., 2014;Lombaert et al., 2010;Oficialdegui et al., 2019;Tonione et al., 2011 for examples). ...
Reconstructing the geographic origins of nonnative species is important for studying the factors that influence invasion success, however; these analyses can be constrained by the amount of diversity present in the native and invaded regions, and by changes in the genetic background of the invading population following bottlenecks and/or hybridization events. Here we explore the geographical origins of the invasive winter moth (Operopthera brumata L.) that has caused widespread defoliation to forests, orchards, and crops in Nova Scotia, British Columbia, Oregon, and the northeastern United States. It is not known whether these represent independent introductions to North America, or a “stepping stone” spread among regions. Using a combination of Bayesian assignment and approximate Bayesian computation methods, we analyzed a population genetic dataset of 24 microsatellite loci. We estimate that winter moth was introduced to North America on at least four occasions, with the Nova Scotian and British Columbian populations likely being introduced from France and Sweden, respectively; the Oregonian population likely being introduced from either the British Isles or northern Fennoscandia; and the population in the northeastern United States likely being introduced from somewhere in Central Europe. We discuss the impact of genetic bottlenecks on analyses meant to determine region of origin.
... Il faut en outre noter que le tirage aléatoire des individus dans la population native peut mener à des modifications des proportions relatives de certains allèles, voire à l'expression d'allèle récessifs rares dans la population native (Willis & Orr 1993) ou à la purge d'allèles délétères (Facon et al, 2011 ;Estoup et al, 2016 ; Encadré 3), et donc conduire à l'expression de paramètres de diversité différents entre les populations natives et introduites. Les introductions multiples permettent donc de combiner des niveaux de variation inédits avec de nouvelles associations génétiques (Roman & Darling, 2007 ;Dlugosh & Parker, 2008 ;Facon et al, 2008 ;Kerdelhué et al, 2014). ...
Le capricorne asiatique Anoplophora glabripennis est un exemple d’insecte ayant bénéficié du commerce international depuis l’Asie pour envahir une partie de l’Amérique du Nord où il est présent depuis les années 1990, et de l’Europe où sa présence a été détectée au début des années 2000. Cette espèce hautement polyphage se développe dans les arbres urbains et peut causer leur mort, soulignant l’importance du contrôle de sa population. En utilisant une approche pluridisciplinaire sur la base du modèle A. glabripennis, cette thèse vise à apporter de nouveaux éléments pour la compréhension globale des invasions biologiques. Dans un premier temps, j’ai cherché à retracer son cheminement dans le monde. Dans un second temps, j’ai cherché à savoir si certaines de ses caractéristiques biologiques avaient contribué au succès de son invasion. Enfin, j’ai abordé la question de l’impact écologique d’A.glabripennis en me focalisant sur les modifications de la faune de xylophages que sa présence aurait pu entrainer.Les résultats obtenus au cours de cette thèse ont permis de mettre en évidence une invasion complexe incluant plusieurs introductions ainsi qu’un scénario de tête de pont entre l’Amérique du Nord et l’Europe. Il apparait également que certains traits de l’espèce ont contribué à modeler son schéma de distribution. Sa résistance au stress thermique notamment a probablement favorisé son installation sous des climats variés. Par ailleurs, la dispersion naturelle d’A. glabripennis semble très limitée, mais mes résultats indiquent que l’espèce n’est pas restreinte par ses capacités physiologiques pour disperser. Enfin, l’étude préliminaire des faunes envahies ne révèle pas pour le moment d’effet de l’espèce sur les autres Cérambycidés.Au regard des autres cas d’invasion documentés, le cas d’A.glabripennis souligne donc la diversité des caractéristiques des espèces devenant invasives, et confirme la difficulté d’en dresser un portrait type.
... Similarly, human actions can result in intraspecific admixture by allowing previously separated populations of the same species to interbreed. Intraspecific admixture may happen through multiple sequential introductions from different source populations into a single area (Dlugosch & Parker, 2008), or through secondary contact between populations initially introduced to different areas of the invaded range (Facon et al., 2008;Rosenthal et al., 2008). Although intraspecific admixture could slow down or reverse local adaptation (Verhoeven et al., 2011), it may also facilitate invasion by generating evolutionary novelty, increasing genetic variation, and causing heterosis by alleviating genetic load (Ellstrand & Schierenbeck, 2000). ...
... présentée dans l'encadré 2. Le succès d'invasion peut également dépendre de la capacité des organismes à s'adapter à leur nouvel environnement (Gilchrist and Lee, 2007). En effet, le potentiel évolutif est souvent perçu comme déterminant dans le succès des invasions (Estoup et al., 2016;Facon et al., 2008). Par la suite, nous nous intéresserons aux invasions biologiques principalement dans le cadre des mécanismes liés à l'adaptation des organismes à leur nouvel environnement. ...
Comprendre comment évolue l’adéquation entre le phénotype des organismes et leur environnement est un enjeu majeur de la biologie évolutive, notamment dans le contexte des changements globaux. Dans le cadre de cette thèse, j’ai étudié les réponses adaptatives aux pressions environnementales, à différentes échelles géographiques et temporelles de Drosophila suzukii, une espèce généraliste envahissante ravageuse des cultures fruitières. J’ai utilisé des méthodes de génétique évolutive combinant génomique des populations et approches expérimentales centrées sur l’étude des traits d’histoire de vie. A partir d’une analyse d’association entre la différenciation génétique et le statut natif ou invasif de 22 populations échantillonnées à travers le monde, j’ai identifié des gènes candidats présentant des variations alléliques fortement associées à l’invasion de D. suzukii. A une échelle temporelle et géographique plus fine (i.e., au sein d’une région de l’aire envahie), je me suis intéressée à la réponse adaptative de cette espèce à une disponibilité des plantes hôtes hétérogène dans l’espace et dans le temps. En utilisant des approches d’évolution expérimentale, j’ai montré que des patrons d’adaptation locale aux fruits hôtes émergent en moins de 30 générations en laboratoire. De manière surprenante, j’ai détecté un patron semblable d’adaptation locale aux fruits hôtes dans des populations naturelles ayant passé moins de quatre générations sur un même fruit. La rapidité des réponses adaptatives observées in natura soulève de nombreuses questions sur la dynamique des processus influençant l’évolution de l’adaptation locale dans un environnement hétérogène dans l’espace et dans le temps à une échelle géographique fine. Les travaux de cette thèse ont permis d’apporter un ensemble d’éléments conceptuels et méthodologiques novateurs pour améliorer notre compréhension de la dynamique de l’adaptation des insectes phytophages à leurs plantes hôtes et des changements évolutifs ayant lieu au cours d’une invasion.
... However, observations of some alien species invasions have shown evidence of introduced populations without reduced genetic variability [3,5,7,8]. It is possible that genetic diversity in introduced populations is not lost when large numbers of animals are present or multiple introductions occur (propagule pressure) [9,10]. ...
Genetic characteristics play an important role in alien species for achieving high adaptation and rapid evolution in a new environment. The American mink (Neovison vison) is one of the best-known and most widespread invasive species that has successfully invaded the Eurasian mainland over quite a short period, including most parts of northeastern China. However, genetic information on farmed and feral American mink populations introduced in China is completely lacking. In this study, we combined mitochondrial DNA sequences and polymorphic microsatellites to examine the genetic divergence and genetic diversity of farmed and feral American mink populations. Our results suggest that there is admixture of individuals of different genetic characteristics between farmed and feral populations of mink. Furthermore, the genetic diversity of both farmed and feral American mink populations was high, and no bottleneck or population expansion was detected in most of the populations. These findings not only highlight the genetic characteristics of American mink in northeastern China but also contribute to the general understanding of the invasiveness of farmed species.
Background
Changes in population heterozygosity and genetic diversity play important roles in mediating life history traits of organisms; these changes often lead to phenotypic evolution in offspring, which become superior to their parents. In the present study, we examined phenotypic differentiation, the intestinal microbiome composition, and metabolism shift in the oriental fruit fly (Bactrocera dorsalis) by comparing an inbred (monophyletic) original population and an outbred (mixed) invasive population.
Results
The results showed that the outbred population of B. dorsalis had significantly higher biomass, adult longevity, and fecundity than the inbred population. Additionally, intestinal microflora analysis revealed that both Diutina rugosa and Komagataeibacter saccharivorans were significantly enriched in the outbred population with higher genetic heterozygosity. D. rugosa enrichment altered amino acid metabolism in the intestinal tract, and supplementing essential amino acids (e.g. histidine and glutamine) in the diet led to an increase in pupal weight of the outbred population. Additionally, transcriptome analysis revealed that the HSPA1S gene was significantly downregulated in the outbred population. HSPA1S was involved in activation of the JNK-MAPK pathway through negative regulation, caused the upregulation of juvenile hormone (JH), and led to an increase in biomass in the outbred flies.
Conclusion
In conclusion, the outbred population had an altered intestinal microbe composition, mediating metabolism and transcriptional regulation, leading to phenotypic differentiation; this may be a potential mechanism driving the global invasion of B. dorsalis. Thus, multiple introductions could lead to invasiveness enhancement in B. dorsalis through population mixing, providing preliminary evidence that changes in the intestinal microbiome can promote biological invasion.
1rGLpfiTdGk3QvEMFY5kHbVideo Abstract
Tragopogon (Asteraceae) includes two recently and repeatedly formed allopolyploids, T. mirus and T. miscellus, both of which formed in western North America following the human-mediated introduction of three diploids from Europe: T. dubius, T. porrifolius, and T. pratensis. We recently investigated the genetics of the introduction history to North America of T. dubius, the shared parent of both allopolyploids. Here, we investigate the introduction of T. pratensis into North America, the second diploid parent of T. miscellus. Using ITS sequence data, we found that T. pratensis as currently defined in the narrow sense is polyphyletic and comprises at least four different major ITS types in its native range. Of these native range ITS patterns, two have been introduced from Europe into North America and now occur widely across Canada and the U.S.A. Although the allotetraploid T. miscellus formed multiple times in western North America, only one of these ITS types was involved in the recurrent formations. These results for T. pratensis parallel our findings for T. dubius and further suggest that not all genotypes of these two species may be able to participate in the formation of allopolyploids. Our phylogenetic analyses reveal that several entities traditionally considered part of T. pratensis in the narrow sense are genetically distinct and mark unique lineages that may ultimately merit recognition as separate species. This proclivity for genetically distinct entities (potential cryptic species) within species recognized based on morphology appears common in Tragopogon. To unravel the complexities of what is referred to as “T. pratensis”, more intensive phylogenetic analyses involving many more samples from across the geographic range of the species are required, as are detailed assessments of taxonomy, morphology, and cytology.
Non-native lady beetle species have often been introduced, with variable success, into North America for biological control of aphids, scales, whiteflies, and other agricultural pests. Two predatory lady beetle species, Propylea quatuordecimpunctata and Hippodamia variegata, both originating from Eurasia, were first discovered near Montreal, Quebec, in North America in 1968 and 1984, respectively, and have since expanded into northeastern North America and the midwestern United States. In this study, we estimate the range-wide population structure, establishment and range-expansion, and recent evolutionary history of these species of non-native lady beetles using reduced representation genotyping-by-sequencing via ddRADseq. In addition, we quantified the responses to a key abiotic factor, photoperiod, that regulates adult reproductive diapause in these two species and may influence their latitudinal distribution and spread in North America. Our analyses detect (1) non-significant genetic differentiation and divergence among North American populations, (2) evidence of reduced contemporary gene flow within the continental US, (3) significant phenotypic differences in diapause induction despite genetic similarities across sampled populations.
Key Words: population genomics, invasive species, biological control, diapause
This datasheet on Melanoides tuberculata covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Further Information.
Les invasions biologiques constituent aujourd'hui une source d'inquiétude du fait de leur nette augmentation et des conséquences écologiques, économiques et sanitaires dont elles sont à l'origine. Pour qu'une population devienne envahissante, il faut (i) qu'elle soit introduite, (ii) qu'elle s'établisse et (iii) qu'elle prolifère. Chacune de ces trois étapes constitue un défi difficile à relever, et les processus en jeu sont encore mal connus. Cette thèse décrit un ensemble de recherches visant à comprendre l'invasion mondiale particulièrement réussie de la coccinelle asiatique Harmonia axyridis. Nous avons dans un premier temps étudié l'étape d'introduction en retraçant les routes d'invasion d'H. axyridis à l'aide de marqueurs microsatellites et de la méthode ABC (Approximate Bayesian Computation). Nous avons montré que la population envahissante la plus ancienne dans le nord-est américain avait été la tête de pont de l'invasion mondiale en devenant la source des foyers européen, sud-américain et africain. En Europe, on constate également une hybridation avec une souche de lutte biologique. Dans un deuxième temps, nous avons exploré l'étape d'établissement de l'espèce. Nous avons montré que les populations envahissantes d'H. axyridis avaient subi une purge génétique réduisant considérablement les effets associés à la dépression de consanguinité. Par ailleurs, l'événement d'hybridation en Europe apporte des avantages phénotypiques probables à cette population envahissante. Nous avons ensuite étudié plusieurs aspects de l'étape de prolifération. Nous avons montré que les populations européennes avaient évolué vers de plus fortes capacités de dispersion sur le front d'invasion. Par ailleurs, nos résultats montrent que la commercialisation en France d'une souche non-volante de lutte biologique a pu avoir des conséquences positives sur l'expansion de la population envahissante par des phénomènes d'hétérosis ou d'augmentation de variance génétique. Enfin, nous discutons de l'importance d'étudier de manière approfondie une espèce modèle telle qu'H. axyridis pour améliorer nos connaissances générales sur les mécanismes éco-évolutifs impliqués lors des invasions biologiques.
St Lucia is the world's oldest protected estuary and Africa's largest estuarine system. It is also the centerpiece of South Africa's first UNESCO World Heritage Site, the iSimangaliso Wetland Park, and has been a Ramsar Wetland of International Importance since 1986. Knowledge of its biodiversity, geological origins, hydrology, hydrodynamics and the long history of management is unique in the world. However, the impact of global change has culminated in unprecedented challenges for the conservation and management of the St Lucia system, leading to the recent initiation of a project in support of its rehabilitation and long-term sustainability. This timely volume provides a unique source of information on the functioning and management of the estuary for researchers, students and environmental managers. The insights and experiences described build on over 60 years of study and management at the site and will serve as a valuable model for similar estuaries around the world.
Biological introductions are unintended "natural experiments" that provide unique insights into evolutionary processes. Invasive phytophagous insects are of particular interest to evolutionary biologists studying adaptation, as introductions often require rapid adaptation to novel host plants. However, adaptive potential of invasive populations may be limited by reduced genetic diversity—a problem known as the "genetic paradox of invasions". One potential solution to this paradox is if there are multiple invasive waves that bolster genetic variation in invasive populations. Evaluating this hypothesis requires characterizing genetic variation and population structure in the introduced range. To this end, we assemble a reference genome and describe patterns of genetic variation in the introduced white pine sawfly, Diprion similis . This species was introduced to North America in 1914, where it has undergone a rapid host shift to the thin-needled eastern white pine ( Pinus strobus ), making it an ideal invasion system for studying adaptation to novel environments. To evaluate evidence of multiple introductions, we generated whole-genome resequencing data for 64 D. similis females sampled across the North American range. Both model-based and model-free clustering analyses supported a single population for North American D. similis . Within this population, we found evidence of isolation-by-distance and a pattern of declining heterozygosity with distance from the hypothesized introduction site. Together, these results support a single-introduction event. We consider implications of these findings for the genetic paradox of invasion and discuss priorities for future research in D. similis , a promising model system for invasion biology.
Tragopogon (Asteraceae) is an evolutionary model for the study of whole‐genome duplication, with two recently and repeatedly formed allopolyploids, T. mirus and T. miscellus, and many additional polyploid species. Tragopogon mirus and T. miscellus formed in western North America following the introduction of three diploids from Europe: T. dubius, T. porrifolius, and T. pratensis. Of these diploids, T. dubius is a shared parent of both tetraploids and is broadly defined and widely distributed in Eurasia. Because human‐mediated intercontinental introductions may lead to hybridization with local species, and associated polyploidization, the introduction history of T. dubius from Europe to North America provides further opportunity to investigate both the extent and consequences of plant introductions. Using ITS sequence data, we show that the morphologically diverse, broadly defined T. dubius comprises a complex of at least 10 different ITS types in its native range, six of which have been introduced from Europe into North America. Significantly, although the two allotetraploid species have each formed multiple times on geographical scales from local to regional, recurrent formation is the result of repeated hybridization involving only one of these ITS subtypes. These results reinforce earlier data suggesting that not all diploid genotypes can form allopolyploids. Several entities traditionally considered part of T. dubius s.l. are now recognized as distinct species (e.g., T. lainzii), and it is likely that other distinct ITS genotypes identified here may also mark unique lineages that ultimately merit recognition as separate species. However, more intensive phylogenetic analyses involving many more samples from across the geographic range of T. dubius are required, as are detailed assessments of taxonomy, morphology, and cytology.
Tall fleabane [ Conyza sumatrensis (Retz.) E. Walker] is commonly invasive in agricultural fields, reducing yield in various infested crops. The current study investigates the genetic diversity within and between a significant number of invasive C. sumatrensis biotypes in soybean fields in southern, southeastern and midwestern Brazil, using microsatellites as molecular markers. High and low observed and expected heterozygosity estimated in microsatellite loci supported our hypothesis that different levels of genetic diversity may be detected within biotypes from different invaded fields. Analysis of a significant number of biotypes in several fields showed high and low genetic diversity not associated with the geographic distribution, bottleneck effect and susceptibility to glyphosate. A deficit of heterozygous plants, high genetic divergence and moderate allele transference were also observed. Allele fixation was different in the different biotypes. The bottleneck effect was seen in biotypes with reduced genetic diversity and in biotypes with highest genetic diversity. Data on genetic diversity, bottleneck effect, and glyphosate resistance showed contrasts in biotypes from nearby invaded fields. Our study showed different genetic diversity levels in biotypes from invaded areas under the same climatic conditions.
Invasive species represent one of the foremost risks to global biodiversity. Here, we use population genomics to evaluate the history and consequences of an invasion of wild tomato- Solanum pimpinellifolium -onto the Galápagos islands from continental South America. Using >300 archipelago and mainland collections, we infer this invasion was recent and largely the result of a single event from central Ecuador. Patterns of ancestry within the genomes of invasive plants also reveal post-colonization hybridization and introgression between S. pimpinellifolium and the closely related Galapagos endemic Solanum cheesmaniae . Of admixed invasive individuals, those that carry endemic alleles at one of two different carotenoid biosynthesis loci also have orange fruits-characteristic of the endemic species-instead of typical red S. pimpinellifolium fruits. We infer that introgression of two independent fruit color loci explains this observed trait convergence, suggesting that selection has favored repeated transitions of red to orange fruits on the Galapagos.
One way to summarize the evolutionary dynamics of species introductions is to estimate how levels of genetic diversity in non-native populations are dif- ferent from those of their source populations. While it is typically assumed that a significant loss of diversity will be associated with species introduc- tions, the actual effect may be more complex, depending on propagule pressure and patterns of diversity and population structure in the native range of a species. We review a number of studies of animal species introductions in which allelic diversity and heterozygosity in the non-native and source ranges of each species can be compared, and find that the typical loss of diversity is minimal. The generality of this pattern may provide new insight into debates over the prevalence of stochastic processes in generating novel phenotypes or coadapted gene complexes in founder populations. These results suggest that the response of founder populations to natural selection in a novel environ- ment is generally more important than the stochastic effects of the founder event itself in determining the evolutionary trajectory of a population.
The distribution of variability was studied at various geographical scales in the tropical freshwater snail Melanoides tuberculata, in order to analyse the role of factors shaping this distribution, including the mating system and population dynamics. This parthenogenetic polyploid species reproduces mainly asexually, with males occurring at low frequency. About 800 individuals (38 sites) were sampled from Africa and the Middle East, where the species originated, and from recently colonized habitats in South and Central America, and especially the island of Martinique. We first described variation of general aspects and ornamentation of the shells. This analysis confirms the existence of discrete morphs. Second, individuals were studied at three microsatellite loci, showing that each morph is a genetic clone with some minor variation compatible with models of microsatellite evolution. The genetic analysis also showed much more variation within than between clones. However, two populations from Africa exhibited a large amount of variability, and a mixture of sexual and asexual reproduction might explain these genetic patterns. The worldwide distribution of variability is, therefore, compatible with the African origin of the species, and the introduction of a few clones in other parts of the world. These results also suggest that the distribution of variability in Martinique is influenced by flooding events, and that two morphs from Martinique can be interpreted as hybrids between two pre-existing morphs, based on morphological, genetic and geographical arguments.
Conservation biology needs to be concerned not just with exogenous threats to populations, but also with the changing nature
of populations themselves. In a previous review paper, we highlighted evolution in contemporary time (years to decades) as
a largely overlooked aspect of population responses to environmental perturbations. We argued that these responses might affect
the fate of natural, managed and exotic populations. In the present review, we discuss issues that may limit the integration
of contemporary evolution into conservation biology—with the intent that recognition of these limitations may foster research,
discussion and resolution. In particular, we consider (1) alternative perceptions of “evolutionary” and “ecological” time,
(2) the role of contemporary evolution as an ecological process, (3) fitness as a bridge between evolution and conservation,
and (4) challenges faced by conservation strategies based on gene flow estimation or manipulation. We close by highlighting
some situations in which current conservation approaches and contemporary evolution may require reconciliation.
Species invasions provide numerous unplanned and frequently, but imperfectly, replicated experiments that can be used to better understand the natural world. Classic studies by Darwin, Grinnell, Elton and others on these species-invasion experiments provided invaluable insights for ecology and evolutionary biology. Recent studies of invasions have resulted in additional insights, six of which we discuss here; these insights highlight the utility of using exotic species as ‘model organisms’. We also discuss a nascent hypothesis that might provide a more general, predictive understanding of invasions and community assembly. Finally, we emphasize how the study of invasions can help to inform our understanding of applied problems, such as extinction, ecosystem function and the response of species to climate change.
Human activities are not random in their negative and positive impacts on biotas. Emerging evidence shows that most species are declining as a result of human activities (‘losers’) and are being replaced by a much smaller number of expanding species that thrive in human-altered environments (‘winners’). The result will be a more homogenized biosphere with lower diversity at regional and global scales. Recent data also indicate that the many losers and few winners tend to be non-randomly distributed among higher taxa and ecological groups, enhancing homogenization.
Invasive species that penetrate habitat boundaries are likely to experience strong selection and rapid evolution. This study documents evolutionary shifts in tolerance and performance following the invasion of fresh water by the predominantly estuarine and salt marsh copepod Eurytemora affinis. Common-garden experiments were performed on freshwater-invading (Lake Michigan) and ancestral saline (St. Lawrence marsh) populations to measure shifts in adult survival (at 0, 5, and 25 PSU), and survival during development and development time (both using full-sib clutches split across 0, 5, 15, and 25 PSU). Results showed clear evidence of heritable shifts in tolerance and performance associated with freshwater invasions. The freshwater population exhibited a gain in low-salinity tolerance and a reduction in high-salinity tolerance relative to the saline population, suggesting tradeoffs. These tradeoffs were supported by negative genetic correlations between survival at fresh (0 PSU) versus higher salinities. Mortality in response to salinity occurred primarily before metamorphosis, suggesting that selection in response to salinity had acted primarily on the early life-history stages. The freshwater population exhibited curious patterns of life-history evolution across salinities, relative to the saline population, of retarded development to metamorphosis but accelerated development from metamorphosis to adulthood. This pattern might reflect tradeoffs between development rate and survival in fresh water at the early life-history stages, but some other selective force acting on later life-history stages. Significant effects of clutch (genotype) and clutch-by-salinity interaction (G × E) on survival and development time in both populations indicated ample genetic variation as substrate for natural selection. Variation for high-salinity tolerance was present in the freshwater population despite negative genetic correlations between high- and low-salinity tolerance. Results implicate the importance of natural selection and document the evolution of reaction norms during freshwater invasions.
There are two distinct reasons for making comparisons of genetic variation for quantitative characters. The first is to compare evolvabilities, or ability to respond to selection, and the second is to make inferences about the forces that maintain genetic variability. Measures of variation that are standardized by the trait mean, such as the additive genetic coefficient of variation, are appropriate for both purposes. Variation has usually been compared as narrow sense heritabilities, but this is almost always an inappropriate comparative measure of evolvability and variability. Coefficients of variation were calculated from 842 estimates of trait means, variances and heritabilities in the literature. Traits closely related to fitness have higher additive genetic and nongenetic variability by the coefficient of variation criterion than characters under weak selection. This is the reverse of the accepted conclusion based on comparisons of heritability. The low heritability of fitness components is best explained by their high residual variation. The high additive genetic and residual variability of fitness traits might be explained by the great number of genetic and environmental events they are affected by, or by a lack of stabilizing selection to reduce their phenotypic variance. Over one-third of the quantitative genetics papers reviewed did not report trait means or variances. Researchers should always report these statistics, so that measures of variation appropriate to a variety of situations may be calculated.
Eight alien freshwater snail species were introduced into Martinique Island during the last 50 years. The introduced snails include four planorbids (Biomphalaria straminea, Helisoma duryi, Amerianna carinata and Gyraulus sp.), three thiarids (Melanoides tuberculata, M. amabilis and Tarebia granifera) and one ampullarid (Marisa cornuarietis). Four of these species rapidly colonized the whole Martinican hydrographic system whereas the other four remained restricted to some particular sites. The invasion processes were documented during the last 20 years and showed (i) a rapid invasion of the island by several morphs of M. tuberculata at the beginning of the 80's; (ii) the introduction of T. granifera in 1991 and M. amabilis in 1997; and (iii) the rapid spread of these last two species throughout the island. In the years following its introduction, M. tuberculata was used in biological control experiments against the snail hosts of schistosomiasis, B. glabrata and B. straminea. Experiments were conducted with success in several groups of water-cress beds which constituted the latest transmission sites for schistosomiasis at the beginning of the 80's. A malacological survey carried out in 2000 all over the island showed the absence of B. glabrata but the presence of some residual populations of B. straminea. Long-term studies carried out in Martinique have shown that the thiarids are able to maintain relatively stable populations over a long period of time, thus preventing recolonization by the snail hosts. Within this context the invasion of the hydrographic system of Martinique by thiarid snails has resulted in an efficient and sustainable control of the intermediate hosts of schistosomiasis.
A genetic paradox exists in invasion biology: how do introduced populations, whose genetic variation has probably been depleted by population bottlenecks, persist and adapt to new conditions? Lessons from conservation genetics show that reduced genetic variation due to genetic drift and founder effects limits the ability of a population to adapt, and small population size increases the risk of extinction. Nonetheless, many introduced species experiencing these same conditions during initial introductions persist, expand their ranges, evolve rapidly and become invasive. To address this issue, we studied the brown anole, a worldwide invasive lizard. Genetic analyses indicate that at least eight introductions have occurred in Florida from across this lizard's native range, blending genetic variation from different geographic source populations and producing populations that contain substantially more, not less, genetic variation than native populations. Moreover, recently introduced brown anole populations around the world originate from Florida, and some have maintained these elevated levels of genetic variation. Here we show that one key to invasion success may be the occurrence of multiple introductions that transform among-population variation in native ranges to within-population variation in introduced areas. Furthermore, these genetically variable populations may be particularly potent sources for introductions elsewhere. The growing problem of invasive species introductions brings considerable economic and biological costs. If these costs are to be mitigated, a greater understanding of the causes, progression and consequences of biological invasions is needed.
Why sex evolved and persists is a problem for evolutionary biology, because sex disrupts favourable gene combinations and requires an expenditure of time and energy. Further, in organisms with unequal-sized gametes, the female transmits her genes at only half the rate of an asexual equivalent (the twofold cost of sex). Many modern theories that provide an explanation for the advantage of sex incorporate an idea originally proposed by Weismann more than 100 years ago: sex allows natural selection to proceed more effectively because it increases genetic variation. Here we test this hypothesis, which still lacks robust empirical support, with the use of experiments on yeast populations. Capitalizing on recent advances in the molecular biology of recombination in yeast, we produced by genetic manipulation strains that differed only in their capacity for sexual reproduction. We show that, as predicted by the theory, sex increases the rate of adaptation to a new harsh environment but has no measurable effect on fitness in a new benign environment where there is little selection.
Plant invasions often involve rapid evolutionary change. Founder effects, hybridization, and adaptation to novel environments cause genetic differentiation between native and introduced populations and may contribute to the success of invaders. An influential idea in this context has been the Evolution of Increased Competitive Ability (EICA) hypothesis. It proposes that after enemy release plants rapidly evolve to be less defended but more competitive, thereby increasing plant vigour in introduced populations. To detect evolutionary change in invaders, comparative studies of native versus introduced populations are needed. Here, we review the current empirical evidence from: (1) comparisons of phenotypic variation in natural populations; (2) comparisons of molecular variation with neutral genetic markers; (3) comparisons of quantitative genetic variation in a common environment; and (4) comparisons of phenotypic plasticity across different environments. Field data suggest that increased vigour and reduced herbivory are common in introduced plant populations. In molecular studies, the genetic diversity of introduced populations was not consistently different from that of native populations. Multiple introductions of invasive plants appear to be the rule rather than the exception. In tests of the EICA hypothesis in a common environment, several found increased growth or decreased resistance in introduced populations. However, few provided a full test of the EICA hypothesis by addressing growth and defence in the same species. Overall, there is reasonable empirical evidence to suggest that genetic differentiation through rapid evolutionary change is important in plant invasions. We discuss conceptual and methodological issues associated with cross-continental comparisons and make recommendations for future research. When testing for EICA, greater emphasis should be put on competitive ability and plant tolerance. Moreover, it is important to address evolutionary change in characteristics other than defence and growth that could play a role in plant invasions.
Despite the increasing biological and economic impacts of invasive species, little is known about the evolutionary mechanisms that favor geographic range expansion and evolution of invasiveness in introduced species. Here, we focus on the invasive wetland grass Phalaris arundinacea L. and document the evolutionary consequences that resulted from multiple and uncontrolled introductions into North America of genetic material native to different European regions. Continental-scale genetic variation occurring in reed canarygrass' European range has been reshuffled and recombined within North American introduced populations, giving rise to a number of novel genotypes. This process alleviated genetic bottlenecks throughout reed canarygrass' introduced range, including in peripheral populations, where depletion of genetic diversity is expected and is observed in the native range. Moreover, reed canarygrass had higher genetic diversity and heritable phenotypic variation in its invasive range relative to its native range. The resulting high evolutionary potential of invasive populations allowed for rapid selection of genotypes with higher vegetative colonization ability and phenotypic plasticity. Our results show that repeated introductions of a single species may inadvertently create harmful invaders with high adaptive potential. Such invasive species may be able to evolve in response to changing climate, allowing them to have increasing impact on native communities and ecosystems in the future. More generally, multiple immigration events may thus trigger future adaptation and geographic spread of a species population by preventing genetic bottlenecks and generating genetic novelties through recombination.
• biological invasion
• genotypic diversity
• multiple immigration
• range expansion
• phenotypic plasticity
There is mounting evidence that reduced genetic diversity in invasive populations is not as commonplace as expected. Recent studies indicate that high propagule vectors, such as ballast water and shellfish transplantations, and multiple introductions contribute to the elimination of founder effects in the majority of successful aquatic invasions. Multiple introductions, in particular, can promote range expansion of introduced populations through both genetic and demographic mechanisms. Closely related to vectors and corridors of introduction, propagule pressure can play an important role in determining the genetic outcome of introduction events. Even low-diversity introductions have numerous means of avoiding the negative impact of diversity loss. The interaction of high propagule vectors and multiple introductions reveal important patterns associated with invasion success and deserve closer scrutiny.
In Martinique the freshwater snail Melanoides tuberculata was discovered for the first time in 1979. Rapid colonization of the whole island was documented. Three distinct morphs were recognized by conchological characteristics. The change of the snail densities and the frequency of these three morphs showed the decline of one morph following the introduction of the two others. -from Authors
This study describes the biology and reproduction of several isolated populations of Melanoides tuberculoid found in various water bodies in Israel and the Sinai Peninsula. Although these snails are described as parthenogenetic, we find that some populations in Israel contain 20–33% of males producing motile spermia, while other populations consist only of females. In all populations the offspring are incubated in brood-pouches. The length of incubation is correlated to population density. Electrophoretic studies of esterase (two loci) and acid phosphatase isozymes show that the observed distribution of genotypes within some of the snail populations are in good agreement with the Hardy-Weinberg expectation. As offspring of single females bear proteins not found in the mothers, we conclude that fertilization occurs within the population.
The literature on biological invasions has principally focused on understanding the ecological controls and consequences of invasions. Invading populations, however, often experience rapid evolutionary changes associated with or soon after their introduction. Ecological and evolutionary processes can, therefore, potentially interact over relatively short timescales. A number of recent studies have begun to document these interactions and their effect on short-term invasion dynamics: (1) The degree to which founder effects, drift, and inbreeding alter the genetic composition of introduced populations is mediated by migration and dispersal patterns, the population dynamics of founding populations, and life history. The genetic changes associated with founding can themselves feed back on population dynamics and life history. (2) Patterns of human-mediated dispersal and landscape change can influence the frequency and pattern of hybridization, which in turn can alter invasion dynamics. These altered invasion dynamics can influence the frequency and pattern of subsequent hybridization and introgression. (3) Strong selection can rapidly generate ecotypic specialization. Dispersal patterns, founder effects, genetic system, and life history influence the rate of local adaptation, its persistence, and its distribution in a landscape. (4) Introduced populations are subject to selection on life history traits and can serve as selective pressure on the life history traits of native populations. Life history evolution in both natives and aliens can influence ecological interactions and population dynamics, which in turn can influence the evolution of life history. Too few studies have investigated these interactions to definitively assess their overall generality or to determine how the relative interaction strength of ecology and evolution varies across taxa or ecosystems. However, the studies that do exist report interactions from a wide breadth of taxa and from all stages in the invasion process. This suggests that ecological-evolutionary interactions may have a more pervasive influence on contemporary invasion dynamics than previously appreciated, and that at least in some situations an explicit understanding of the contemporary co-influence of ecology and evolution can produce more effective and predictive control strategies.
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The application of an extended form of von Bertalanffy's growth function to plant data is considered; the equation has considerable
flexibility, but is used only to supply an empirical fit. In order to aid the biological analysis of such growth data as are
capable of representation by the function, general rate parameters are deduced which are related in a simple manner to its
constants.
Aims To test the magnitude and direction of the effects of large‐scale environmental factors (latitude and habitat type: lotic or lentic) on the intraspecific variations in multiple life‐history traits, across multiple European freshwater fish species. To test the relevance of defining species traits by quantifying the magnitude of interspecific vs. intraspecific variability in traits.
Location Europe.
Methods We obtained estimates of 11 fish traits from published sources for 1089 populations of 25 European freshwater fish species. Traits were: longevity, maximal length, growth rate, asymptotic length, mortality rate, age and length at maturation, fecundity, egg size, gonadosomatic index, and length of breeding season. We described population habitats by latitude and habitat type (lotic or lentic), when available. For each species we tested the combined effect of latitude and habitat type on the intraspecific variation of each trait using analysis of covariance ( ancova ). We compared the intraspecific variation in traits with the variation between species using an analysis of variance ( anova ) for each trait, all species pooled.
Results We found a consistent effect in direction of latitude on six traits, but we showed that this effect is not always significant across species. Higher‐latitude populations often grew more slowly, matured later, had a longer life span and a higher maximal and asymptotic length, and allocated more energy to reproduction than populations at lower latitudes. By contrast, we noted only a slight effect of habitat type on the intraspecific variation in traits, except for Salmo trutta . All traits varied significantly between species. However, traits such as growth rate, mortality rate and length of breeding season varied more between populations than between species, whereas fecundity and traits associated with body length varied more between species.
Main conclusions Latitude, in contrast to habitat type, is an important factor influencing several traits of geographically widely dispersed populations of multiple European freshwater fish species. Species traits that vary more between species than between populations are attractive variables for understanding and predicting the responses of stream fish communities to their environment.
Recent research has revealed that evolution often occurs on contemporary timescales, often within decades. Contemporary evolution is associated with the same factors that are driving the current extinction crisis: habitat loss and degradation, overharvesting and exotic species. Thus, it is relevant to many conservation situations. First, habitat fragmentation might influence the potential of a population to adapt in response environmental degradation. Second, certain harvesting strategies can result in the evolution of life-history traits, ultimately resulting in negative impacts on harvestable yield. Third, the establishment of exotic species can be influenced by their adaptive potential and our ability to limit that potential. Furthermore, contemporary evolution is of concern for intensively managed species, because it might reduce their fitness in native habitats. Ultimately, contemporary evolution is influenced by complex interactions among population size, genetic variation, the strength of selection, and gene flow, making most management scenarios unique. In a world filled with contemporary evolution, conservation efforts that ignore its implications will be less efficient and perhaps even risk prone.
The present paper discusses the spread of freshwater snails that act as intermediate hosts for various trematodes that cause diseases in man and in cattle. Examples of snail species which have spread across natural barriers are reviewed as well as the mechanisms involved in this transport. Focus is put on the extensive trade in freshwater aquatic plants and aquarium fish, and the need for better control of this trade is emphasized in order to minimize the risk of unintended import of potentially harmful snails.
The introduction and rapid spread of Drosophila subobscura in the New World two decades ago provide an opportunity to determine the predictability and rate of evolution of a geographic
cline. In ancestral Old World populations, wing length increases clinally with latitude. In North American populations, no
wing length cline was detected one decade after the introduction. After two decades, however, a cline has evolved and largely
converged on the ancestral cline. The rate of morphological evolution on a continental scale is very fast, relative even to
rates measured within local populations. Nevertheless, different wing sections dominate the New versus Old World clines. Thus,
the evolution of geographic variation in wing length has been predictable, but the means by which the cline is achieved is
contingent.
The parthenogenetic snail Melanoides tuberculata, present in tropical fresh waters of most of the Old World before 1950, has now invaded the Neotropical area. The phylogeography of this snail was studied to evaluate the pathways and number of such invasions. Because of parthenogenetic reproduction, individuals are structured into genetical clones. Within populations from both the original and invaded areas, several morphologically distinct clones (referred to as morphs) often coexist but the amount of genetic divergence among morphs is unknown. Individuals from 27 morphs and 40 populations world-wide were sequenced at two mitochondrial genes (12S and 16S). Our phylogenetic reconstruction suggests that (i) most of the morphological variation observed in the New World predates invasion, (ii) at least six independent introductions have occurred, and (iii) invasive clones are found throughout most of the phylogenetic tree and do not come from a particular region of the area of origin. Two ideas are discussed in the light of these results. The first lies with the specificities of parthenogenesis in an invasion context. While in sexual species, independently introduced populations eventually merge into a single invasive population, in a parthenogenetic species independently introduced clones have distinct invasion dynamics and possibly exclude each other. Second, although repeated invasions in Melanoides may have an impact on indigenous molluscan faunas, their most likely effect is the world-wide homogenization of the invasive taxon itself.
Understanding the capacity of natural populations to adapt to their local environment is a central topic in evolutionary biology. Phenotypic differences between populations may have a genetic basis, but showing that they reflect different adaptive optima requires the quantification of both gene flow and selection. Good empirical data are rare. Using data on a spatially structured island population of great tits (Parus major), we show here that a persistent difference in mean clutch size between two subpopulations only a few kilometres apart has a major genetic component. We also show that immigrants from outside the island carry genes for large clutches. But gene flow into one subpopulation is low, as a result of a low immigration rate together with strong selection against immigrant genes. This has allowed for adaptation to the island environment and the maintenance of small clutches. In the other area, however, higher gene flow prevents local adaptation and maintains larger clutches. We show that the observed small-scale genetic difference in clutch size is not due to divergent selection on the island, but to different levels of gene flow from outside the island. Our findings illustrate the large effect of immigration on the evolution of local adaptations and on genetic population structure.
Many invasive taxa are hybrids, but how hybridization boosts the invasive process remains poorly known. We address this question in the clonal freshwater snail Melanoides tuberculata from Martinique, using three parental and two hybrid lines. We combine an extensive field survey (1990-2003) and a quantitative genetic experiment to show that hybrid lines have outcompeted their parents in natural habitats, and that this increased invasiveness co-occurred with pronounced shifts in life-history traits, such as growth, fecundity and juvenile size. Given the little time between hybrid creation and sampling, and the moderate standing genetic variance for life-history traits in hybrids, we show that some of the observed trait changes between parents and hybrids were unlikely to arise only by continuous selection. We therefore suggest that a large part of hybrid advantage stems from immediate heterosis upon hybridization.
Exotic species invasions create almost ideal conditions for promoting evolutionary diversification: establishment of allopatric populations in new environmental conditions; altered ecological opportunities for native species; and new opportunities for hybridization between previously allopatric taxa. Here, we review recent studies of the evolutionary consequences of species invasions, revealing abundant and widespread examples of exotic species promoting evolutionary diversification via increased genetic differentiation among populations of both exotic and native species and the creation of new hybrid lineages. Our review indicates that, although the well-documented reductions to biodiversity caused by exotic species might outweigh the increases resulting from diversification, a complete understanding of the net effects of exotic species on biodiversity in the long term will require consideration of both.
Invasive species are predicted to suffer from reductions in genetic diversity during founding events, reducing adaptive potential. Integrating evidence from two literature reviews and two case studies, we address the following questions: How much genetic diversity is lost in invasions? Do multiple introductions ameliorate this loss? Is there evidence for loss of diversity in quantitative traits? Do invaders that have experienced strong bottlenecks show adaptive evolution? How do multiple introductions influence adaptation on a landscape scale? We reviewed studies of 80 species of animals, plants, and fungi that quantified nuclear molecular diversity within introduced and source populations. Overall, there were significant losses of both allelic richness and heterozygosity in introduced populations, and large gains in diversity were rare. Evidence for multiple introductions was associated with increased diversity, and allelic variation appeared to increase over long timescales (~100 years), suggesting a role for gene flow in augmenting diversity over the long-term. We then reviewed the literature on quantitative trait diversity and found that broad-sense variation rarely declines in introductions, but direct comparisons of additive variance were lacking. Our studies of Hypericum canariense invasions illustrate how populations with diminished diversity may still evolve rapidly. Given the prevalence of genetic bottlenecks in successful invading populations and the potential for adaptive evolution in quantitative traits, we suggest that the disadvantages associated with founding events may have been overstated. However, our work on the successful invader Verbascum thapsus illustrates how multiple introductions may take time to commingle, instead persisting as a 'mosaic of maladaptation' where traits are not distributed in a pattern consistent with adaptation. We conclude that management limiting gene flow among introduced populations may reduce adaptive potential but is unlikely to prevent expansion or the evolution of novel invasive behaviour.
Acknowledgments We thank B. Delay and S. Samadi for assistance in the field; we are also grateful to the many persons who sent us samples of Melanoides tubercu-lata and to Ronce for critically reading the manuscript. This work was funded by grants from the French ministry of Environment
- A Estoup
- J Foucaud
- M Kirkpatrick
- T Lenormand
- I Olivieri
- V Ravigné
Supplemental Data One figure and five tables are available at http://www.current-biology.com/ cgi/content/full/18/5/363/DC1/. Acknowledgments We thank B. Delay and S. Samadi for assistance in the field; we are also grateful to the many persons who sent us samples of Melanoides tubercu-lata and to A. Estoup, J. Foucaud, M. Kirkpatrick, T. Lenormand, I. Olivieri, V. Ravigné, and O. Ronce for critically reading the manuscript. This work was funded by grants from the French ministry of Environment (MEDD, ECOFOR, and INVABIO programs).
This analysis also was used to test specific contrasts between both CPF and FDF and all other morphs. A genetic variance-covariance ma-trix was generated in each morph by using a MANOVA with family as factor
- Table
- S
Table S3). This analysis also was used to test specific contrasts between both CPF and FDF and all other morphs. A genetic variance-covariance ma-trix was generated in each morph by using a MANOVA with family as factor [28]. These variances and covariances were used to represent the distribu-tions of genotypic values as 90% ellipses (Figure 3B).
Contemporary evolution meets conservation biology
- Stockwell
Mechanisms that drive evolutionary change
- Wares