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Geographic distributions of homosporous ferns: Does dispersal obscure evidence of vicariance?
Abstract
The central problem in biogeography is that interactions between different processes result in the formation of historical patterns, such that it is difficult to discriminate the relative roles of vicariance and dispersal. Ferns are distributed by small wind-dispersed propagules that are produced in very large numbers and capable of dispersing thousands of kilometers. Thus, most taxon distributions in ferns are assumed to be a function of dispersal rather than vicariance. Here, we review some case examples that provide good evidence for vicariance and dispersal in ferns. We then ask whether dispersal is so extensive in ferns that vicariance is no longer detectable in most cases. Although we think that too few studies have been carried out to make generalizations at this stage, we outline the criteria for an effective research programme that can address this issue. Phylogenetic and distributional data are needed, not only because they are lacking in an evolutionarily important group of organisms, but also because data from ferns and other cryptogams are likely to be crucial in making broad biogeographic statements.
... Beginning with Asa Gray (1859Gray ( , 1878, numerous botanists have puzzled over the pattern of disjunction between East Asian and eastern North American floras (Li, 1952;Barrington, 1993;Kato,1993;Xiang et al., 2000;Wolf et al., 2001;Moran, 2008;Xiang et al., 2015;Li et al., 2016). Using ribulose 1, 5-biphosphate carboxylase/oxygenase large subunit (rbcL) gene sequences for reconstruction of angiosperm phylogeny and molecular clock divergence time estimation coupled with fossil calibration, Xiang et al. (2000) concluded that congruent vicariance associated with climatic cooling during the late Neogene and Quaternary was the best explanation for disjunction between East Asian and eastern North American angiosperms. ...
... Among those ferns first described by Gray (1859) as exhibiting an East Asian-eastern North American disjunction were varieties of Osmunda cinnamomea L. and Onoclea sensibilis L. (Li, 1952). Although it is postulated that climatic cooling during the late Neogene and Quaternary was also responsible for vica riance in O. sensibilis, long-distance dispersal by wind-blown spores has not yet been ruled out (Barrington, 1993;Kato, 1993;Wolf et al., 2001;Xiang et al., 2015). Moreover, preliminary investigations within specific fern clades, such as Osmundaceae Martinov, using similar rbcL and fossil evidence have suggested that the East Asian-eastern North American disjunctions in O. cinnamomea and O. claytoniana L. (syn. ...
... Claytosmunda claytoniana (L.) Metzgar et Rouhan) were incongruent with the pattern observed among angiosperm lineages, as separate episodes of evolutionary divergence coupled with biogeographic disjunction have been dated to the Paleogene rather than the late Neogene/Quaternary: 35 Ma (Eocene) and 25 Ma (Oligocene), respectively (Yatabe et al., 1999). Furthermore, intercontinental disjunctions among fern species are frequently explained by long-distance dispersal of wind-blown spores rather than by vicariance (Wolf et al., 2001;Sessa et al., 2017). ...
Disjunction between East Asian and eastern North American plants has been recognized since the time of Darwin. Although there is considerable evidence for congruent vicariance associated with late Neogene/Quaternary cooling among angiosperms, similar studies among specific fern families (e.g., Osmundaceae Martinov) have appeared incongruous with this pattern. Pteridologists continue to debate whether long-distance dispersal of wind-blown spores could have produced intercontinental disjunctions among ferns. To date, however, state-of-the-art historical biogeographical approaches have not been applied to this problem. In this investigation, multiple chloroplast gene (rbcL, atpA, atpB, and matK) sequences for ferns in the family Onocleaceae Pic. Serm. are drawn from GenBank, including those from the recently sequenced chloroplast genome of the East Asian fern O. sensibilis L. var. interrupta Maxim., and used to create molecular phylogenies using Bayesian (BEAUTi and BEAST) techniques. Using contemporary approaches for relaxed molecular clock divergence time estimation with fossil calibration, divergence time estimates for East Asian and eastern North American populations in the Onoclea sensibilis species complex are consistently reconstructed as the Pliocene (ca. 5 – 3.4 Ma), and the best-fitting historical biogeographic model is a DIVA-like (exclusively vicariant) model using BIOGEOBEARS in RASP4, with a low probability of peripatry. Accordingly, these molecular and fossil data appear congruent with the pattern observed among angiosperms, despite the propensity for long-distance dispersal of wind-blown spores in pteridophytes. The lack of evidence for peripatry in this lineage may be related to the presence of short-lived green spores in onocleoid ferns; however, this hypothesis requires further investigation.
... Pteridophytes, including lycophytes and monilophytes, are organisms with high dispersive capacity [39], by spores, which favors population connectivity and decreased genetic structure [40]. This may account for its low levels of endemism by comparison with angiosperms, as occur in Macaronesia. ...
... In ferns, the reproductive system is closely related to the colonizing capacity of the species. The colonization of new habitats will be more likely for those species with intragametophytic selfing, which are able to establish a new population even from just one spore [39,44]. In herbaceous plants with clonal reproduction, after an initial founder event by one or few genotypes, the expansion process can occur via vegetative reproduction (e.g., [102,103]). ...
Macaronesia has been considered a refuge region of the formerly widespread subtropical lauroid flora that lived in Southern Europe during the Tertiary. The study of relict angiosperms has shown that Macaronesian relict taxa preserve genetic variation and revealed general patterns of colonization and dispersal. However, information on the conservation of genetic diversity and range dynamics rapidly diminishes when referring to pteridophytes, despite their dominance of the herbaceous stratum in the European tropical palaeoflora. Here we aim to elucidate the pattern of genetic diversity and phylogeography of Diplazium caudatum, a hypothesized species of the Tertiary Palaeotropical flora and currently with its populations restricted across Macaronesia and disjunctly in the Sierras de Algeciras (Andalusia, southern Iberian Peninsula). We analysed 12 populations across the species range using eight microsatellite loci, sequences of a region of plastid DNA, and carry out species-distribution modelling analyses. Our dating results confirm the Tertiary origin of this species. The Macaronesian archipelagos served as a refuge during at least the Quaternary glacial cycles, where populations of D. caudatum preserved higher levels of genetic variation than mainland populations. Our data suggest the disappearance of the species in the continent and the subsequent recolonization from Macaronesia. The results of the AMOVA analysis and the indices of clonal diversity and linkage disequilibrium suggest that D. caudatum is a species in which inter-gametophytic outcrossing predominates, and that in the Andalusian populations there was a shift in mating system toward increased inbreeding and/or clonality. The model that best explains the genetic diversity distribution pattern observed in Macaronesia is, the initial and recurrent colonization between islands and archipelagos and the relatively recent diversification of restricted area lineages, probably due to the decrease of favorable habitats and competition with lineages previously established. This study extends to ferns the concept of Macaronesia archipelagos as refugia for genetic variation.
... They assume different patterns of coverage, occurrence or non-occurrence, which results in the floristic heterogeneity and the peculiar composition of each site, even in spatially close areas, corroborating with studies by Rodrigues and Nave (2000); Carvalho et al. (2005) and Mallmann et al. (2016). In addition, in the specific case of ferns and lycophytes, floristic dissimilarity is influenced by intrinsic factors, such as spores dispersion (Jones et al. 2006), which occurs close to mother plants (Wolf et al. 2001) or vegetative (Jones et al. 2007), restricting their distribution to short distances (less than 100m) on a regional scale (Jones et al. 2006). ...
... They assume different patterns of coverage, occurrence or nonoccurrence, which results in the floristic heterogeneity and the peculiar composition of each site, even in spatially close areas, corroborating with studies by Rodrigues and Nave (2000); Carvalho et al. (2005) and Mallmann et al. (2016). In addition, in the specific case of ferns and lycophytes, floristic dissimilarity is influenced by intrinsic factors of spore dispersion (Jones et al. 2006), which occurs close to the mother plant (Wolf et al. 2001) or vegetatively (Jones et al. 2007), restricting their distribution to short distances (less than 100m) on a regional scale (Jones et al. 2006). ...
Riparian forests are heterogeneity due to biological and abiotic variables that influence
environmental dynamics. The aim of this study was to investigate the floristic and environmental dissimilarity in three riparian forest fragments. In a 250 m transect ten plots of 5 × 5 m were drawn in each fragment, totaling 30 plots. Floristic inventories were conducted. Abiotic variables (soil moisture and canopy opening) were measured and the environmental quality was evaluated through the Rapid Assessment Protocol of Habitat Quality (RAPHQ). A total of 25 species were recorded in 20 genera and 12 families following the asymptote tendency for each fragment. The fragments revealed high diversity and most species were distributed in diverse genera (FI: 12 species in 10
genera; FII: 13/11 and FIII: 14/14). Only three species were present in all fragments. In general, at least 44% of the species were shared at two or more sites. Our results indicated floristic and community heterogeneity among the fragments analyzed (R = 0.621 global, P = 0.001). Our findings showed that in FI and FII, environmental variations, such as lower scores in RAPHQ and soil moisture reflected in lower species coverage, and more homogeneous plant distribution. In FIII, the same environmental variables resulted greater coverage of plants, and a more heterogeneous and equitable distribution among the plots. These results demonstrate that ferns and lycophytes are important tools to evaluate environmental dissimilarity in riparian forests, reasserting the bioindicator potential of these plants.
... Apesar de ampla distribuição geográfica de muitas espécies através da dispersão à longa distância por esporos (Tryon 1970;Barrington 1993;Wolf et al. 2001), algumas espécies de samambaias e licófitas apresentam restrições às condições ecológicas, principalmente quanto à temperatura, umidade, estrutura e qualidade da matriz florestal e composição dos substratos, tanto para o desenvolvimento dos esporófitos, como para a germinação de esporos e fixação dos gametófitos (Page 1979). Tais condições fazem com que a distribuição das espécies ao longo dos ecossistemas não seja uniforme, tornando algumas espécies raras, ou com distribuição limitada à habitats muito particulares, e consequentemente passíveis à efeitos extintivos (Mehltreter 2010). ...
... Embora haja uma prevalência de espécies de ampla distribuição geográfica dentre as distintas fitofisionomias ocorrentes no RS (Sehnem 1977;Lorscheitter et al. 1998;1999;2001;2002;, algumas espécies como Diplazium plataginifloium (Fig. 3a), D. riedelianum (Fig. 5b), Danaea moritziana, Campyloneurum rigidum, Adiantum pentadactylon (Fig. 5d), e outras (Tab. 1), apresentam no RS distribuição limitada às formações de Floresta Ombrófila Densa. ...
Resumo Um inventário de samambaias e licófitas da Reserva Biológica Estadual Mata Paludosa (REBIO Mata Paludosa), Itati, Rio Grande do Sul, Brasil, é apresentado. Durante o período de um ano, as espécies ocorrentes na REBIO foram registradas, com amostras coletadas e incorporadas no herbário HUCS. As espécies foram classificadas quanto ao hábito, grau de ameaça e sua ocorrência nas distintas fitofisionomias do Rio Grande do Sul. No total foram encontradas 79 espécies, sendo uma licófita e 78 samambaias. As famílias de maior riqueza florística foram Polypodiaceae (12), Dryopteridaceae, Pteridaceae e Thelypteridaceae (10 espécies cada) e Aspleniaceae (nove). As plantas terrestres foram as mais representativas (64%), seguidas pelas epífitas (28%) e hemiepífitas (8%). A maioria das espécies tem padrão de distribuição amplo no Rio Grande do Sul (75%). Encontrou-se populações de cinco espécies localmente ameaçadas de extinção. A REBIO Mata Paludosa representa importantes remanescentes da Mata Atlântica no Estado do Rio Grande do Sul, por apresentar elevada riqueza florística de samambaias e licófitas, espécies de distribuição restrita e ameaçadas de extinção localmente.
... The propagules of ferns are very small spores (~40-80µm) produced in vast quantities (Moran 2004). Because of this, it has been theorised that fern spores can be carried by wind to essentially anywhere on the planet (Tryon 1970;Wolf et al. 2001). In fact, the elevated proportion of ferns on oceanic islands has been used as evidence of their dispersibility (Tryon 1970;Smith 1972;Peck et al. 1990). ...
Biologists have long pondered species' geographical distributions and sought to understand what factors drive dispersal and determine species ranges. In considering plant species with large ranges, a question that has remained underexplored is whether large ranges are attained primarily through many instances of short scale dispersal or whether instead widespread ranges are attained by propagules with increased dispersal distances. Ferns provide an ideal system to explore this question as their propagules are very small spores, which have been theorised can be carried by wind to essentially anywhere on the planet. Unfortunately, population-level genetic data in ferns is relatively uncommon, limiting our ability to answer this and related questions. For this work, I focus on Cheilanthes distans (Pteridaceae) as a study system, a widespread fern with extensive spore variation that occurs over Australia and into New Zealand/Aotearoa, New Caledonia, and other Pacific islands. I sampled widely across the species' range, in addition to across Australasian Cheilanthes (as a robust tree for the genus does not exist), ultimately building a phylogeny based on the GoFlag 451 bait set. With these data, we can investigate additional questions, including whether reproductive mode, polyploidy, or lineage influence dispersal, as well as whether movement is occurring randomly or is instead asymmetrical. I explored the relationships between sexual and apomictic specimens to understand whether the former are the parental lineages to apomictic plants and whether we find evidence for apomictic plants dispersing out of a small parental range. I investigated how many times polyploid lineages have arisen in C. distans and whether they are each limited geographically, perhaps forming isolated ranges that collectively result in C. distans' larger range. Additionally, I generated estimates for ancestral ranges and dispersal between populations to understand whether certain lineages are limited to particular geographic regions, to explore the directionality of dispersal, and to assess whether most movement is happening over short or long distances. Particularly interestingly, I find that most dispersal in this species appears to occur over smaller steps rather than longer jumps, underscoring how short movement can nevertheless allow for establishment of large ranges; this dispersal is not limited phylogenetically and seems to occur equally for all lineages. What is more, I find evidence for asymmetrical dispersal directionality, apparently most frequently tracking trade winds. These findings demonstrate the importance of population-level data, and provide concrete results that add nuance to long-standing dispersibility hypotheses in the fern community that have, until now, lacked empirical data.
... Among vascular plants, the propagules of ferns are in fact particularly dispersible given the small sizes of spores and their light weight, which is lighter than the smallest seeds and even than the pollen of several wind-dispersed species (Gómez-Noguez et al. 2016 and references therein). It has been theorised that spores can be carried essentially anywhere on the planet (Tryon 1970;Wolf et al. 2001); their higher proportions relative to other vascular plants on oceanic islands (vs. the mainland) in part supports this conclusion (Tryon 1970;Smith 1972;Peck et al. 1990). If we assume that everything is in fact everywhere with relation to fern spores, then spore variation becomes unimportant-and thus unworthy of study-because we are assuming that spores of all sizes will arrive at any given location. ...
Biological trade-offs present a central issue for evolutionary biology: it has been a fundamental understanding within the field that limits exist on the phenotypic traits a species is able to exhibit in part due to trade-offs. Reproduction-with its myriad forms-has been studied extensively in the context of these dynamics. And while considerable literature has explored trade-offs between seed size and number and their associated environmental conditions, none has looked at spore size trade-offs in ferns. We can hypothesise potential trade-offs in spore size: smaller spores should be able to disperse farther, but may not have sufficient provisions to survive in environments that require them to remain at the gametophyte stage for longer periods if their germination cues are mismatched. Reproductive mode (sexual vs. asexual) and ploidy may also be playing a role. In order to study trade-offs related to spore size, I focus on the Australasian fern species Cheilanthes distans (Pteridaceae), which is most often found in xeric environments, growing in crevices or on top of rocks which are haphazardly scattered across their range. Apomictic diplospores in this species are formed through first division restitution, a meiotic pathway particularly prone to mistakes in chromosome pairing and cell division (as compared to premeiotic endomitosis). Rather than being problematic, these mistakes ultimately lead to considerable additional variation in spore size, spore products (through a range of aneuploid spores), and spore ploidy. In this study, I explore trade-offs between spore size, dispersal, and germination, taking into account effects from reproductive mode and ploidy. I carried out an extensive survey of C. distans specimens to establish the prevalence of sexual vs. apomictic (asexual) specimens, and to describe in greater depth the variation in ploidy across the species. I also collected data on spore size and sporogenesis forms. With these data I then asked: is spore size correlated with range area or with germination? And does spore form correlate with either spore size or germination? Ultimately, I find that variations in sporogenesis may be leading to large variation in spore sizes-especially since spores traditionally considered abortive are in fact viable-and that this variation may provide abundant fodder for evolution to act through trade-offs between dispersal into large ranges and germination leading to establishment. Especially in light of the fact that many spores that were historically considered abortive are fully viable and likely shaping evolution in important ways, it is worth remarking on what these results illustrate more broadly: the way in which we have constructed 'disability' ultimately affects how we perceive so-called 'genetic errors'-both in humans and in other species-and thus limits what we allow ourselves to imagine 'disabled' beings are capable of.
... The characteristics of C. macrocarpa populations with dispersal signatures are consistent with strong bottlenecks due to recent founder events by one or few genotypes, followed by expansion through vegetative reproduction. This phenomenon is known in clonal herbaceous plants (e.g., [87,88]) and particularly in ferns, where most homospore ferns are believed to establish populations from a single spore via intra-gametophytic selfing [9,82,89]. For example, this colonization strategy (single-spore colonization and subsequent population establishment) was proposed for the post-glacial colonization of Europe by Asplenium trichomanes subsp. ...
The tree fern Culcita macrocarpa, a threatened Iberian–Macaronesian endemism, represents the sole European species of the order Cyatheales. Considered a Tertiary relict of European Palaeotropical flora, its evolutionary history and genetic diversity, potentially influenced by presumed high clonal propagation, remain largely unknown. This study elucidates the phylogeographic history of C. macrocarpa, assessing the impact of vegetative reproduction on population dynamics and genetic variability. We provide genetic data from eight newly identified nuclear microsatellite loci and one plastid DNA region for 17 populations spanning the species’ range, together with species distribution modeling data. Microsatellites reveal pervasive clonality in C. macrocarpa, which has varied among populations. We assess the impact of clonality on genetic diversity and evaluate how estimates of intra-population genetic diversity indices and genetic structuring are affected by the chosen definition of “individual” (focusing exclusively on genetically distinct individuals, genets, as opposed to considering all independent clonal replicates, ramets). We identify two main population groups, one in the northern Iberian Peninsula and the other in the Macaronesian archipelagos and southern Iberian Peninsula. Within each group, we found relict populations (in the Azores and the Cantabrian Cornice) as well as recent originated populations. This population structure suggests colonization dynamics in which recent populations originated from one or a few genets of relict populations and became established through intra-gametophytic self-fertilization and vegetative expansion. DAPC analysis facilitated the identification of alleles that most significantly contributed to the observed population structure. The current Andalusian populations appear to have originated from colonization events from the Azores and the Cantabrian Cornice. Our findings suggest that C. macrocarpa persisted through the Last Glacial Maximum in two refugia: the Azores and the Cantabrian Cornice. Colonization into new areas occurred presumably from these refuges, generating two large population groups with structured genetic diversity. This study underscores the significance of clonality in establishing new populations and shaping genetic structure.
... They generate a large number of spores, which are dispersed over long distances, enabling them to colonize new habitats and establish a wide geographical range (1). The spores are light and small, typically measuring less than 0.1 mm in both the equatorial and polar axis, making them capable of dispersal by wind over thousands of kilometers (2,3). These spores are also able to survive in soil for several years, forming spore banks, and can germinate after disturbances, becoming primary colonizers in disturbed habitats and barren land (1). ...
In the current investigation, an attempt has been made to document the floristic diversity and chorotype analysis of Pteridophytes growing in Zimbabwe. Previously published literature and online sources were consulted to confirm the nomenclature, precise locations, chorotype, stages of invasion, and conservation status of the Pteridophytes in Zimbabwe. The updated list of Pteridophyte taxa confirms that there are 297 taxa belonging to 83 genera and 19 families. The largest family is Aspleniaceae, with 78 taxa (26.26%), followed by Polypodiaceae and Pteridaceace with 67 taxa (22.56%) and 54 taxa (18.18%), respectively. The largest genus is Asplenium L., with 46 taxa (15.49%), followed by Hemionitis L. with 22 taxa (7.41%), Ophioglossum L. (16 taxa, 5.39%), Thelypteris Schmidel (14 taxa, 4.71%), and Elaphoglossum Schott ex J.Sm. (12 taxa, 4.04%). A total of 20 taxa (6.73%) are threatened with extinction, emphasizing the need for detailed knowledge of the nomenclature, conservation status, and distribution of Pteridophytes taxa in Zimbabwe. Research focusing on the diversity, ecology, and conservation status of Pteridophytes is imperative for biodiversity conservation, as they are an important component of natural ecosystems adapted to different habitats. Therefore, future studies on Pteridophytes in Zimbabwe should explore how the lack of floristic data on the plant group can hinder ecological research.
... Although some of the palynomorphs recorded in this study from the palaeo-island could have been directly transported from the mainland by air or water currents, it is likely that many of the taxa originate from plants growing on the island that derive from populations established by long-distance transport of spores or other propagules. Many fern spores are dispersed by wind (Tryon, 1970(Tryon, , 1986 and, in open environments, such spores can readily disperse a few kilometres, and a small percentage of can disperse much greater distances (Kato, 1993;Wolf et al., 2001;Kessler, 2010). Homosporous plants (i.e., bryophytes and most ferns) have some advantages for long-distance dispersal, as the free-living gametophyte emerges from the spore, is self sustaining and produces a new sporophyte generation, in contrast to the sporophyte-dependent gametophytes of gymnosperms (Rose and Dassler, 2017). ...
Palynological assemblages from palaeo-islands are scarce in the fossil record and represent an opportunity to explore plant dispersal patterns and colonization strategies in isolated ecosystems. We present a palynological study of a Middle Jurassic volcanic island located in a shallow epicontinental sea, c. 150 km from the palaeo-mainland. The study is based on a 2-m thick succession of calcareous marlstones in the El Pedregal Formation in the eastern part of the Iberian Basin, and the palaeo-island is termed Camarena Island after the village nearest to the fossil site. Eleven samples yielded equivalent assemblages that are here treated as a single palynological suite containing 47 fossil-species belonging to 36 fossil-genera. The abundance of Araucariacites australis andKlukisporites variegatus, together with accessory Cycadopites spp. and the scarcity of Callialasporites turbatus, Manumia irregularis, Staplinisporites caminus and Kekryphalospora distincta, suggest a Toarcian–Aalenian age. Additional stratigraphical data resolve the likely age for the Camarena Island as lower–middle Aalenian. Many palynomorphs in this assemblage have apparent anemophilous and hydrophilous adaptations facilitating long-distance transport. On this basis, some parent plants probably derive from the adjacent mainland or neighbouring islands. Marine palynomorphs or pollen and spores with few adaptations for dispersal may have derived from plant groups that evolved in situ on the volcanic island. The palynological assemblage has some differences from coeval palynofloras from the central Iberian Peninsula, but there are also some similarities with assemblages from post-volcanic deposits and other oceanic islands. It is likely that the seaway separating the volcanic island from the mainland acted as a biological filter enabling colonization by only a selected range of plant groups.
... Despite this collective effort in sporangia production and, in addition to the fact that the ferns produce a larger number of positive photoblastic spores that persist in the soil for long periods, sexual reproduction is somewhat rare (Esteves 2013;Arens 2001). The preferential dispersion is vegetative (Jones et al. 2007) or near mother plants (Wolf et al. 2001), which restricts its distribution to short distances, since its spores are really small (Jones et al. 2006(Jones et al. , 2007. ...
Although ferns have a prominent floristic position with their richness center in Atlantic Forest in Brazil, the effect of climate on their phenophases is still poorly known. This group shows different phenological patterns due to the great latitudinal extent, the strong climatic seasonality of this forest, and the leaf dimorphism found in some species. In this scenario, we evaluated the phenological events of Elaphoglossum macrophyllum and related them to climatic factors. Fertility, leaf renewal, and leaf senescence in E. macrophyllum were analyzed based on the monthly survey of 152 plants growing for two years in the subtropical Atlantic Forest, Brazil. The three analyzed phenophases showed the same intra-annual pattern regarding continuity, regularity, and seasonality along the two years, revealing a phenological pattern for the specie. The generalized additive models for location, scale, and shape (GAMLSS) indicated that photoperiod was the most important trigger for fertility and leaf renewal. Temperature, as an important phenology modulator, was related to leaf renewal and senescence. Our data indicate that E. macrophyllum, an endangered species in southern Brazil, withstands the consequences of seasonal climatic variations without the individual mortality, total leaf shedding, or fertility loss.
... However, it is also conceivable that this early split is the result of a vicariance event as a result of the continental breakup between America and Africa. Although this continental breakup took place some 30-50 Ma before the split of the lineages, the continents were still fairly close to each other for quite a time, and it is conceivable that for a spore-dispersed plant group such as ferns, the narrow oceanic gap may not have immediately led to disruption of gene flow, resulting in a more recent dating of the separation (Wolf et al., 2001;Noben et al., 2017). Especially if the oldest acceptable age estimate (87.62 Ma) of the initial separation is used, it fits the Gondwana-related vicariance even better. ...
The pantropical fern genus Didymochlaena (Didymochlaenaceae) has long been considered to contain one species only. Recent studies have resolved this genus/family as either sister to the rest of eupolypods I or as the second branching lineage of eupolypods I, and have shown that this genus is not monospecific, but the exact species diversity is unknown. In this study, a new phylogeny is reconstructed based on an expanded taxon sampling and six molecular markers. Our major results include: (i) Didymochlaena is moderately or weakly supported as sister to the rest of eupolypods I, highlighting the difficulty in resolving the relationships of this important fern lineage in the polypods; (ii) species in Didymochlaena are resolved into a New World clade and an Old World clade, and the latter further into an African clade and an Asian-Pacific clade; (iii) an unusual tripling of molecular, morphological and geographical differentiation in Didymochlaena is detected, suggesting single vicariance or dispersal events in individual regions and no evidence for reversals at all, followed by allopatric speciation at more or less homogeneous rates; (iv) evolution of 18 morphological characters is inferred and two morphological synapomorphies defining the family are recognized-the elliptical sori and fewer than 10 sori per pinnule, the latter never having been suggested before; (v) based on morphological and molecular variation, 22 species in the genus are recognized contrasting with earlier estimates of between one and a few; and (vi) our biogeographical analysis suggests an origin for Didymochlaena in the latest Jurassic-earliest Cretaceous and the initial diversification of the extant lineages in the Miocene-all but one species diverged from their sisters within the last 27 Myr, in most cases associated with allopatric speciation owing to geologic and climatic events, or dispersal.
... Fern diversity and composition in local and regional assemblages are considered to reflect environmental sorting (Kreft et al., 2010;Khine et al., 2019), rather than biotic interaction (Hernández-Rojas et al., 2021). Because ferns are dispersed by spores which can travel thousands of kilometers by wind (Wolf et al., 2001), their distributions are thought to be more in equilibrium with climate than most of seed plants (Qian, 2009). Ferns are considered to be good climate indicators, and an ideal group for understanding geographic and ecological patterns of biodiversity across the globe (Khine et al., 2019). ...
Knowledge of relationships between phylogenetic structure of a biological assemblage and ecological factors that drive the variation of phylogenetic structure among regions is crucial for understanding the causes of variation in taxonomic composition and richness among regions, but this knowledge is lacking for the global flora of ferns. Here, we fill this critical knowledge gap.
We divided the globe into 392 geographic units on land, collated species lists of ferns for each geographic unit, and used different phylogenetic metrics (tip‐ vs basal‐weighted) reflecting different evolutionary depths to quantify phylogenetic structure. We then related taxonomic and phylogenetic structure metrics to six climatic variables for ferns as a whole and for two groups of ferns (old clades vs polypods) reflecting different evolutionary histories across the globe and within each continental region.
We found that when old clades and polypods were considered separately, temperature‐related variables explained more variation in these metrics than did precipitation‐related variables in both groups. When analyses were conducted for continental regions separately, this pattern holds in most cases.
Climate extremes have a stronger relationship with phylogenetic structure of ferns than does climate seasonality. Climatic variables explained more variation in phylogenetic structure at deeper evolutionary depths.
... 10% of the Hawaiian vascular flora, compared to 0.4% worldwide. Ferns appear overrepresented on oceanic islands (Kreft et al. 2010), probably because of their high capacities for long-distance dispersal via their small spores (Wolf et al. 2001). In the Hawaiian Islands, ferns are found in nearly all terrestrial ecosystems. ...
The Hawaiian Islands are an emblematic field to study evolution, with their very high rates of endemism and spectacular cases of insular speciation. Nevertheless, many Hawaiian lineages still deserve investigation, such as in the fern lineage. In this study, we address the question of the origin of the fern genus Ctenitis, which is present in the archipelago with two endemic species, Ctenitis squamigera and C. latifrons. Using a taxonomic sampling covering the pantropical distribution of the genus and three chloroplast DNA regions, we provide evidence that the genus in the Hawaiian Islands originated from a single long-distance dispersal from the Neotropics. This area is less represented than Asia and the South Pacific in the origin of Hawaiian ferns, but a Neotropical origin may be explained by the transportation of spores by tropical storms originating near Central America. Furthermore, the colonization of the Hawaiian Islands is estimated to have occurred between 4 [9-2] and 3 [7-1] mya. This timing is consistent with the ages of all main and extant islands of the archipelago, which already provided habitats for the establishment of the initial Ctenitis colonizer. In turn, this relatively late arrival to the islands and the related potentially low availability of ecological niches may have hampered diversification of the genus beyond the two extant species.
... Sw. is capable of housing 256-minute spores that can easily adhere to surfaces causing the unintended spread of this invasive species. The size of its spore ranges from 64-80 μm in diameter (Murtaza et al., 2004) which therefore caters to long distance dispersal , Barrington et al., 2020 that can be easily carried through wind (Wolf et al., 2001) and water due to its size. Rainwater run-off and flooding may act as the main pathway towards infiltration of natural ecosystems increasing the potential of spores to move in a wider distribution. . ...
The Japanese climbing fern Lygodium japonicum (Thunb.) Sw. has manifested its invasive tendencies, not just in countries outside of its native origin, but also in some areas of its original distribution. The proliferation of such species resulted in economic instability and ecological damage which alarms ecologists, environmentalists and area managers. Thus, it is important to understand the mode of introduction and proliferation of such species to be able to prepare and formulate specific and effective guidelines in managing future invasion of such species. This paper discussed the contribution of trading, importation and transport of wildlife in the introduction of and spread of L. japonicum. The reproductive biology of the Japanese climbing fern has been reviewed to highlight the role of vegetative reproduction and spores in the immense proliferation of this species, and the challenges it imposes in the control and regulation of its spread. Containment and isolation of the invasive species is still considered as the best preventive method to avoid the invasion of L. japonicum, but in the occurrence of infestation, available research-based control methods must be applied. Existing control methods were included in this review with the addition of general considerations regarding the application of each method. Management plans are recommended to be formulated specific for L. japonicum (Thunb.) Sw. and applied in a long-term approach to achieve and ensure effective and sustainable practices and strategies in regulating invasion.
... Ferns, which originated over 400 million years ago (Testo and Sundue 2016), are the second most diverse lineage of vascular plants (Hernández-Rojas et al. 2021), with about 11 500 species worldwide (Hassler 2004-2021, Qian et al. 2022b. Because ferns are dispersed by spores that can travel thousands of kilometers by wind (Wolf et al. 2001), their distributions are thought to be more in equilibrium with climate than those of most seed plants (Qian 2009). Further, because the stomatal control of ferns is less efficient, compared with angiosperms (Brodribb and McAdam 2011), they appear to be more susceptible to limited water availability and are therefore considered to be good climate indicators (Khine et al. 2019). ...
Many biodiversity hotspots are located in montane regions, thus, understanding the underlying mechanisms driving species assembly along elevational gradients is of major interest in ecology and biogeography. Here, we assess spatial patterns and climatic drivers, and the effects of clade age, on patterns of phylogenetic structure of ferns along the world's longest elevational gradient in the central Himalaya. We used correlation and regression analyses to relate metrics of phylogenetic structure reflecting both shallow (tip‐weighted) and deep (basal‐weighted) evolutionary histories of ferns, and their two major groups reflecting different ages (polypods representing a young clade, all other ferns representing old clades), in fifty 100‐m vertical bands to climatic factors representing different aspects of climatic conditions (mean climate, stressful climate and climate seasonality). Variation partitioning analysis was used to determine the relative importance of each group of climatic factors on phylogenetic structure. We find that the composition of fern assemblages along the Himalayan elevational gradient in Nepal shows strong signatures of evolutionary processes. In a simplified way, species‐rich assemblages at mid‐elevations are likely the result of recent radiations in combination with low extinction rates, whereas species‐poor assemblages at low elevations are composed of numerous lineages with limited radiations, and those at high elevations of few lineages, also with limited signature of recent radiations. Variables related to temperature and climatic extremes tended to play a more important role than precipitation‐ and seasonality‐related variables, respectively, in driving fern phylogenetic structure. Combining the results of ferns and angiosperms suggests that there are a few generally consistent evolutionary processes that apply to all plant groups (e.g. niche conservatism and environmental filtering), but that the specific outcomes of these processes vary with elevation, clade age and taxon.
... Fern biogeography is typically challenging because vicariance patterns can often be conflated with longdistance dispersal (Wolf et al., 2001). Cumulative biogeographic histories of multiple reticulate evolution events, incomplete lineage sorting and differing local extinction patterns can also mask vicariance patterns (Barrington, 1993). ...
Asplenium scolopendrium is distributed in northern temperate forests with many global biogeographic disjunctions. The species complex of A. scolopendrium has been generated by spatial segregation coupled with divergent evolution. We elucidated the biogeographic history of the A. scolopendrium complex by exploring its origin, dispersal and evolution, thus providing insights into the evolutionary history of the Tertiary floras with northern pan-temperate disjunct distributions. The results revealed that all infraspecific taxa descended from a widely distributed common ancestor in the Northern Hemisphere. This pan-temperate ancestral population formed by unidirectional westward dispersal from European origins primarily during the Early Eocene when the Earth’s climate was much warmer than today. The splitting of European, American and East Asian lineages occurred during the Early Miocene due to geo-climatic vicariances. Polyploidy events in the American ancestral populations created additional reproductive barriers. The star-shaped haplotypes in each continent indicated that local disjunctions also led to derived genotypes with potential to diverge into different taxa. This intracontinental lineage splitting is likely related to latitudinal range shift and habitat fragmentation caused by glacial cycles and climate change during the Pleistocene. The evolutionary history of the A. scolopendrium complex supported the Boreotropical hypothesis exhibiting range expansion during the Early Eocene Climatic Optimum.
... suitable habitat is dependent on the individuals' dispersal ability, landing in appropriate habitat, and stable population establishment (Angert et al., 2011;Wolf et al., 2001). Although ferns generally have greater potential to disperse their spores over long distances than seed plants (Ranker & Haufler, 2008), an inability to adapt to the changing environment may lead to local or global extinction (Given, 1993). ...
Climate change is predicted to affect species in aquatic ecosystems. In Africa, factors that may influence the responses of aquatic species are poorly studied and challenging to predict. In this study, we examined the potential distribution of three aquatic fern species in the genus Azolla in Africa under projected climate change scenarios. MaxEnt was used to create ecological niche models of the three species using occurrence data and environmental variables. All models had satisfactory AUC and TSS values, indicating high prediction precision (AUC and TSS > 0.801). Results showed that elevation and precipitation were the most important variables limiting the species' expansion in the future. In addition, we observed significant variations in the climatic niches of the three species and their distinct climatically appropriate regions. The current potential distribution ranges for the species varied between 2,328,726 km2 and 4,026,363 km2. According to the model predictions for the current period, the potential range of Azolla species extended outside the known and recorded locations; however, under future climate conditions, the species were projected to lose between 8.1% and 48% of their suitable habitats due to climate change. Our findings can be used to develop sustainable conservation measures for aquatic species and raise awareness about the effects of climate change.
... 10% of the Hawaiian vascular flora, compared to 0.4% worldwide. Ferns appear overrepresented on oceanic islands (Kreft et al. 2010), probably because of their high capacities for long-distance dispersal via their small spores (Wolf et al. 2001). In the Hawaiian Islands, ferns are found in nearly all terrestrial ecosystems. ...
The Hawaiian Islands are an emblematic field to study evolution, with their very high rates of endemism and spectacular cases of insular speciation. Nevertheless, many Hawaiian lineages still deserve investigation, such as in the fern lineage. In this study, we address the question of the origin of the fern genus Ctenitis, which is present in the archipelago with two endemic species, Ctenitis squamigera and C. latifrons. Using a taxonomic sampling covering the pan-tropical distribution of the genus and three chloroplast DNA regions, we provide evidence that the genus in the Hawaiian Islands originated from a single long-distance dispersal from the Neotropics. This area is less represented than Asia and the South Pacific in the origin of Hawaiian ferns, but a Neotropical origin may be explained by the transportation of spores by tropical storms originating near Central America. Furthermore, the colonization of the Hawaiian Islands is estimated to have occurred between 4 [9-2] and 3 [7-1] mya. This timing is consistent with the ages of all main and extant islands of the archipelago, which already provided habitats for the establishment of the initial Ctenitis colonizer. In turn, this relatively late arrival to the islands and the related potentially low availability of ecological niches may have hampered diversification of the genus beyond the two extant species. ARTICLE HISTORY
... However, in particular, large invasive spiders, such as Dysderacrocata, use human-mediated transfer (Nedvěd et al. 2011), which may help increase the IRR of these species. Similar to angiosperms and vertebrates (except for birds), the successful expansion of pteridophytes worldwide is likely due to their high dispersal ability (linked to ferns producing numerous small spores that are easily transported over long distances and remain viable for several years ;Tryon 1970;Smith 1972;Wolf et al. 2001), while plants, in general, expand in great part because of horticulture, aquaculture (Reichard and White 2001) and aquarium trade (Peres et al. 2018). ...
Humans are facilitating the introduction and range expansion of invasive alien species (IAS), which have negatively impacted ecological and socio-economic systems worldwide. Understanding the global diffusion of IAS is important for developing environmental policies and management strategies. We estimate the rate of increase and the doubling times of the number of new records of 178 IAS using a global dataset with c. 3.4 million records obtained over c. 100 years. Here, we show that the number of records of IAS have exponentially increased with a mean double time of c. 14 years across the Earth. For the most analysed species, the number of records increased faster in the non-native than native continents, suggesting that such IAS might be exponentially expanding their range size. We also found that each continent has a taxonomic group with a particular increase in IAS records. Governments and scientists should pay attention to these taxonomic groups to implement appropriate control or management actions. Our study provides an indication that the current local, regional and continental efforts to control invasions may be not sufficient at the global scale. This is a concerning situation given the great number of areas available for invasion worldwide.
... Pteridophytes, including both lycophytes and ferns, are considered to be good climate indicators (Khine et al., 2019) because they are dispersed by spores which can travel thousands of kilometers by wind (Wolf et al., 2001), so that their distributions are more in equilibrium with climate than distributions of seed plants (Qian, 2009), and because the stomatal control of pteridophytes is less efficient than that of angiosperms (Brodribb & McAdam, 2011), so that they appear to be more susceptible to limited water availability . Across latitudinal gradients, species richness of pteridophytes generally decreases polewards (Karger et al., 2011), whereas on elevational gradients, species richness of pteridophytes commonly peaks at mid-elevations (Bhattarai et al., 2004;Khine et al., 2019;Tanaka & Sato, 2013;Tang et al., 2014). ...
There is a consensus that climate factors strongly influence species richness along elevation gradients, but which factors are crucial and how they operate are still elusive. Here, we assess the relative importance of temperature‐related versus precipitation‐related variables and the relative importance of extreme climate versus climate seasonality in driving pteridophyte species richness. We used correlation and regression analyses to relate species richness of pteridophytes, and their two major groups (lycophytes, ferns), in fifty 100‐m vertical bands to climatic factors representing different aspects of climatic conditions (general climate, stressful climate, and climate seasonality). Variation partitioning analysis was used to determine the relative importance of each group of climatic factors on species richness. Across the entire elevational gradient, species richness had a parabolic response to mean annual temperature (adjusted R2 = .87−.91), and a linear response to annual precipitation (adjusted R2 = .82). Mean annual temperature and annual precipitation in the second‐order polynomial model together explained 96.3%−98.7% of the variation in species richness. The variation in species richness uniquely explained by minimum temperature of the coldest month was much greater than that uniquely explained by temperature seasonality, but the variation in species richness uniquely explained by precipitation during the driest month was much smaller than that uniquely explained by precipitation seasonality. Overall, extreme climate variables explained slightly more variation than did climate seasonality. Our study suggests that pteridophyte richness along the elevational gradient is largely driven by a combination of both temperature‐ and precipitation‐related parameters, although precipitation‐related variables play a slightly stronger role, and that extreme low temperature events (at high elevations) and seasonal precipitation variability (at low elevations) are the strongest determinants of pteridophyte species richness. Relationships between elevation and species richness (a) or species density (b) for pteridophytes in Nepal. Each dot represents a 100‐m elevation band. Species density is defined as species richness in an elevational band being divided by the log10‐tranformed area (km2) of the elevational band.
... Given the prevalence of reproduction through spores, ferns in particular tend to be excellent dispersers and therefore are often believed to be more likely to occur whenever there are suitable conditions for their establishment and growth (although this notion has yet to be tested experimentally, Wild and Gagnon 2005). For instance, dispersal by wind in ferns and lycophytes can vary greatly between taxa but many species are known to have remarkable long-distance dispersal abilities (Barrington 1993;Wolf et al. 2001) and thus are often able to overcome geographical barriers more easily than other taxonomic groups (Tyron 1970). However, our understanding of how fern and lycophyte lineages evolved to occupy their current climatic niches is still incipient (Bystriakova et al. 2011;Hernandez-Rojas et al. 2021). ...
Honduran fern and lycophyte taxa under present and future climates. We found that species were distributed throughout most of the available climatic space. Under RCP2.6 and RCP8.5 projections 128 to 391 species will have their average niche positions outside of the predicted available climatic space by the years 2049-2099. Particularly affected will be species that grow in low temperature and high precipitation areas, which represent high altitude parks, such as Celaque National Park. Epiphytes showed smaller variance in their climatic niches than terrestrial species. However, terrestrial species showed higher loss in climate space (e.g., 82.9% vs. 17.1% for RCP8.5) and are more likely to be at risk in the future. In general, Hondu-ras is expected to become drier, with more extreme events of severe drought. Considering that ferns are particularly sensitive to changes in climate, if tested in the future, they could be used as a proxy for other Honduran plant taxa.
... In the aftermath of a fire event, most species die out and recolonization mediated by propagules from the surrounding landscape may be stochastic (Hubbell, 2001). Ferns can quickly colonize areas after extreme disturbance events such as fires, landslides, hurricanes and deforestation (Walker & Sharpe, 2010 and references therein) because of the high wind-dispersal capacity of its propagules, known as spores, which are both highly abundant and longlived (Perrie & Brownsey, 2007;Wolf et al., 2001). ...
Tropical forests have been rapidly deforested and degradation worldwide has outpaced biodiversity field sampling. No study to date has assessed the effects of insular habitats induced by hydroelectric dams on Amazonian understory plants. Fern community responses to anthropogenic effects on tropical forest islands can be revealed at a faster pace by using simple and cheap, yet informative, protocols that could be applied by non‐specialists.
This study seeks to both understand the drivers of fern and lycophytes assemblages on forest islands and investigate the relative costs and effectiveness of a simplified sampling protocol that can be applied by non‐specialists.
Fern species were sampled by a non‐specialist who photographed all ferns and lycophytes within seventeen 0.25‐ha plots on 10 forest islands at the lake of Balbina Hydroelectric dam, central Amazonia. Sampling was carried out opportunistically during a field expedition planned to conduct tree inventories. As predictors, we used locally measured or GIS‐derived descriptors of plot and landscape conditions. We used multivariate and linear models to further assess the influence of predictors on patterns of species richness and composition of ferns assemblages.
A total of 286 photographed individual ferns or lycophytes represented at least 23 species and 14 genera. The average number of taxa per plot was 6.1 in the islands and 14.3 in the mainland. The species pool found on islands was a nested subset of the mainland fern community. Species richness was positively related to island size and negatively related to isolation and fire severity. Area, isolation and fire severity also significantly explained variation in community composition.
The relative cost of the picture‐based fern protocol applied was very modest (only 4% of the total expedition budget), even compared to the typically low cost of alternative field campaigns.
We conclude that fern community structure in this forest archipelago was primarily driven by island size, isolation and fire disturbance. Moreover, we show that a simple sampling protocol carried out by a non‐specialist can lead to inexpensive and highly reliable ecological data. This opens an avenue for crowdsourcing ecological fern data collections using a citizen science approach.
... Ferns, which include about 12,000 species worldwide (Hassler, 2004e2021), are one of the oldest and the most species-rich groups of vascular plants (Mabberley, 2008;Qian et al., 2021a). Fern propagules are spores, which are small (usually <0.1 mm in equatorial axis and polar axis; Adsersen, 1995), and are capable of dispersing thousands of kilometers by wind (Wolf et al., 2001). Ferns are generally distributed broadly, and fern distributions are thought to be more in equilibrium with climate than most other groups of vascular plants (Qian, 2009). ...
Despite that several studies have shown that data derived from species lists generated from distribution occurrence records in the Global Biodiversity Information Facility (GBIF) are not appropriate for those ecological and biogeographic studies that require high sampling completeness, because species lists derived from GBIF are generally very incomplete, Suissa et al. (2021) generated fern species lists based on data with GBIF for 100 km × 100 km grid cells across the world, and used the data to determine fern diversity hotspots and species richness−climate relationships. We conduct an evaluation on the completeness of fern species lists derived from GBIF at the grid-cell scale and at a larger spatial scale, and determine whether fern data derived from GBIF are appropriate for studies on the relations of species composition and richness with climatic variables. We show that species sampling completeness of GBIF is low (<40%) for most of the grid cells examined, and such low sampling completeness can substantially bias the investigation of geographic and ecological patterns of species diversity and the identification of diversity hotspots. We conclude that fern species lists derived from GBIF are generally very incomplete across a wide range of spatial scales, and are not appropriate for studies that require data derived from species lists in high completeness. We present a map showing global patterns of fern species diversity based on complete or nearly complete regional fern species lists.
... Such old vicariance events are often invoked to explain disjunct amphi-oceanic distributions but actually rarely demonstrated in free-sporing tracheophytes (traditional 'pteridophytes') because of their high longdistance dispersal (LDD) ability due to their minute, numerous and light spores. In many recent studies, LDD seems to explain the majority of the disjunct and wide distributions in leptosporangiate ferns (as reviewed by Wolf, Schneider & Ranker, 2001;Haufler, 2007;Schaefer, 2011 (Labiak et al., 2014), Polystichum Roth (Le Péchon et al., 2016), Ctenitis (C.Chr.) C.Chr. , Rumohra Raddi (Bauret et al., 2017a) and grammitids (Bauret et al., 2017b). ...
The filmy fern genus Trichomanes mainly comprises Neotropical species and a few taxa in Africa and the western Indian Ocean. The aim of this study is to infer the phylogenetic placement of all five Afro-Malagasy taxa in the genus and to investigate their history via an expanded and dated phylogenetic analysis including 39 species representing over half the diversity of the genus. The results support the monophyly of Trichomanes including all the sampled species attributed to the genus, but also suggest the inclusion of the species Abrodictyum cellulosum, revealing a morphological diversity of the genus greater than what was traditionally recognized, and highlighting the importance of the campanulate sorus as a generic diagnostic character. To accommodate those new phylogenetic results and morphological investigations, we describe a new subgenus Afrotrichomanes grouping the Afro-Malagasy taxa (except T. crenatum). The dated history of the genus among the trichomanoids suggests at least two origins for the Palaeotropical species. A recent Cainozoic colonization from the Neotropics towards Africa gave rise to the West African taxon T. crenatum, and a possible Mesozoic vicariance event gave rise to subgenus Afrotrichomanes. The low species diversity of the genus in the Afro-Malagasy region is discussed.
... Many life-history traits of ferns, such as their unique life cycles with independent, often ephemeral gametophytes and relatively long-lived sporophytes, make it difficult to study one or more of these processes, such as mutation and selection, in these organisms. However, other traits, such as their ability to produce massive quantities of easily wind-dispersed spores (Wolf et al. 2001), make ferns ideal candidates for studying other processes, such as gene flow. ...
... Ferns and lycophytes (henceforth for simplicity called ferns) are a useful study group to assess biodiversity patterns because of their global distribution, contributing up to 70% of the species richness to local tropical floras, and because they have a reasonably high but manageable species richness (Kreft et al., 2010). In particular, being spore-dispersed reduces their dependence on biotic dispersal vectors, while enabling them to easily colonize suitable habitats, so that the confounding effects of dispersal limitation on assembly processes are reduced (Wolf et al., 2001;Karger et al., 2014). Previous studies on fern functional diversity along elevational gradients found that morphological trait diversity mirrors species richness patterns. ...
Functional traits determine how species interact with their abiotic and biotic environment. In turn, functional diversity describes how assemblages of species as a whole are adapted to their environment, which also determines how they might react to changing conditions. To fully understand functional diversity, it is fundamental to (a) disentangle the influences of environmental filtering and species richness from each other, (b) assess if the trait space saturates at high levels of species richness, and (c) understand how changes in species numbers affect the relative importance of the trait niche expansion and packing. In the present study, we determined functional diversity of fern assemblages by describing morphological traits related to resource acquisition along four tropical elevational transects with different environmental conditions and species richness. We used several functional diversity indices and their standardized effect size to consider different aspects of functional diversity. We contrasted these aspects of functional diversity with climate data and species richness using linear models and linear mixed models. Our results show that functional morphological trait diversity was primarily driven by species richness and only marginally by environmental conditions. Moreover, increasing species richness contributed progressively to packing of the morphological niche space, while at the same time decreasing morphological expansion until a saturation point was reached. Overall, our findings suggest that the density of co-occurring species is the fundamental driving force of morphological niche structure, and environmental conditions have only an indirect influence on fern resource acquisition strategies.
... Samples from P herbarium consulted online leave no doubts about the occurrence of H. hirsutum in Africa and the morphological proximity between this population and those of the Atlantic Forest, which is confirmed, in part, by the results of the phylogenetic analysis presented here. This is probably a successful case of long-distance dispersal (LDD), which is very common among ferns (Tryon 1970;Barrington 1993;Wolf et al. 2001). Del Rio et al. (2017 argue that events of LDD can explain disjunct distributions between Africa and America, which is the current distribution pattern for species of Hymenophyllum subg. ...
Sphaerocionium is the largest subgenus of Hymenophyllum and occurs mainly in tropical forests of the Neotropical Region. Species of Hymenophyllum occurring in Brazil are poorly known due to difficulties in species delimitation and the absence of detailed studies. The aim of the present study was to present a synopsis of Hymenophyllum subg. Sphaerocionium in the Atlantic Forest domain, based on molecular and morphological data. Field and herbarium specimens were morphologically analyzed by stereomicroscopy, optical microscopy, and scanning electron microscopy. Phylogenetic relationships were evaluated by sequence comparison of the plastidial regions trnG-R and rps4-trnS. Morphological and phylogenetic evidence led to the recognition of 14 taxa throughout the Atlantic Forest, five of which are endemic. The taxonomy and nomenclature of Hymenophyllum in Brazil are revised and 19 new lectotypifications are proposed. The conservation status and geographical distributions of all species are updated and a dichotomous key is provided. Resumo-Sphaerocionium representa o subgênero com maior riqueza florística dentro do gênero Hymenophyllum, e distribui-se principalmente nas florestas tropicais da região Neotropical. No Brasil, as espécies de Hymenophyllum ainda são pouco conhecidas, devidoà falta de estudos detalhados para delimitação dos táxons. Nosso objetivoé apresentar uma revisão das espécies de Hymenophyllum subg. Sphaerocionium ocorrentes no domínio da Floresta Atlântica brasileira, baseada em dados morfológicos e moleculares. Para tanto, amostras de campo e de herbários foram analisadas morfologicamente através de estereomicroscopia, microscopiaóptica e microscopia eletrônica de varredura. As relações filogenéticas entre as espécies foram testadas através da análise das regiões plastidiais trnG-R e rps4-trnS. As evidências morfológicas e moleculares permitiram o reconhecimento de 14 espécies para o domínio da Floresta Atlântica, cinco delas endêmicas. Uma revisão taxonômica e nomenclatural está sendo apresentada, na qual são propostas 19 novas lectotipificações. Nós atualizamos o status de conservação e o padrão de distribuição geográfico para todas as espécies. Uma chave dicotômica para a identificação das mesmas tambémé apresentada.
... Such water-dependency for sexual reproduction, together with poor stomatal control and low water-use efficiency (Weigand et al. 2020), may explain why fern diversity increases more strongly along gradients of water availability and peaks in humid tropical mountains (Moran 2008;. Still, ferns are ubiquitous across the globe, which has been attributed in part to the lightness of their spores and their consequent ability to disperse over very long distances (Tryon 1986;Wolf et al. 2001;Moran 2008). Indeed, this remarkable vagility may result in low rates of local endemism ) and therefore biogeographic areas of limited lineage specificity. ...
Biogeographic regions have been extensively used as reference units in macroecological studies and to prioritize biodiversity conservation efforts. However, classical bioregionalizations were delineated based on taxonomical similarity across space, and thus the importance of historical factors may have been underrated. This limitation may be particularly relevant for lineages with long and complex evolutionary histories, such as ferns. Here, we drew on an exhaustive distribution dataset including all fern species and subspecies of Europe (661 grid-cells of c. 110 × 110 km each), as well as a nearly complete molecular phylogeny to define fern phyloregions based on their phylogenetic relatedness. Also, we quantified the degree of specificity of individual phylogenetic clades to the phyloregions using a new index of geographical confinement based on phylogenetic diversity. Six distinct phyloregions were identified, with a primary divide between north-eastern and south-western Europe. Both phylogenetic beta diversity and clade specificity were overall low, supporting the idea that dispersal limitation is not a major driver of fern distribution. Yet, the phylogenetic specificity analysis revealed that ancient fern lineages show preference for northern latitudes, which explained the northeast to southwest split of the territory. More than 40 years after the only bioregionalization analysis for the European fern flora, our study provides a fresh regional delineation that takes into account the evolutionary history of the group. In addition to classical bioregionalization approaches, our phylogenetic specificity index allowed us to elucidate the identity of the clades that ultimately shaped the bioregions, which might otherwise had remained obscure.
... Such water-dependency for sexual reproduction, together with poor stomatal control and low water-use efficiency (Weigand et al. 2020), may explain why fern diversity increases more strongly along gradients of water availability and peaks in humid tropical mountains (Moran 2008;. Still, ferns are ubiquitous across the globe, which has been attributed in part to the lightness of their spores and their consequent ability to disperse over very long distances (Tryon 1986;Wolf et al. 2001;Moran 2008). Indeed, this remarkable vagility may result in low rates of local endemism ) and therefore biogeographic areas of limited lineage specificity. ...
Climate change is a major driver of biodiversity decline with pervasive effects in biodiversity hotspots, where many endemic and threatened species thrive. However, the biological drivers of extinction susceptibility remain largely elusive, which hampers the implementation of effective conservation policies. Here, we advocate for the use of phylogenies as a complementary tool to inform policy makers. If we assume that the traits that determine extinction susceptibility are somewhat evolutionarily conserved, identifying the clades that accumulate a disproportionate amount of threatened species may help to mitigate potential increases in extinction risk among currently unthreatened species in these clades, even if the underlying biological drivers are unknown. We focused on the complete endemic angiosperm flora of a Mediterranean hotpot (Iberian Peninsula) to examine phylogenetic patterns in extinction risk expressed as IUCN categories (Least Concern “LC”, Near Threatened “NT”, Vulnerable “VU”, Endangered “EN” and Critically Endangered “CR”) using alpha and beta diversity metrics, comparative methods and a “hot node” approach. Phylogenetic diversity was significantly low for EN species and marginally significant for NT and CR, while LC and VU categories showed random pattern. Phylogenetic beta diversity (PBD) between IUCN categories was intermediate (0.40 – 0.61) and predominantly due to the “true” turnover component of PBD. Phylogenetic turnover was significantly low between NT – VU and VU – EN, suggesting that closely related species tend to show different threat status. In contrast, the comparisons involving the CR category sit toward the higher tail of the distribution, indicating a somewhat higher degree of clade specificity for CR species. In line with these patterns, phylogenetic signal in extinction risk was rather low (lambda = 0.23). Several of the “hot” clades that accumulated a significantly high number of species with the same threat status were specific to certain IUCN categories, yet few of them were observed across the categories. Most notably, the Caryophyllales stood out as the main threat-accumulating lineage, particularly within the Plumbaginaceae. All in all, our results indicate that few phylogenetic clades concentrate a great fraction of the extinction-risk gradient in the endemic flora of the western Mediterranean, and monitoring programs should pay particular attention to these extinction-prone lineages.
... Spore dispersal by wind, rather than vicariance events, is known to be an important feature driving fern species demography (Wolf et al. 2001), and several cases of long-range dispersal at intercontinental scales are documented for the worldwide B. lunaria species complex (Dauphin et al. 2017;Farrar and Stensvold 2017). Nevertheless, our analysis of gene flow among Swiss B. lunaria populations indicates that spore dispersal is not without limitations, even at relatively short distances. ...
... Most spores are dispersed by wind (Tryon 1970(Tryon , 1986. The distance that spores travel varies by release height and wind velocity: for short-statured terrestrial ferns, the vast majority of spores disperse < 2 m; for taller ferns it is up to 100 m in closed forest conditions, and in open environments up to a couple of kilometres (Raynor et al. 1976;Moar et al. 2011;Rose & Dassler 2017), and a small percentage are dispersed much greater distances (Wolf et al. 2001). ...
... The present study is the first case of the East-West differentiation pattern in fern species in the Japanese archipelago. The scarcity of this differentiation pattern in ferns may reflect the high dispersal ability of ferns that have small spores as propagules [77], or merely that few phylogenetic studies have been conducted on Japanese ferns so far. The phylogeographic studies on Japanese plants concluded that such a geographic genetic structure would be caused by climatic changes during repeated glacial periods in the Quaternary period. ...
Although polyploidy is pervasive and its evolutionary significance has been recognized, it remains unclear how newly formed polyploid species become established. In particular, the impact of multiple origins on genetic differentiation among populations of a polyploid species and whether lineages of independent origins have different evolutionary potentials remain open questions. We used population genetic and phylogenetic approaches to identify genetic differentiation between lineages with independent origins within an allotetraploid fern, Lepisorus nigripes. A total of 352 individuals from 51 populations were collected throughout the distribution range. To examine the genetic structure, multilocus genotyping, Bayesian population structure analysis, and neighbor-net analysis were carried out using single-copy nuclear genes. Phylogenetic trees were constructed to detect recurrent polyploid origins. Proportions of abortive spores were analysed as the measure of postzygotic reproductive isolation. Two genetically distinct lineages, the East-type and the West-type, were distributed mainly in the eastern and western parts, respectively, of the Japanese archipelago. Phylogenetic analyses indicated independent origins of these types and detected additional independent origins within each type. We also revealed limited genetic recombination between both types, even in their sympatric regions. F1 hybrids between the East- and West-types showed a reduction in fertility. It is likely that the East- and West-types formed independently in the eastern and western parts of Japan, respectively. The limited genetic recombination and reduced fertility of hybrids suggest that the two types are at an incipient stage of speciation. Two polyploid lineages with independent geographic origins could develop reproductive isolation barrier(s).
... Genetic analyses of disjunct populations from a number of species, such as Pinus nigra in western Europe, have highlighted the role of LGM refugia in postglacial colonization (e.g., Afzal-Rafii & Dodd, 2007). These analyses also revealed complex postglacial population dynamics, uncovering the interplay between refugial persistence and long-distance migration (Escudero, Valcárcel, Vargas, & Luceño, 2010;Fernandez, Hu, Gavin, de Lafontaine, & Heath, 2020;Wolf, Schneider, & Ranker, 2001). For example, although refugial populations of Thuja plicata persisted through the LGM in the interior of the Pacific Northwest, long-distance immigrants from coastal populations dominated the interior range expansion during the postglacial period (Fernandez et al., 2020). ...
Abstract Larix laricina (eastern larch, tamarack) is a transcontinental North American conifer with a prominent disjunction in the Yukon isolating the Alaskan distribution from the rest of its range. We investigate whether in situ persistence during the last glacial maximum (LGM) or long‐distance postglacial migration from south of the ice sheets resulted in the modern‐day Alaskan distribution. We analyzed variation in three chloroplast DNA regions of 840 trees from a total of 69 populations (24 new sampling sites situated on both sides of the Yukon range disjunction pooled with 45 populations from a published source) and conducted ensemble species distribution modeling (SDM) throughout Canada and United States to hindcast the potential range of L. laricina during the LGM. We uncovered the genetic signature of a long‐term isolation of larch populations in Alaska, identifying three endemic chlorotypes and low levels of genetic diversity. Range‐wide analysis across North America revealed the presence of a distinct Alaskan lineage. Postglacial gene flow across the Yukon divide was unidirectional, from Alaska toward previously glaciated Canadian regions, and with no evidence of immigration into Alaska. Hindcast SDM indicates one of the broadest areas of past climate suitability for L. laricina existed in central Alaska, suggesting possible in situ persistence of larch in Alaska during the LGM. Our results provide the first unambiguous evidence for the long‐term isolation of L. laricina in Alaska that extends beyond the last glacial period and into the present interglacial period. The lack of gene flow into Alaska along with the overall probability of larch occurrence in Alaska being currently lower than during the LGM suggests that modern‐day Alaskan larch populations are isolated climate relicts of broader glacial distributions, and so are particularly vulnerable to current warming trends.
... They assume different patterns of coverage, occurrence or non-occurrence, which results in the floristic heterogeneity and the peculiar composition of each site, even in spatially close areas, corroborating with studies by Rodrigues and Nave (2000), Carvalho et al. (2005) and Mallmann et al. (2016). In addition, in the specific case of ferns and lycophytes, floristic dissimilarity is influenced by intrinsic factors, such as spores dispersion (Jones et al. 2006), which occurs close to mother plants (Wolf et al. 2001) or vegetative (Jones et al. 2007), restricting their distribution to short distances (less than 100 m) on a regional scale (Jones et al. 2006). ...
Riparian forests present biotic and abiotic factors that influence environmental dissimilarity, which reflect specific fern distribution. The purpose of this this study, was to evaluate the environmental heterogeneity associated to the terrestrial fern communities in riparian forest remnants in the grasslands southern half of Rio Grande do Sul state . We sampled ten 5×5m plots in each site (AI, AII and AIII), totaling 30 plots. In each plot, fern species were inventoried and vegetative, microclimatic and edaphic parameters were collected. A total of 24 species were surveyed in the three riparian forest remnants, distributed in 19 genera and 10 families. The Principal Components Analysis (PCA) showed that plots of AI had the highest temperature and aluminum values, while humidity was the lowest, which was reflected in the decrease of ferns richness. Soil moisture and air humidity, were variables more related to the plots of AII and AII, indicating that these plants were favored in these environments. The floristic identity characteristic of each site suggests that many species are dependent to certain local environmental conditions. In this sense, even in very geographically close sites, riparian remnants deserve conservation attention, since they are capable of harboring high diversity in this grassland physiognomy in southern Brazil. The results of this integrated study, with vegetation, climatic, and edaphic parameters, suggest, as expected, that ferns categorically respond to the heterogeneity shown by riparian environments, even when fragments are geographically very close to each other.
... In fact, both fragments constituted a single unit in the past and are currently threatened by the same activities. The genetic exchange between fragments should be enough to consider a single subpopulation if we consider the high dispersal capacity of ferns, whose spores are capable of traveling hundreds of kilometers (Wolf et al., 2001). ...
Re-finding and conservation status of the threatened fern Maxonia apiifolia (Dryopteridaceae) in Southern Havana wetland, Cuba Re-localización y estado de conservación del helecho amenazado Maxonia apiifolia (Dryopteridaceae) en el humedal sur de La Habana, Cuba www.revistas.geotech.cu/index.php/abc A S RAC The re-finding and conservation status of the endangered fern Maxonia apiifolia in Southern Havana are reported. We estimated the extent of occurrence of M. apiifolia by GPS marking. We registered the number of mature individuals, their reproductive status and phorophyte species. Maxonia apiifolia was found in two swamp forest fragments located in La Luisa, Melena del Sur (Mayabeque), named Embarcadero and Los Patos. Together these areas represent 4.30 km 2 for the species' extent of occurrence, comprising a single location and a single subpopulation distributed between the two forest fragments. We counted a number of 64 mature individuals (23% with fertile fronds) of M. apiifolia. Roystonea regia, Callophyllum antillanum and Calyptronoma occidentalis were the most frequent phorophytes. La Luisa constitutes a significant site for M. apiifolia conservation, because it contains one of the biggest subpopulations compared with the ones recently found. Its abundance, high number of mature individuals observed and estimated and its generalist condition in terms of phorophyte preference suggest that this subpopulation has a good conservation status. R SU N Se reportó la re-localización y estado de conservación del helecho amenazado Maxonia apiifolia en el sur de La Habana. Se estimó la extensión de presencia de la especie a través del marcaje con GPS. Se registró el número de individuos maduros, su estado reproductivo y la especie forófito. Maxonia apiifolia fue encontrada en dos fragmentos de bosque de ciénaga localizados en el poblado La Luisa, Melena del Sur (Mayabeque) nombrados Embarcadero y Los Patos. Ambas áreas representan 4.30 km² para la extensión de presencia de la especie, y constituyen una sola localidad y una sola subpoblación distribuida entre los dos fragmentos de bosque. Se contaron 64 individuos maduros de M. apiifolia (23% con frondes fértiles). Roystonea regia, Callophyllum antillanum y Calyptronoma occidentalis fueron las especies de forófitos más frecuentes. La Luisa constituye un sitio importante para la conservación de M. apiifolia, porque contiene una de las subpoblaciones más grandes hasta ahora reportadas. Su abundancia, alto número de individuos maduros observados y su condición de generalista en cuanto a la preferencia de forófito, sugieren que esta subpoblación tiene un buen estado de conservación. * Autor para correspondencia:
The geographical distribution of a taxon is the result of factors specific to the organisms and the environment in which they live. Similar, repetitive, and non-random occurrence arrangements comprise the distribution patterns. Ferns are a group with a wide range, whose spatial patterns are often associated with spore dispersion and environmental factors. Pteridaceae is the most species-rich fern family in Brazil, present in all phytogeographic Brazilian domains. This study aimed to map the occurrence of all Pteridaceae species in Brazil to verify distribution patterns. The occurrence points of the species were obtained from the review of herbaria, and the patterns were delimited according to the congruence of the limits of species presence, and the range in Brazilian states and the biogeographical provinces. Each taxon’s range was classified as continuous and disjunct; for the first one, some subtypes were also considered: very restricted, restricted, moderately wide, and wide. The presence of 205 species was verified, with natural occurrences for Brazil. Minas Gerais and Rio de Janeiro are the richest states in the number of species, and regarding the provinces, the Atlantic and Paraná Forests are the richest. A total of 123 patterns were defined, 93 (173 species) for continuous, and 30 for disjunct (32 species). Considering the continuous patterns, 18 were classified as very restricted (70 species), 14 as restricted (27 species), 51 as moderately wide (63 species), and 10 as wide (13 species). The Brazilian mountain regions are home to a large number of endemic species (such as Serra do Mar, Serra da Mantiqueira, and the Guiana Shield). Environmental characteristics, such as rock types, humidity, precipitation, and elevation seem to be important for the species’ establishment. Furthermore, the dispersal ability of the spores must be considered, given the range of occurrence of the taxa and the age of the lineages.
Intercontinental disjunct distributions can arise either from vicariance, from long-distance dispersal, or through extinction of an ancestral population with a broader distribution. Tectariaceae s.l., a clade of ferns in Polypodiales with ca. 300 species mainly distributed in the tropics and subtropics, provide an excellent opportunity to investigate global distribution patterns. Here, we assembled a dataset of eight plastid markers and one nuclear marker of 636 (92% increase of the earlier largest sampling) accessions representing ca. 210 species of all eight genera in Tectariaceae s.l. (Arthropteridaceae, Pteridryaceae, and Tectariaceae s.s.) and 35 species of other families of eupolypods Ⅰ. A new phylogeny is reconstructed to study the biogeography and trait-associated diversification. Our major results include: (1) a distinct lineage of Tectaria sister to the rest of the American Tectaria is identified; (2) Tectariaceae s.l., and the three families: Arthropteridaceae (Arthropteris), Pteridryaceae (Draconopteris, Malaifilix, Polydictyum, Pteridrys), and Tectariaceae s.s. (Hypoderris, Tectaria, and Triplophyllum), might have all originated in late Cretaceous; (3) only five intercontinental dispersals occurred in Pteridryaceae and Tectariaceae s.s. giving rise to their current intercontinental disjunction; (4) we provide the second evidence in ferns that a long-distance dispersal between Malesia and Americas during the Paleocene to Eocene led to the establishment/origin of a new genus (Draconopteris); and (5) diversification rate of each state of leaf dissection is different, and the lowest is in the simple-leaved taxa.
This datasheet on Christella dentata covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Impacts, Uses, Prevention/Control, Further Information.
Ferns are an integral part of the world's flora, appreciated for their beauty as ornamentals, problematic as invaders and endangered by human interference. They often dominate forest understories but also colonize open areas, invade waterways and survive in nutrient-poor wastelands and eroded pastures. Presented here is the first comprehensive summary of fern ecology, with worldwide examples from Siberia to the islands of Hawaii. Topics include a brief history of the ecological study of ferns, a global survey of fern biogeography, fern population dynamics, the role of ferns in ecosystem nutrient cycles, their adaptations to xeric environments and future directions in fern ecology. Fully illustrated concepts and processes provide a framework for future research and utilization of ferns for graduate students and professionals in ecology, conservation and land management.
Ferns are an integral part of the world's flora, appreciated for their beauty as ornamentals, problematic as invaders and endangered by human interference. They often dominate forest understories but also colonize open areas, invade waterways and survive in nutrient-poor wastelands and eroded pastures. Presented here is the first comprehensive summary of fern ecology, with worldwide examples from Siberia to the islands of Hawaii. Topics include a brief history of the ecological study of ferns, a global survey of fern biogeography, fern population dynamics, the role of ferns in ecosystem nutrient cycles, their adaptations to xeric environments and future directions in fern ecology. Fully illustrated concepts and processes provide a framework for future research and utilization of ferns for graduate students and professionals in ecology, conservation and land management.
Premise:
Historical biogeography of ferns is typically expected to be dominated by long-distance dispersal, due to their minuscule spores. However, few studies have inferred the historical biogeography of a large and widely distributed group of ferns to test this hypothesis. Our aims are to determine the extent to which long-distance dispersal vs. vicariance have shaped the history of the fern family Blechnaceae, to explore ecological correlates of dispersal and diversification, and to determine whether these patterns differ between the northern and southern hemispheres.
Methods:
We used sequence data for three chloroplast loci to infer a time-calibrated phylogeny for 154 out of 265 species of Blechnaceae, including representatives of all genera in the family. This tree was used to conduct ancestral range reconstruction and stochastic character mapping, estimate diversification rates, and identify ecological correlates of diversification.
Key results:
Blechnaceae originated in Eurasia and began diversifying in the late Cretaceous. A lineage comprising most extant diversity diversified principally in the austral Pacific region around the Paleocene-Eocene Thermal Maximum. Land connections that existed near the poles during periods of warm climates likely facilitated migration of several lineages, with subsequent climate-mediated vicariance shaping current distributions. Long-distance dispersal is frequent and asymmetrical, with New Zealand/Pacific Islands, Australia, and tropical America being major source areas.
Conclusions:
Ancient vicariance and extensive long-distance dispersal have shaped the history of Blechnaceae in both the northern and southern hemispheres. The exceptional diversity in austral regions appears to reflect rapid speciation in these areas; mechanisms underlying this evolutionary success remain uncertain. This article is protected by copyright. All rights reserved.
Temporal variation of airborne fern spore concentrations in Bratislava during the three years (2019‒2021) was studied using a Hirst-type aerospore sampler. Fern spores were frequently present in the air but at low concentrations. The total annual spore concentration recorded was 523 spores/m³, belonging to eight spore types of fern plants (Asplenium sp., Athyrium sp., Botrychium sp., Cystopteris sp., Dryopteris sp., Matteuccia struthiopteris and Polypodium sp. of ferns and Equisetum sp. of horsetails). The taxa contributing the highest spore concentration were Dryopteris (52% of the total; mean value for the three analysed years) and Athyrium (26% of the total). Species of these two genera are abundant in the fragments of natural woodland within the city. The season period from July to August shows the most intense airborne spore dispersal process in each analysed year. Although the average daily spore concentration did not exceed 1 spore/m³ during the period analysed, we recorded values of up to 15 spores/m³ on several days. Since fern spores are one of the allergenic airborne bioparticles, it is assumed that their inhalation at this concentration may already induce inhalation allergy symptoms in sensitive individuals. The relationships between selected weather variables and mean daily fern spore concentrations for Dryopteris and Athyrium were evaluated through Spearman’s correlation test. The spore concentrations were positively associated with air temperature and/or sunshine and negatively with relative air humidity.
The Amotape-Huancabamba Zone, straddling the Huancabamba Depression in the tropical Andes, is often recognized as a major hotspot of species richness for plants and animals in the Neotropics. The biogeographic role of the area as a barrier, transition, or unique endemism zone in the Andes has long been debated. Here, using tree ferns, we take a new look at this question and discuss the biogeographic significance and limits of the Amotape-Huancabamba Zone. We find that tree fern distribution supports the idea that the Amotape-Huancabamba zone is a unique biogeographic unit within the Andes defined by high endemism, overlap of the floras of the Northern and Central Andes, and high overall species richness; however, the centrally located Huancabamba-Marañón depression plays only a minor role as a floristic barrier.
Background
Despite the broad distribution of several species in Gleicheniaceae in the neotropical region, Diplopterygium is the only genus having a restricted distribution. Species of Gleicheniaceae occupy open (including anthropogenic) habitats and produce large amounts of wind-dispersed propagules – so why does Diplopterygium bancroftii, the only neotropical species in the genus, have a restricted distribution?
Aims
We investigated if the restricted distribution of Diplopterygium in the Neotropics reflected the absence of suitable areas for the establishment.
Methods
We used species distribution modeling to identify suitability areas during different periods of the Pleistocene (Last Glacial Maximum and Last Interglacial), the Holocene, and the present.
Results
The environmental suitability model at the present time corroborated the current distribution of D. bancroftii, and also evidenced additional suitable potential areas where the species has so far not been recorded, especially in eastern Brazil. In projections of the past, no connectivity was observed between suitable areas in the Andes and eastern Brazil.
Conclusions
As neither the dispersal ability nor the absence of suitable areas at the present time or in the past were limiting factors to the range expansion of Diplopterygium, we discuss possible migration barriers and propose a hypothesis for its colonization history in the Neotropics.
Neoblechnum brasiliense (Blechnaceae) is common and widespread in South America but has been known from Mesoamerica by only one collection from Guatemala by Julian Steyermark in 1939. We discovered two new occurrences of the species, in Belize and Mexico, extending the range of the species over 1000 km north and west into northern Mesoamerica. We discuss possible explanations for the rarity of the species in Mesoamerica and its disjunction from South America.
The research analyzed the population structure and spatial distribution pattern of individuals of two populations of Cyathea delgadii Sternb. (Cyatheaceae), occurring in Cerrado areas in the state of Maranhão/Brazil. The study areas are located in the East of Maranhão, in the Milagre village, municipality of Matões and in the Pedras Village in the municipality of São João do Sóter. In each area, seven contiguous plots of 30m x 10m (300m²) with 20m inter distribution between plots. Were sampled in the unitsall the individuals of C. delgadii, with height of the living caudex and diameter at the ground level (DNS). The height of the sampled individuals was distributed in classes and for analysis of the spatial distribution , the Morisita index and the variance/average ratio calculation were used. The statistical significance was verified through the Chi-squared. Were sampled 120 and 39 individuals in 100% and 90% of the plots in the Milagre and Pedras Villages, respectively, mostly in the first height classes (> 0-0,8m and> 0,8-1,6m). The distribution pattern of the two populations of Cyathea delgadiiwas aggregated with statistical significance. With the results are inferred some biotic and abiotic factors that can influence the distribut ion of Cyathea delgadiiin its habitat and construction of its population niche. The data presented in the research made it possible to aggregate basic information for the management and preservation of this species in the Brazilian Northeast, contributing to the population knowledge of arborescent ferns.
Cambridge Core - Plant Sciences - Evolution in Isolation - by Kevin C. Burns
We present a phylogenetic analysis of the moss genus Daltonia based on nucleotide sequences from three plastid loci (psbT, trnL, trnG) plus the nuclear ribosomal RNA gene (ITS), including 9 of 21 species in this genus. Of the nine species, seven are well–supported as monophyletic, even when multiple accessions came from different continents. Early diverging species in the genus have relatively restricted ranges that are limited to a single continent, whereas most or all later–diverging species have broad intercontinental distributions. The observation that intercontinental distributions are repeated in multiple monophyletic species suggests that a key innovation underlying enhanced abilities for long dispersal evolved within Daltonia, and that this potential was inherited among derived species from their common ancestor. The nature of this (these) innovation(s) remains obscure, but may be related to both relaxation of ecological limitations on establishment, and to effective dispersal of spores per se.
The taxonomic status of certain Pteridium (bracken) populations in Britain and their relationships with other British populations and with North American taxa, are much disputed. Apart from the common Pteridium aquilinum subsp. aquilinum var. aquilinum these other British populations have been variously treated as as either subsp. latiusculum (Tryon's var. latiusculum), as a separate species P. pinetorum, or as hybrids between British var. aquilinum and North American latiusculum.
In an attempt to infer evolutionary relationships among these taxa, we sequenced several regions of the chloroplast genome, including the genes rbcL, atpB, and rps4, in addition to the spacer regions between rbcL and atpB, and between atpB and atpE. We sampled from specimens representing six bracken taxa and seven populations from both Britain and North America. Specimens from Britain were chosen from aquilinum, fulvum, and pinetorum. North American taxa were represented by latiusculum (2 populations), pseudocaudatum, and pubescens. Following alignment, sequences were subjected to phylogenetic analysis.
Abstract-Three quantitative cladistic biogeographic methods, namely, component analysis, Brooks parsimony analysis (BPA), and three-area statements (TAS) have been proposed for obtaining general area cladograms from taxon-area cladograms. Available programs implementing these methods include COMPONENT versions 1.5 and 2.0 for component analysis, TAS for three-area statements, and Hennig86 for analysing matrices for both three-area statements and BPA. Ten different data sets were analysed with these programs and items of error were used to evaluate the general area cladograms obtained. None of the computer implementations of the methods compared proved to be more effective than the others. "...all methodologies, even the most obvious ones, have their limits...". Feyerabend (1993:231).
We analyzed nucleotide variation in rbcL (the gene encoding the large subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase) from 99 genera of leptosporangiate ferns representing 31 of the 33 extant families. Phylogenetic relationships were inferred using three methods: neighbor joining, maximum parsimony, and maximum likelihood. All three methods resulted in optimal trees that were similar. Within the context of those taxa examined, these trees suggest that: 1) Polypodiaceae, Grammitidaceae and Pleurosoriopsis form a monophyletic group that is most derived among indusiate ferns; 2) Davallia is closely related to the Polypodiaceae; 3) Tectaria is related to Oleandraceae rather than to other members of Dryopteridaceae; 4) Rumohra and Elaphoglossum are closely related; 5) Dryopteridaceae are polyphyletic; 6) a monophyletic group consists of Polypodiaceae, Grammitidaceae, Davalliaceae, Oleandraceae, Nephrolepidaceae, Lomariopsidaceae, Dryopteridaceae, Thelypteridaceae, Blechnaceae, Aspleniaceae, and Pleurosoriopsis; 7) Dennstaedtiaceae, Monachosoraceae, Pteridaceae, Vittariaceae, and the previous clade form a monophyletic group; 8) Dennstaedtiaceae are polyphyletic; 9) tree ferns in the Cyatheaceae, Metaxyaceae, and Dicksoniaceae form a monophyletic group that emerged early in the diversification of leptosporangiate ferns; 10) Plagiogyriaceae and Loxomataceae emerge with the tree ferns; 11) heterosporous water ferns form a monophyletic group that diverged prior to the tree ferns; 12) Schizaeaceae, Cheiropleuriaceae, Dipteridaceae, Gleicheniaceae, Matoniaceae, and Hymenophyllaceae are basal to the heterosporous aquatic ferns; and 13) Osmundaceae are the most basal lineage of the leptosporangiate ferns.
We present the first cladistic analysis of extant ferns based on morphological characters. Our data set consisted of 77 vegetative and reproductive morphological/anatomical characters recorded on a broad sampling of 50 extant pteridophyte taxa, with representatives of all major fern groups, and one seed plant (Cycas). An annotated list of both retained and excluded morphological characters is presented. Results from the morphological analysis are compared with an independent analysis of rbcL data carried out here for the same set of pteridophyte taxa. Finally, we analyze a combined (morphological and molecular) data set. All three data sets were analyzed using maximum parsimony. Two separate sets of analyses using different taxon combinations were conducted on each of the three data sets. Analysis 1 focused on phylogenetic relationships of ferns only (Filicopsida, Botrychium, and Angiopteris), using Cycas as an outgroup representative from the seed plants. Analysis 2 focused on phylogenetic relationships of pteridophytes (Filicopsida, Angiopteris, Botrychium, Equisetum, Psilotum), using Lycopodium as the outgroup. In both sets of analyses, the combined data set provided the most robustly supported hypothesis of relationships. Results from the combined data set in Analysis 1 provided strong bootstrap support for the monophyly of the following clades: leptosporangiate ferns (with Osmunda as the most basal leptosporangiate fern), heterosporous ferns, Cheiropleuria-Dipteris, Diplopterygium-Stromatopteris, tree ferns, schizaeoid ferns, pteridoid ferns, and a large clade consisting of a derived group of leptosporangiate ferns that excludes dennstaedtioids and pteridoids. Various smaller clades within some of these larger clades also have strong support. The dennstaedtioid ferns are paraphyletic. We use the results of the combined data set in Analysis 1 to examine character evolution within the leptosporangiate ferns. Results from the combined data set in Analysis 2 indicated robust support for essentially the same fern clades as the combined data set in Analysis 1. In both Analyses 1 and 2, bootstrap support for the leptosporangiate fern clade is much greater using the combined data set than when either the morphological or, particularly, the molecular data set is analyzed separately. Relationships among major groups of pteridophytes at the base of the tree (Botrychium, Angiopteris, Psilotum, Equisetum, Lycopodium) were poorly supported by the combined data in Analysis 2, except for a weak association between Botrychium and Psilotum. We are convinced from this study of the value of using both molecular and morphological data sets in combination as well as separately. A synthetic approach that integrates paleobotanical and neobotanical data will be of greatest interest in further elucidating the phylogenetic relationships of pteridophytes.
The life history biology of the fern Lorinseria areolata was studied at three sites adjacent to the Escambia River, Florida, which represented part of its habitat diversity in the Gulf Coastal Plain. Site 1 was dominated by Pinus elliottii and was flooded only during hurricanes. Site 2 was dominated by Magnolia virginiana and Gordonia lasianthus and was flooded for 3–5 months of the year. Site 3 was dominated by Nyssa sylvatica var. biflora and Taxodium distichum and was flooded for 9–12 months of the year. Lorinseria areolata coverage was 92, 61, and 16% of total understory at sites 1, 2, and 3. Rhizome length varied 5-fold between sites. Microtopography varied little at site 1. Microtopography at sites 2 and 3 consisted of distinctive hummocks and hollows. Association analysis documented that L. areolata was distributed randomly with regard to microtopography at site 1, and was strongly associated with hummocks at sites 2 and 3. Seven life history classes (LHCs) for L. areolata were discriminated based on field collections and seasonal observations over three years. Density of LHCs decreased logarithmically, with the exception of older LHCs whose age could not be determined beyond 30 months. Spore storage in dead erect sporophylls allowed the establishment of gametophytes throughout the year. Up to 25% of the gametophyte population survived the cold and relative drought of winter. More than half of field collected gametophytes were small males, and up to a third were larger bisexual gametophytes. Safe sites for completion of the life cycle were limited to decayed pine stumps and twigs at site 1, and to hummocks at sites 2 and 3. It was hypothesized that the acidifying action of Pinus elliottii litter on soil contributed to the abundance of Lorinseria areolata at site 1, and that parts of the microhabitat mosaic at sites 2 and 3 which most closely approached edaphic characteristics of site 1 provided safe sites for the fern.
Populations of a fern gametophyte presumed to be of the genus Vittaria occur commonly in the uplands of the southeastern United States. The gametophytes occur on non-calcareous rock outcrops of various composition in areas which provide continuous moisture and protection from temperature extremes. Gametophytes in these habitats are robust and long lived, frequently forming the dominant vegetation in areas covering several square feet. Reproduction is exclusively vegetative by production of gemmae. Although sex organs are present in most populations, viable sporophytes are never produced. The gametophytes have previously been considered most likely to be V. lineata, which occurs in Florida, but morphological and physiological comparisons do not support that conclusion. Significant differences between Appalachian and Florida gametophytes occur in growth form, growth rate, cold hardiness, sporophyte production, and patterns of gemma production. The distribution of the Appalachian gametophytes correlates with old, unglaciated land masses suggesting antiquity rather than recent introduction. Present evidence favors the interpretation that the Appalachian Vittaria gametophytes either belong to a tropical American species from which they have long been separated, or that they represent a distinct species of which the sporophyte no longer exists.
The extreme isolation and mid-Pacific origin of the Hawaiian archipelago has ensured that all indigenous organisms have arrived via long-distance dispersal or have evolved from successfully colonizing species. Although this isolation has also produced high rates of species endemism in angiosperms (89% or more), that rate in pteridophytes is considerably less (76%). The ratio of native species to the estimated number of original successful colonizing species in angiosperms (3.4) is more than double that for pteridophytes (1.6). One possible explanation for the lower speciation rate in pteridophytes is that populations of these species are more likely to experience interpopulational gene flow because of the great vagility of their wind-dispersed spores. We conducted isozymic surveys of populations from the island of Hawaii of the indigenous allotetraploid species Asplenium adiantum-nigrum, putatively derived from two strictly European diploid taxa. Our data support multiple hybrid origins for the populations surveyed, with a minimum of 3, and possibly as many as 17, discrete hybridization events having produced the genetic diversity observed. Since the parental taxa are not found in Hawaii, each hybrid lineage must have arrived in the archipelago independently of the others. Similar long-distance, repeated dispersal events may be occurring between insular and noninsular populations of other native pteridophytes in Hawaii and in other insular regions of the world, thus contributing to the relatively low rates of speciation and insular endemism in this ancient group of plants.
A largely tropical family of six mostly epiphytic genera that are restricted either to the New World or the Old World, except for Antrophyum and Vittaria, which are widely distributed in both regions. The spores are mostly trilete but are either tri- or monolete in Vittaria and Antrophyum. The sporoderm consists of a blechnoid type of exospore and a thin perispore of one or two layers, usually plain or papillate with globules or rodlets.
Chlorophyll-bearing spores occur in only a few unrelated families and genera in the Pteridophyta, including Equisetaceae, Osmundaceae, Grammitidaceae, Hymenophyllaceae, Blechnum (B. nudum), Lomariopsis sorbifolia, and all species of Christiopteris, Marginariopsis, Matteuccia. Onoclea, and Onocleopsis. These spores germinate in less than three days (mean=1.46 days) and have viability lengths of one year or less (mean=48 days). Non-chlorophyll-bearing spores occur in the majority of ferns, require longer periods for germination (4-210 days; mean=9.5 days), and have longer viabilities (mean=1045 days). Gametophytes from green spores also appear to develop more rapidly than those from non-green spores. It is suggested that rapid germination and relatively short viability of green spores is due to their constant respiration and apparent lack of dormancy. Species with green spores occur consistently in wet mesophytic habitats, and it is suggested that lack of selective pressure for dormancy has maintained this condition in Equisetaceae and Osmundaceae. In the other groups of ferns, the condition is most likely derived.
The percentage of pantropical and amphioceanic genera of ferns far exceeds similar percentages for angiosperms. Conversely, the number of "endemic" fern genera is much lower than the comparable figure for flowering plants. Comparison of the two groups of plants on islands points out even more strikingly the lower percentages of generic and specific endemism of ferns. These distributional differences cannot be accounted for by the longer geologic history of ferns, but can be attributed to their greater dispersibility. The wider distribution of ferns, together with the absence of many of the speciation barriers operative in angiosperms, has contributed to a relatively slower rate of speciation in the ferns, and probably also to a lower extinction rate. Delimitation of generic and suprageneric taxa is therefore more difficult in many cases.
Whereas the distribution of the principal pteridophyte families over the major parts of the globe is quite similar to that of the principal angiosperm families, pteridophyte genera are in general considerably more widespread. Four possible explanations are discussed: greater age of fern genera and thus a longer period available for dispersal; slower evolution of ferns; greater dispersability through small size of diaspores; and non-equivalence of fern and angiosperm genera. Furthermore, primitive fern genera diverge in their distribution patterns from those of primitive angiospersm; they tend to occupy special habitats and/or to possess special growth forms, rather than being concentrated in geographical relict areas, as are angiosperms. Finally, the 'American Paradox' in the distribution of fern genera and sections, which is an imbalance between the Old and the New World, is briefly alluded to.
New data on floral conditions and pollination mechanisms in the Hawaiian angiosperm flora are presented and analyzed statistically in order to suggest probable explanations for the high degree of dioecism, wind-pollination, species polymorphism, and other features which characterize the floras of oceanic islands, or other waif floras. The Hawaiian flora is nearly definitive because it is relatively old (although all volcanic islands are geologically comparatively young), diversified over varied topography, ecologically rich, provided with sufficient land area for development and maintenance of adaptive radiation and its products, and strongly isolated from source areas. The Juan Fernandez Islands offer useful comparisons because they are relatively old and ecologically rich, although they are smaller and much less isolated than the Hawaiian Islands. New Zealand is extremely ancient as an island, and perhaps has always been one. Its great isolation in age compensates in expression of insular phenomena for its somewhat lesser isolation in space, being relatively near Australian and Indo-Malaysian source areas. Similar evolutionary expressions should be expected in these three island groups, with deviations related to geographical and geological differences among the three. Other oceanic islands (Canary Islands, St. Helena, Mauritius, Samoa, Society Islands) will be expected to show the phenomena discussed here to a lesser extent. Angiosperms brought to an oceanic island by aerial (chiefly bird) dispersal are distinctive in being (1) a strongly disharmonic group compared with continental floras, and (2) removed, in the insular situation, from any genetic contact with parent populations. The consequences of these two characteristics are the development of distinctive genetic and floral patterns. The evolutionary curriculum of the aerially dispersed angiosperms is best fulfilled on relatively large islands, such as New Zealand and the Hawaiian chain. On such islands, aerially dispersed angiosperms will be expected to radiate as a consequence of available ecological niches coupled with the paucity of immigrants. This would be expected to lead to speciation-as it does-but these species fail to develop strong sterility barriers. High value of heterozygosity in the insular situation dictates that subdivision into smaller groups, each with less heterozygosity than the whole, will be deleterious. Moreover, geographical and ecological barriers, rather than genetic ones, maintain the integrity of species on islands. To be sure, the island floras considered here are mostly woody in character, and lack of sterility barriers among species groups is typical of woody plants in continental as well as insular localities. Nevertheless this characteristic of woody species, in addition to their suitability to mild maritime climates, may make them successful as long-term island residents. Without sterility barriers, occasional events of hybridization can circulate the genetic content of a species complex, compensating for the fact that mainland populations are prevented by isolation from contributing to the gene pool. This results in maintaining genetic variability; it also results in species polymorphism, a feature notoriously characteristic of islands. Speciation on islands will be aided by development of distinctive ecological preferences, precinctiveness (e.g., seed gigantism or loss of a former means of dispersal), self-pollination, and extinction of intermediate forms. At the species level, maintenance of genetic variability to a maximal extent will tend to prevent extinction. This is achieved by various devices which enforce or promote outcrossing. These conditions include dioecism, gynodioecism, monoecism, andromonoecism, gynomonoecism, polygamodioecism, polygamomonoecism, dichogamy, and anemophily. The frequency of these conditions is much higher on the Hawaiian Islands and other major oceanic islands than on continental areas. All of these outcrossing devices could potentially circulate genetic material actively. In island populations, consisting of relatively few individuals, such devices could promote as high level of heterozygosity as relatively slow rates of outcrossing in mainland populations with relatively large numbers of individuals. The value of devices which promote outcrossing is sufficiently great that immigrants which possess them establish on islands despite increased dispersal requirements: dioecious species must be introduced as at least a pair of seeds which establish simultaneously. This has occurred in the Hawaiian flora in at least 10 genera, such as Astelia, which is dioecious in non-Hawaiian as well as Hawaiian species. In other cases, dioecism in Hawaiian genera has probably or conceivably been evolved autochthonously. Autogamous and monoclinous species may be advantaged for initial establishment in insular situations, but the long-term advantages of species which can achieve outcrossing by some mechanism, or in which hybrid complexes can be formed, or in which both characteristics are present or can be developed, seem to override the reproductive advantages of exclusive autogamy. Exogamous species or complexes may be expected over long periods of time to outlive the autogamous immigrants, unless the latter can be reintroduced. If land areas are relatively small or new, exogamous complexes are not present or cannot be developed, and the above considerations will apply to a much smaller extent. Just as anemophily is a feature of floral biology related to outcrossing, so are other floral features related to the "insular syndrome" of evolutionary tendencies. In the Hawaiian, New Zealand, and Juan Fernandez floras, entomophilous flowers are notably small and odorless; white, green, and yellow are the predominant colors. These features seem related to the nature (small body size, etc.) of the insular insects faunas. Congestion of inconspicuous flowers is a tendency which may compensate and tend to insure pollination.
Botanists disagree about the relationship of the serpentine and the woodland members of the Adiantum pedatum complex in eastern North America. Whereas some recognize the two taxa as subspecies, others judge variation to be strictly ecophenic. In the present investigation, starch gel electrophoresis, cytology, and multivariate morphometric analysis were used to elucidate the systematic relationship of these two diploid taxa. Populations of the serpentine and the woodland maidenhair fern are quite divergent genetically. Seven alleles are unique to the serpentine taxon, and genetic identities between populations of the two taxa are low (Ī = 0.495). This value is comparable to those for pairs of congeneric species in other groups of ferns, and particularly low compared to genetic identities for angiosperm species. Patterns of variation in morphological characters of A. pedatum reflect the genetic divergence between the diploid taxa: the taxa are well separated in a discriminant analysis, but no single character is diagnostic. A taxon of tetraploid maidenhair ferns discovered in the study is apparently the polyploid derivative of a hybrid between the serpentine and the woodland maidenhair ferns, as demonstrated by its electrophoretic phenotype. Non-segregation of alleles in gametophyte progeny of the tetraploid indicates that little pairing occurs between the two progenitor genomes. Recent origin of the tetraploid is suggested by several of its attributes: presence of multivalents at meiosis, duplicated gene loci, and restricted geographic range.
Ferns are especially useful for the study of certain biogeographic problems of migration and speciation because the species have a high and nearly equivalent capacity for spore dispersal by air transport. Dispersal can bring spores of many species to an island from a source area; the ones that become established are not a random assortment of the source species. Island floras have a major element of widely distributed source area species, although these are a minor element in the source area. The endemics on islands are mostly related to narrowly distributed source species, although these are a minor element in the island flora. In an archipelago the endemics are nearly always related to source species rather than to other species of the insular flora. Establishment of a species on an island is an individual, rather than a population, phenomenon because dispersal cannot bring the variability of a source population to the island. Adaptability of the genotype-phenotype of the single spore to a new environment and sensitivity to selection are characteristics that dominate success in migration and evolutionary potential under geographic isolation. Widely and narrowly distributed source species differ in these characteristics, and these differences account for the relative proportions of the two source groups in the insular flora and their relations to insular endemics. Re-immigration can maintain gene-flow between islands and is a deterrent to the evolution of species-flocks in an archipelago.
Biogeographical inferences depend on, but must also be used to construct, classifications. In practice, we apply a knowledge of biogeographical principles or tendencies, established through weight of examples from many organisms, to questions of relationship. These principles state that taxonomic affinity is often correlated with or predicted by geographic proximity, similar ecological needs, climatological affinity and historical or geological factors. Certain phenomena, such as glaciation and continental drift, have resulted in repetitive distribution patterns. We also apply a knowledge of fern biology when evaluating distributional data. For example, because dispersal of spores is generally greater than of seeds, fern genera and species tend to be more widely distributed and show less endemism than seed plant taxa. Toxonomic gaps caused by extinctions may be less noticeable in ferns.
A local fern flora consists of species with a variety of systematic and chorological relationships. Thus the biogeography of a flora is a composite of species-specific biogeographies. However, large-scale environmental changes effect the biogeography of a flora as a whole. The eastern Asian-eastern North American disjunct distribution pattern in some recently revised fern taxa may have arisen by a layering of many climatic and geological events. The fern flora of Seram Island, east Malesia, is most closely related to New Guinea. Together with geological evidence, this suggests that the Seram fern flora originated largely by dispersal from New Guinea. From the systematic relationship of Taenitis, it is assumed that the present distribution pattern of the genus has been primarily caused by westward dispersal with allopatric or parapatric speciation in Malesia. In the cladistic biogeography of Drynarioideae and Pyrrosia both dispersal and vicariance were assumed to have been involved. As molecular approaches have been initiated in the systematics and biogeography of ferns, usefulness of the method is stressed.
Vegetative reproduction by the gametophyte generation has allowed a number of fern species to persist beyond their normal geographic range. In at least two of these, Trichomanes and Vittaria in the eastern United States, the sporophyte stage of the life cycle has been eliminated completely, perhaps for ten million years or more. Despite this long period of reliance on vegetative reproduction, genetic diversity in the Appalachian Vittaria gametophytes, as measured by starch gel enzyme electrophoresis, remains comparable to that of sexual plants, although it is largely partitioned into monomorphic populations. Widely separated populations are not particularly divergent; the taxon as a whole appears equally as cohesive as sexual species, suggesting that factors other than gene flow are responsible for long term maintenance of species integrity. The Appalachian Vittaria gametophytes and similarly derived taxa merit recognition as distinct species.
Synopsis
The most common kinds of speciation result in new species that initially have a small range. These will develop a limited or an extensive range depending upon the geographic extent of the environment to which they are adapted. A significant element in the extent of the potential range of a new species is the adaptation inherited from the parental species. Selection of a parental species for a local environment at one site can lead to a narrow ecological adaptation and often to a limited potential range. These species are likely to produce derived ones that also have a limited range, and these derivates will increase the regional species endemism and diversity. Selection of a parental species for migration to other sites can lead to a broader ecological adaptation and often to a broad potential range. These species are more likely to produce derived ones that also have an extensive range, and these derivates will increase regional species diversity.
The extreme isolation and mid-Pacific origin of the Hawaiian archipelago has ensured that all indigenous organisms have arrived via long-distance dispersal or have evolved from successfully colonizing species. Although this isolation has also produced high rates of species endemism in angiosperms (89% or more), that rate in pteridophytes is considerably less (76%). The ratio of native species to the estimated number of original successful colonizing species in angiosperms (3.4) is more than double that for pteridophytes (1.6). One possible explanation for the lower speciation rate in pteridophytes is that populations of these species are more likely to experience interpopulational gene flow because of the great vagility of their wind-dispersed spores. We conducted isozymic surveys of populations from the island of Hawaii of the indigenous allotetraploid species Asplenium adiantum-nigrum, putatively derived from two strictly European diploid taxa. Our data support multiple hybrid origins for the populations surveyed, with a minimum of 3, and possibly as many as 17, discrete hybridization events having produced the genetic diversity observed. Since the parental taxa are not found in Hawaii, each hybrid lineage must have arrived in the archipelago independently of the others. Similar long-distance, repeated dispersal events may be occurring between insular and noninsular populations of other native pteridophytes in Hawaii and in other insular regions of the world, thus contributing to the relatively low rates of speciation and insular endemism in this ancient group of plants.
By the Escambia River, Florida, the acidifying action of Pinus elliottii litter on soil contributed to the abundance of Lorinseria areolata at site 1, and parts of the microhabitat mosaic at sites 2 and 3 which most closely approached edaphic characteristics of site 1 provided safe sites for the fern. -from Authors
Because of the homothallic nature of many pteridophytes, two categories of mating are possible: intragametophytic selling (the origin of both gametes from a single gametophyte) and inter-gametophytic mating (the origin of each gamete from a different gametophyte).Various morphological and genetical criteria (placement of the gametangia on the thallus, their sequence of ontogeny, the capacity for simple polyembryony and genetic self-incompatibility) can be used to indicate the relative probability of intragametophytic selfing or intergametophytic mating. Only the former has genetic significance (i.e.complete homozygosity); if the latter is evidenced, then detailed studies of population variability are required to ascertain the breeding system.
Three types of reproductive systems involve the gametophyte generation: intragametophytic selfing, intergametophytic mating and apogamy. Apogamy generally offers the shortest gametophyte generation and the least evolutionary potential, intergametophytic mating systems generally have the longest gametophyte generation and the greatest evolutionary potential, and intragametophytic mating systems are intermediate in both respectS. It is envisioned that the interaction between gametophyte ecology and evolutionary potential is important in the evolution of a taxon's reproductive system.
Quantification in historical biogeography has usually been based on the search for a single branching relationship among areas of endemism. Unlike organisms, however, areas rarely have a unique hierarchical history. Dispersal barriers appear and disappear and may have different effects on different species. As a result, the biota of an area may consist of several components with separate histories, each of which may be reticulate rather than branching. In an attempt to address these problems, I present a new biogeographic method, dispersal-vicariance analysis, which reconstructs the ancestral distributions in a given phylogeny without any prior assumptions about the form of area relationships. A three-dimensional step matrix based on a simple biogeographic model is used in the reconstruction. Speciation is assumed to subdivide the ranges of widespread species into vicariant components; the optimal ancestral distributions are those that minimize the number of implied dispersal and extinction events. Exact algorithms that find the optimal reconstruction(s) are described. In addition to their use in taxon biogeography, the inferred distribution histories of individual groups serve as a basis for the study of general patterns in historical biogeography, particularly if the relative age of the nodes in the source cladograms is known.
Solitary plants of Asplenium platyneuron occur disjunctively on recently produced coal spoils in southern Iowa. They are assumed to have been produced by self-fertilization of isolated gametophytes and therefore highly homozygous. Cultures of isolated and paired gametophytes originating from these solitary sporophytes produced second-generation sporophytes with 89 and 93% success, respectively, indicating a low genetic load as expected. The failure of gametophytes from coal-spoil plants to produce sporophytes with even greater success may result from homoeologous chromosome pairing and recombination at meiosis which allows production of variable spores and expression of genetic load from plants produced by self-fertilization of single gametophytes. Cultures of isolated and paired gametophytes originating from sporophytes in populations central to the species' range produced second-generation sporophytes with 83 and 90% success, respectively, indicating a significantly greater genetic load in populations but still a relatively low genetic load for the species. Through low genetic load, regularity of sporophyte production from isolated gametophytes, and ability of such plants to release variability through homoeologous chromosome pairing, Asplenium platyneuron is remarkably adapted for, and successful in, colonizing distant habitats through long-range spore dispersal.