[Show abstract][Hide abstract] ABSTRACT: Invasion success may be expected to increase with residence time (i.e., time since first introduction) and secondary releases (i.e., those that follow the original introduction), but this has rarely been tested in natural fish populations. We compared genetic and phenotypic divergence in rainbow trout and brown trout in Chile and the Falkland Islands to test the prediction that adaptive divergence, measured as PST/FST, would increase with residence time and secondary releases. We also explored whether interspecific competition between invaders could drive phenotypic divergence. Residence time had no significant effect on genetic diversity, phenotypic divergence, effective population size, or signatures of expansion of invasive trout. In contrast, secondary releases had a major effect on trout invasions, and rainbow trout populations mostly affected by aquaculture escapees showed significant divergence from less affected populations. Coexistence with brown trout had a positive effect on phenotypic divergence of rainbow trout. Our results highlight an important role of secondary releases in shaping fish invasions, but do not support the contention that older invaders are more differentiated than younger ones. They also suggest that exotic trout may not have yet developed local adaptations in these recently invaded habitats, at least with respect to growth-related traits.
[Show abstract][Hide abstract] ABSTRACT: The relationship between invaders and the pathogens encountered in their new environment can have a large effect on invasion success. Invaders can become free from their natural pathogens and reallocate costly immune resources to growth and reproduction, thereby increasing invasion success. Release from enemies and relaxation of selective pressures could render newly founded populations more variable at immune-related genes, such as the major histocompatibility complex (MHC), particularly when they have different origins. Using rainbow and brown trout, two of the world's most successful fish invaders, we tested the general hypothesis that invaders should display high intrapopulation immunogenetic diversity and interpopulation divergence, due to the interplay between genetic drift and successive waves of genetically divergent introductions. We analysed genetic diversity and signatures of selection at the MHC class II β immune-related locus. In both species, MHC diversity (allelic richness and heterozygosity) for southern hemisphere populations was similar to values reported for populations at their native range. However, MHC functional diversity was limited, and population immunogenetic structuring weaker than that observed using neutral markers. Depleted MHC functional diversity could reflect a decrease in immune response, immune-related assortative mating or selection for resistance to newly encountered parasites. Given that the role of MHC diversity in the survival of these populations remains unclear, depleted functional diversity of invasive salmonids could compromise their long-term persistence. A better understanding of the eco-immunology of invaders may help in managing and preventing the impact of biological invasions, a major cause of loss of biodiversity worldwide.
[Show abstract][Hide abstract] ABSTRACT: The ability of invasive species to adapt to novel conditions depends on population size and environmental mismatch, but also on genetic variation. Away from their native range, invasive species confronted with novel selective pressures may display different levels of neutral versus functional genetic variation. However, the majority of invasion studies have only examined genetic variation at neutral markers, which may reveal little about how invaders adapt to novel environments. Salmonids are good model systems to examine adaptation to novel pressures because they have been translocated all over the world and represent major threats to freshwater biodiversity in the Southern Hemisphere, where they have become invasive. We examined patterns of genetic differentiation at seven putatively neutral (microsatellites) loci and one immune-related major histocompatibility complex (MHC class II-β) locus among introduced rainbow trout living in captivity (farmed) or under natural conditions (naturalized) in Chilean Patagonia. A significant positive association was found between differentiation at neutral and functional markers, highlighting the role of neutral evolutionary forces in shaping genetic variation at immune-related genes in salmonids. However, functional (MHC) genetic diversity (but not microsatellite diversity) decreased with time spent in the wild since introduction, suggesting that there was selection against alleles associated with captive rearing of donor populations that do not provide an advantage in the wild. Thus, although high genetic diversity may initially enhance fitness in translocated populations, it does not necessarily reflect invasion success, as adaptation to novel conditions may result in rapid loss of functional MHC diversity.
Ecology and Evolution 09/2013; 3(10):3359-68. · 1.66 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The conservation of data deficient species is often hampered by inaccurate species delimitation. The galaxiid fishes Aplochiton zebra and Aplochiton taeniatus are endemic to Patagonia (and for A. zebra the Falkland Islands), where they are threatened by invasive salmonids. Conservation of Aplochiton is complicated because species identification is hampered by the presence of resident as well as migratory ecotypes that may confound morphological discrimination. We used DNA barcoding (COI, cytochrome b) and a new developed set of microsatellite markers to investigate the relationships between A. zebra and A. taeniatus and to assess their distributions and relative abundances in Chilean Patagonia and the Falkland Islands. Results from both DNA markers were 100% congruent and revealed that phenotypic misidentification was widespread, size-dependent, and highly asymmetric. While all the genetically classified A. zebra were correctly identified as such, 74% of A. taeniatus were incorrectly identified as A. zebra, the former species being more widespread than previously thought. Our results reveal, for the first time, the presence in sympatry of both species, not only in Chilean Patagonia, but also in the Falkland Islands, where A. taeniatus had not been previously described. We also found evidence of asymmetric hybridisation between female A. taeniatus and male A. zebra in areas where invasive salmonids have become widespread. Given the potential consequences that species misidentification and hybridisation can have for the conservation of these endangered species, we advocate the use of molecular markers in order to reduce epistemic uncertainty.
PLoS ONE 01/2012; 7(3):e32939. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 1. Direct ecological effects of biological invasions have been widely documented, but indirect genetic effects on native species are poorly known. In many cases this is due to lack of information on the genetic structure of species affected by invasions. 2. We used microsatellite DNA loci to estimate the genetic structure and gene flow patterns of Galaxias maculatus, a galaxiid fish endemic to the Southern Hemisphere which is increasingly being threatened by salmonid invasions. 3. Analysis of nine diadromous populations of G. maculatus in Chilean Patagonia (an area heavily impacted by farming of non-native salmonids) indicates that dispersal is mostly a passive process, seemingly driven by wind and currents, and resulting in high gene flow and weak population structuring. 4. Gene flow was asymmetrical, with three populations acting as sources and six populations acting as sinks. Sinks had lower habitat quality and had a greater incidence of adults than sources, which consisted mostly of juveniles. 5. Rivers invaded by salmonid escapees experienced significantly higher aquaculture pressure than rivers where salmonid escapees were apparently absent, but no effect on genetic diversity of G. maculatus could be detected.6. We discuss whether salmonid aquaculture might affect the demography and connectivity of galaxiid metapopulations: indirectly through habitat alteration and directly through escapes of predatory fish.
[Show abstract][Hide abstract] ABSTRACT: The brine shrimp Artemia is a micro-crustacean, well adapted to the harsh conditions that severely hypersaline environments impose on survival and reproduction. Adaptation to these conditions has taken place at different functional levels or domains, from the individual (molecular-cellular-physiological) to the population level. Such conditions are experienced by very few equivalent macro-planktonic organisms; thus, Artemia can be considered a model animal extremophile offering a unique suite of adaptations that are the focus of this review. The most obvious is a highly efficient osmoregulation system to withstand up to 10 times the salt concentration of ordinary seawater. Under extremely critical environmental conditions, for example when seasonal lakes dry-out, Artemia takes refuge by producing a highly resistant encysted gastrula embryo (cyst) capable of severe dehydration enabling an escape from population extinction. Cysts can be viewed as gene banks that store a genetic memory of historical population conditions. Their occurrence is due to the evolved ability of females to "perceive" forthcoming unstable environmental conditions expressed by their ability to switch reproductive mode, producing either cysts (oviparity) when environmental conditions become deleterious or free-swimming nauplii (ovoviviparity) that are able to maintain the population under suitable conditions. At the population level the trend is for conspecific populations to be fragmented into locally adapted populations, whereas species are restricted to salty lakes in particular regions (regional endemism). The Artemia model depicts adaptation as a complex response to critical life conditions, integrating and refining past and present experiences at all levels of organization. Although we consider an invertebrate restricted to a unique environment, the processes to be discussed are of general biological interest. Finally, we highlight the benefits of understanding the stress response of Artemia for the well-being of human populations.
[Show abstract][Hide abstract] ABSTRACT: Aquaculture is a major source of invasive aquatic species, despite the fact that cultured organisms often have low genetic diversity and tend to be maladapted to survive in the wild. Yet, to what extent aquaculture escapees become established by means of high propagule pressure and multiple origins is not clear. We analysed the genetic diversity of 15 established populations and four farmed stocks of non-native rainbow trout in Chile, a species first introduced for recreational fishing around 1900, but which has in recent decades escaped in large numbers from fish farms and become widespread. Aquaculture propagule pressure was a good predictor of the incidence of farm escapees, which represented 16% of all free-ranging rainbow trout and were present in 80% of the study rivers. Hybrids between farm escapes and established trout were present in all rivers at frequencies ranging between 7 and 69%, and population admixture was positively correlated with genetic diversity. We suggest that non-native salmonids introduced into the Southern Hemisphere could benefit from admixture because local adaptations may not have yet developed, and there may be initially little fitness loss resulting from outbreeding depression.
[Show abstract][Hide abstract] ABSTRACT: The Chilean saline lakes are distributed mainly in the Atacama desert in northern Chile and the southern Patagonian plains. The scarce studies are restricted mainly to northern Chilean saline lakes, and these revealed that the main component in these ecosystems are the halophylic copepod Boeckella poopoensis Marsh 1906, or the brine shrimp Artemia franciscana (Kellog, 1906), and both species do not coexist. The present study consisted of field observations in zooplankton assemblages in southern Chilean saline lakes (51-53 ºS). These first observations revealed three different patterns, one saline lake only with A. persimilis (Piccinelli and Prosdocimi, 1968), a second lake only with B. poopensis, and a third lake with A. persimilis, B. poopoensis and unidentified harpacticoid copepod. These results are different in comparison with the observations in the literature that described the non-coexistence between B. poopoensis with brine shrimps. Ecological and biogeographical topics were discussed.
Brazilian journal of biology = Revista brasleira de biologia 11/2010; 70(4):1031-2.
[Show abstract][Hide abstract] ABSTRACT: Zooplankton diversity in shallow salt lakes of the Andean countries in South America is low and distribution is highly dependent on salinity, which varies from moderate to high. At salinities lower than 90 g/l, the halophilic copepod Boeckella poopoensis (Marsh, 1906) predominates, whereas above that level the anostracan Artemia franciscana (Kellogg, 1912) is the exclusive component of the habitat. This constitutes, however, fragmentary information only. A review of the available literature for Andean saline lakes in Bolivia, Chile, and Peru, confirms that presence and distribution of both species is significantly driven by salinity levels. The results of a species co-occurrence null model analysis, indicates that species associations are not random, and these results are supported by the correlation analysis, which indicates a significant, inverse correlation between species number and salinity, and a significant direct relation of species number with surface of the habitat. The low species diversity characteristically seen in these habitats and their dependence on salinity changes effectuated by weather conditions, provide a good model-system for monitoring weather change. La diversidad del zooplankton en lagos salinos poco profundos de Sudamérica es baja y su distribución depende altamente de la salinidad, la cual varía de moderada a alta. A salinidades menores a 90 g/l predomina el copépodo halofílico Boeckella poopoensis (Marsh, 1906), mientras que a salinidades superiores a ese nivel, el anostraco Artemia franciscana (Kellogg, 1912) es el componente exclusivo de los hábitats. Esto constituye sin embargo una información parcial. En una revisión de la literatura disponible para lagos salinos Andinos en Bolivia, Chile y Perú se confirma que la presencia y distribución de ambas especies está significativamente regulada por el nivel de la salinidad. Los resultados del modelo nulo de co-ocurrencia de especies indican que las asociaciones de especies no son aleatorias, y estos resultados están respaldados por el análisis de correlación, el cual indica una relación inversa significativa entre número de especies con salinidad, y hubo relaciones directas significativas entre número de especies con la superficie del hábitat. El bajo número de especies que es característico de estos hábitats y su dependencia con los cambios de salinidad efectuado por las condiciones climáticas provee un buen modelo de sistema de monitoreo de cambios climáticos.
[Show abstract][Hide abstract] ABSTRACT: Rhizobacteria are capable of stimulating plant growth through a variety of mechanisms that include improvement of plant nutrition, production and regulation of phytohormones, and suppression of disease causing organisms. While considerable research has demonstrated their potential utility, the successful application of plant growth promoting rhizobacteria (PGPR) in the field has been limited by a lack of knowledge of ecological factors that determine their survival and activity in the plant rhizosphere. To be effective, PGPR must maintain a critical population density of active cells. Inoculation with PGPR strains can temporarily enhance the population size, but inoculants often have poor survival and compete with indigenous bacteria for available growth substrates. PGPR often present more than one mechanism for enhancing plant growth and experimental evidence suggests that the plant growth stimulation is the net result of multiple mechanisms of action that may be activated simultaneously. The aim of this review is to describe PGPR modes of action and discuss practical considerations for PGPR use in agriculture.
Journal of Soil Science and Plant Nutrition. 01/2010; 10(2):293–319.
[Show abstract][Hide abstract] ABSTRACT: The brine shrimp Artemia (Crustacea, Branchiopoda), a paradigmatic inhabitant of hypersaline lakes, has molecular features to survive under stressful conditions, such as the p26 heat shock protein. We report the RFLP fingerprinting pattern (four restriction enzymes) of a 217 bp fragment of exon2 of the Hsp26 gene in six Artemia franciscana and four Artemia persimilis populations, the most genetically divergent Artemia species co-occurring in latitudinal extremes of Chile. The species-specific RFLP pattern observed is a simple and cost-effective single-locus tool for species delimitation and experimental testing the habitat-induced isolation barrier between them.
[Show abstract][Hide abstract] ABSTRACT: Exotic salmonids were deliberately introduced to the Southern Hemisphere during the last part of the 20th century, initially to boost sport fishing and later to develop an aquaculture industry. Early introductions were justified by governments on purely utilitarian arguments as it was felt that translocated salmonids would capitalize on otherwise 'underutilized' aquatic niches. A century later, exotic salmonids are established in nearly all places where they were originally introduced and beyond, and constitute one of the main threats to endemic fish fauna, amongst which galaxiid fishes have perhaps been impacted the most. We screened the literature to document the changing perspectives on exotic salmonids in the Southern Hemisphere, and employed SWOT analysis to assess the conservation prognosis of native galaxiids in the face of salmonid invasions. Our analysis indicates that opinions differ - and contradictions abound - as to how to prevent further salmonid encroachment. This is largely due to lack of information on the impact of exotics but, more importantly, because the problem is often approached merely from a socio-economic perspective. Sport fishermen, for example, actively support the stocking of rivers to enhance sport fisheries and argue in favour of considering established salmonids as part of the native biodiversity, but also want to see an end to salmonids escaping from fish farms. The salmon industry tends to stress the social and economic benefits brought about by aquaculture, but continues to demand the right to expand and self-regulate. Governments, on the other hand, have not always had consistent or clear policies on exotic salmonids, and have tended to favour some stakeholders and penalized others. Our analysis emphasizes the need to consider biologically meaningful time scales when assessing impacts on biodiversity, and stresses the need to anticipate shifts in public opinion and stakeholder support in conservation.
Systematics and Biodiversity 01/2010; 8:447-459. · 1.88 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta are the world’s two most widespread exotic fishes, dominate the fish communities of most cold- temperate waters in the southern hemisphere and are implicated in the decline and extirpation of native fish species. Here, we provide the first direct comparison of the impacts of rainbow and brown trout on populations of a native fish by quantifying three components of exotic species impact: range, abundance and effect. We surveyed 54 small streams on the island of Chilo ´e in Chilean Patagonia and found that the rainbow trout has colonized significantly more streams and has a wider geographic range than brown trout. The two species had similar post- yearling abundances in allopatry and sympatry, and their abundances depended similarly on reach-level variation in the physical habitat. The species appeared to have dramatically different effects on native drift-feeding Aplochiton spp., which were virtually absent from streams invaded by brown trout but shared a broad sympatric range with rainbow trout. Within this range, the species’ post-yearling abundances varied independently before and after controlling for variation in the physical habitat. In the north of the island, Aplochiton spp. inhabited streams uninvaded by exotic trouts. Our results provide a context for investigating the mechanisms responsible for apparent differences in rainbow and brown trout invasion biology and can help inform conservation strategies for native fishes in Chilo ´e and elsewhere.
[Show abstract][Hide abstract] ABSTRACT: Chromosomal rearrangements have played a key role in the speciation of the New World sexual Artemia species (Crustacea, Anostraca) A. franciscana and A. persimilis. The species differ by a chromosome duplication (2n+2=44 in A. persimilis vs 2n=42 in A. franciscana), and a greater amount of heterochromatin (HCH) in A. franciscana. To investigate this difference in HCH, four parameters were compared for the first time in Artemia: 1) the absolute sizes of one A. persimilis and four A. franciscana karyotypes; 2) the relative lengths of all chromosome; 3) the number of heterochromatic bands and 4) the relative amounts of HCH per chromosome and its position. The two A.franciscana karyotypes with the largest HCH amount (26%), have twice (139.26 microm and 134.05 microm) the absolute size of the A.persimilis karyotype (64.91 microm; HCH: 1.97%). Interspecific and intraspecific (A. franciscana) differences in chromosome size and HCH were observed, although the two sets of information are not positively correlated. While A. persimilis shares plesiomorphic karyological traits with Old World species, A. franciscana has apomorphic features such as longer chromosomes and greater HCH content, mainly dispersed towards telomeres. The impacts of such chromosome rearrangements are discussed in relation to the wider geographic distribution, greater colonizing ability, and life history plasticity of A. franciscana. An additional, though preliminary, point of this paper is the observation that the female would be the heterogametic sex.
[Show abstract][Hide abstract] ABSTRACT: The brine shrimp Artemia is a well known animal extremophile adapted to survive in very harsh hypersaline environments. We compared the small stress proteins artemin and p26, and the chaperone hsc70 in encysted embryos (cysts) of the New World species, A. franciscana and A. persimilis. Cysts of the former, from San Francisco Bay, USA (SFB), were used essentially as a reference for these proteins, while both species were from locations in Chile where they occur in habitats at latitudinal extremes, the Atacama desert and Patagonia. These two species are phylogenetically distant, A. persimilis being closer to the Old World species, whilst A. franciscana is considered younger and undergoing evolutionary expansion. Using western blotting we found all three stress proteins in cysts from these five populations in substantial although variable amounts. The protein profiles revealed by Coomassie staining after electrophoresis (SDS-PAGE) were similar qualitatively, in spite of marked differences in the habitats from which these populations originated, and the long time since they diverged. We interpret these findings as further evidence for the adaptive importance of these three conserved proteins in coping with the variable, but severe stresses these encysted embryos endure.
Comparative biochemistry and physiology. Part A, Molecular & integrative physiology 05/2009; 153(4):451-6. · 2.20 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A preliminary biometric and ecologic database for the brine shrimp Artemia from Mexico and Chile is presented. The area abounds in small and seasonal ponds and large inland lakes, the latter mainly located in Mexico, although relatively large and isolated lakes are found in complex hydrological settings in pre-high plateau areas of Chile. This paper summarizes research efforts aimed at the localization, characterization, and evaluation of the aquaculture potential of Artemia populations in Mexico and Chile, which exhibit great habitat diversity (ponds, salterns, coastal lagoons, sea arms, coastal and inland lakes), contrasting weather conditions and different levels of isolation and human intervention.
This study covered locations between 29 degrees north latitude (Baja California, Mexico) to 50 degrees south latitude (Puerto Natales, Chile). Biological characteristics considered are species name, reproductive mode, cyst diameter, chorion thickness, and nauplius length, whereas ecological data include pond size, pH, salinity, temperature, and water ionic composition. Artemia franciscana is the only species found in Mexico, it exists together with A. persimilis in Chile, though separated geographically. Ecological differences in habitat exist between both regions but also within countries, a pattern particularly clear with regard to water composition. Surprisingly, a Mexican (Cuatro Ciénegas, A. franciscana) and a Chilean location (Torres del Paine, A. persimilis) share habitat characteristics, at least for the period when data were collected. The discriminant analysis for cyst diameter and nauplius length shows that Artemia from only one location match in cyst diameter with those from San Francisco Bay (SFB) (Point Lobos), and one (Marquez) is far apart from SFB and all the others. The Chilean locations (Pampilla, Cejar, Cahuil, Llamara, Yape) share cyst diameter, but tend to differ from SFB. The remaining Mexican locations (Juchitan, Ohuira, Yavaros) are well separated from all the others. With regard to nauplii length, populations tend to distribute in a relatively random manner, being Marquez the location differing the most in cyst diameter from SFB.
This database will contribute to the knowledge of radiation centers and serves as a baseline for further biogeographic studies, population characterization, management, and monitoring of Artemia biodiversity. Likewise, the impact of colonization and translocations for aquaculture purposes can be better assessed with a baseline for reference. Mexico and Chile exemplify the need to increase and further integrate regional information to tackle fundamental problems underlying practical utilization of Artemia.
Saline Systems 02/2006; 2:13. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Biodiversity can be measured at different hierarchical levels, from genetic diversity within species to diversity of ecosystems, though policy-makers tend to use species richness. The 2010 goal of reducing biodiversity loss, agreed by the subscribers to the Convention on Biological Diversity, requires simple and reliable protocols to evaluate biodiversity at any level in a given ecosystem. Stakeholders, particularly policy makers, need to understand how ecosystem components interact to produce social and economic benefits on the long run, whilst scientists are expected to fulfil this demand by testing and modelling ideally simple (low diversity) ecosystems, and by monitoring key species. This work emphasizes the unique opportunity offered by inland, isolated salt lakes and the brine shrimp Artemia, an example of biodiversity contained at the intra-specific level, as simple models to understand and monitor biodiversity, as well as to assess its predicted positive association with ecosystem stability. In addition to having well identified species and strains and even clones, that allow to test reproductive effects (sexual versus asexual), Artemia benefits from the possibility to set up experimental testing at both laboratory scale and outdoor pond systems, for which a comprehensive cyst bank with sufficient amount of samples from all over the world is available.
Saline Systems 02/2006; 2:14. · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Aim Two species of the brine shrimp, namely Artemia franciscana Kellogg and A. persimilis Piccinelli and Prosdocimi, inhabit Chile. Most studies so far have shown that A. franciscana is the most widely distributed species in Chile, with A. persimilis present only in Chilean Patagonia. In general, there is good agreement between morphological and genetic comparisons of Chilean populations with respect to species discrimination. However, a number of results indicate an overlap with some populations tending to diverge from A. franciscana and/or resembling A. persimilis. Prior to the mid 90's the use of DNA markers in Artemia was rather limited, despite their successful application in numerous other species. In this study, we investigate whether the conclusions drawn from traditional comparative tools are congruent with the pattern of genetic divergence depicted by DNA analysis at the mitochondrial level.Location Eight sites in Chile and two reference samples of A. franciscana and A. persimilis from San Francisco Bay (USA) and Buenos Aires (Argentina), respectively.Methods Restriction fragment length polymorphism (RFLP) analysis of a 535 bp segment of the mitochondrial 16S rRNA gene with nine restriction enzymes in 240 individuals.Results No haplotype was shared between the two species. Five restriction enzymes produced species-specific patterns, enabling the unambiguous assignment of populations to species. Very high (100%) bootstrap values supported the clustering of haplotypes in two groups corresponding to the two species. The two species were clearly differentiated with average sequence divergence of 12.3%. High genetic differentiation was also found among con-specific populations of A. franciscana with an FST estimate of 91%.Main conclusions The mitochondrial DNA (mtDNA) results of this study show a broadly similar pattern to those of previous allozyme and nuclear DNA analyses, with the two New World species appearing as highly divergent. The presence of A. persimilis in southern Chile (Chilean Patagonia) was confirmed. Hence, a species previously regarded as geographically restricted mainly to Argentina, appears to have expanded its range. Populations of A. franciscana appear highly structured with a level of inter-population genetic differentiation much higher for mtDNA than previously reported with allozymes. Clustering of these populations does not follow a clear geographic pattern. The identification of population-specific genetic markers for A. persimilis and A. franciscana will help to tackle further aspects of the speciation patterns of these species.