Genetic drift or natural selection? Hybridization and asymmetric mitochondrial introgression in two Caribbean lizards (Anolis pulchellus and Anolis krugi)

Hybridization and gene introgression can occur frequently between closely related taxa, but appear to be rare phenomena among members of the species‐rich West Indian radiation of Anolis lizards. We investigated the pattern and possible mechanism of introgression between two sister species from Puerto Rico, Anolis pulchellus and Anolis krugi, using mitochondrial (ND2) and nuclear (DNAH3, NKTR) DNA sequences. Our findings demonstrated extensive introgression of A. krugi mtDNA (k‐mtDNA) into the genome of A. pulchellus in western Puerto Rico, to the extent that k‐mtDNA has mostly or completely replaced the native mtDNA of A. pulchellus on this part of the island. We proposed two not mutually exclusive scenarios to account for the interspecific matings between A. pulchellus and A. krugi. We inferred that hybridization events occurred independently in several populations, and determined that k‐mtDNA haplotypes harboured in individuals of A. pulchellus can be assigned to four of the five major mtDNA clades of A. krugi. Further, the spatial distribution of k‐mtDNA clades in the two species is largely congruent. Based on this evidence, we concluded that natural selection was the probable driving mechanism for the extensive k‐mtDNA introgression into A. pulchellus. Our two nuclear data sets yielded different results. DNAH3 showed reciprocal monophyly of A. pulchellus and A. krugi, indicating no effect of hybridization on this marker. In contrast, the two species shared nine NKTR alleles, probably due to incomplete lineage sorting. Our study system will provide an excellent opportunity to experimentally assess the behavioural and ecological mechanisms that can lead to hybridization in closely related taxa.     

Climate as a driver of tropical insular diversity: comparative phylogeography of two ecologically distinctive frogs in Puerto Rico

The effects of late Quaternary climate on distributions and evolutionary dynamics of insular species are poorly understood in most tropical archipelagoes. We used ecological niche models under past and current climate to derive hypotheses regarding how stable climatic conditions shaped genetic diversity in two ecologically distinctive frogs in Puerto Rico. Whereas the mountain coquí Eleutherodactylus portoricensis is restricted to montane forest in the Cayey and Luquillo Mountains, the red‐eyed coquí E. antillensis is a habitat generalist distributed across the entire Puerto Rican Bank (Puerto Rico and the Virgin Islands, excluding St Croix). To test our hypotheses, we conducted phylogeographic and population genetic analyses based on mitochondrial and nuclear loci of each species across their range in Puerto Rico. Patterns of population differentiation in E. portoricensis, but not in E. antillensis, supported our hypotheses. For E. portoricensis, these patterns include: individuals isolated by long‐term unsuitable climate in the Río Grande de Loíza Basin in eastern Puerto Rico belong to different genetic clusters; past and current climate strongly predicted genetic differentiation; and Cayey and Luquillo Mountains populations split prior to the last interglacial. For E. antillensis, these patterns include: genetic clusters did not fully correspond to predicted long‐term unsuitable climate; and past and current climate weakly predicted patterns of genetic differentiation. Genetic signatures in E. antillensis are consistent with a recent range expansion into western Puerto Rico, possibly resulting from climate change and anthropogenic influences. As predicted, regions with a large area of long‐term suitable climate were associated with higher genetic diversity in both species, suggesting larger and more stable populations. Finally, we discussed the implications of our findings for developing evidence‐based management decisions for E. portoricensis, a taxon of special concern. Our findings illustrate the role of persistent suitable climatic conditions in promoting the persistence and diversification of tropical island organisms.     

Deep intra‐island divergence of a montane forest endemic: phylogeography of the Puerto Rican frog Eleutherodactylus portoricensis (Anura: Eleutherodactylidae)

Aim Hypotheses proposed for lineage diversification of tropical montane species have rarely been tested within oceanic islands. Our goal was to understand how basin barriers and Pleistocene climatic fluctuations shaped the distribution of diversity in Eleutherodactylus portoricensis (Eleutherodactylidae), a frog endemic to the montane rain forests of Puerto Rico. Location The north‐eastern (Luquillo) and south‐eastern (Cayey) mountains of Puerto Rico. Methods We generated mitochondrial DNA (mtDNA) control region sequences (c. 565 bp) from 144 individuals of E. portoricensis representing 16 localities, and sequenced 646 bp of cytochrome b and 596 bp of nuclear DNA (nDNA) rhodopsin exon and intron 1 from a subset of individuals. We conducted a phylogenetic analysis on the mtDNA sequence data and explored population substructure with maximum parsimony networks, a spatial analysis of molecular variance, and pairwise F_ST analysis. Coalescent simulations were performed to test alternative models of population divergence in response to late Pleistocene interglacial periods. Historical demography was assessed through coalescent analyses and Bayesian skyline plots. Results We found: (1) two highly divergent groups associated with the disjunct Luquillo and Cayey Mountains, respectively; (2) a shallow mtDNA genetic discontinuity across the La Plata Basin within the Cayey Mountains; (3) phylogeographic congruence between nDNA and mtDNA markers; (4) divergence dates for both mtDNA and nDNA pre‐dating the Holocene interglacial (c. 10 ka), and nDNA suggesting divergence in the penultimate interglacial (c. 245 ka); and (5) historical demographic stability in both lineages. Main conclusions The low‐elevation Caguas Basin is a long‐term barrier to gene flow between the two montane frog populations. Measures of genetic diversity for mtDNA were similar in both lineages, but lower nDNA diversity in the Luquillo Mountains lineage suggests infrequent dispersal between the two mountain ranges and colonization by a low‐diversity founder population. Population divergence began prior to the Holocene interglacial. Stable population sizes over time indicate a lack of demonstrable demographic response to climatic changes during the last glacial period. This study highlights the importance of topographic complexity in promoting within‐island vicariant speciation in the Greater Antilles, and indicates long‐term persistence and lineage diversification despite late Pleistocene climatic oscillations.     

Biogeographic barriers in south‐eastern Australia drive phylogeographic divergence in the garden skink,Lampropholis guichenoti

Aim To investigate the impact of climatic oscillations and recognized biogeographic barriers on the evolutionary history of the garden skink (Lampropholis guichenoti), a common and widespread vertebrate in south‐eastern Australia. Location South‐eastern Australia. Methods Sequence data were obtained from the ND4 mitochondrial gene for 123 individuals from 64 populations across the entire distribution of the garden skink. A range of phylogenetic (maximum likelihood, Bayesian) and phylogeographic analyses (genetic diversity, Tajima’s D, Φ_ST, mismatch distribution) were conducted to examine the evolutionary history and diversification of the garden skink. Results A deep phylogeographic break (c. 14%), estimated to have occurred in the mid–late Miocene, was found between ‘northern’ and ‘southern’ populations across the Hunter Valley in northern New South Wales. Divergences among the geographically structured clades within the ‘northern’ (five clades) and ‘southern’ (seven clades) lineages occurred during the Pliocene, with the location of the major breaks corresponding to the recognized biogeographic barriers in south‐eastern Australia. Main conclusions Climatic fluctuations and the presence of several elevational and habitat barriers in south‐eastern Australia appear to be responsible for the diversification of the garden skink over the last 10 Myr. Further molecular and morphological work will be required to determine whether the two genetic lineages represent distinct species.     

Sea level,topography and island diversity: phylogeography of the Puerto Rican Red‐eyed Coquí, Eleutherodactylus antillensis

Quaternary climatic oscillations caused changes in sea level that altered the size, number and degree of isolation of islands, particularly in land‐bridge archipelagoes. Elucidating the demographic effects of these oscillations increases our understanding of the role of climate change in shaping evolutionary processes in archipelagoes. The Puerto Rican Bank (PRB) (Puerto Rico and the Eastern Islands, which comprise Vieques, Culebra, the Virgin Islands and associated islets) in the eastern Caribbean Sea periodically coalesced during glaciations and fragmented during interglacial periods of the quaternary. To explore population‐level consequences of sea level changes, we studied the phylogeography of the frog Eleutherodactylus antillensis across the archipelago. We tested hypotheses encompassing vicariance and dispersal narratives by sequencing mtDNA (c. 552 bp) of 285 individuals from 58 localities, and four nuDNA introns (totalling c. 1633 bp) from 173 of these individuals. We found low support for a hypothesis of divergence of the Eastern Islands populations prior to the start of the penultimate interglacial c. 250 kya, and higher support for a hypothesis of colonization of the Eastern Islands from sources in eastern Puerto Rico during the penultimate and last glacial period, when a land bridge united the PRB. The Río Grande de Loíza Basin in eastern Puerto Rico delineates a phylogeographic break. Haplotypes shared between the PRB and St. Croix (an island c. 105 km south‐east of this archipelago) likely represent human‐mediated introductions. Our findings illustrate how varying degrees of connectivity and isolation influence the evolution of tropical island organisms.     

Saurian malaria in the Caribbean: Plasmodium azurophilum sp. nov., a malarial parasite with schizogony and gametogony in both red and white blood cells

A survey of 466 Caribbean lizards found Plasmodium parasites present in Anolis species only of five islands. Parasites presently considered to be P. floridense occurred on Grand Cayman, North Bimini, Jamaica, Hispaniola (Haiti), and Puerto Rico. A second species, P. azurophilum, is described as new from Anolis cybotes of Haiti, A. krugi of Puerto Rico, and A. lineatopus and A. grahami of Jamaica. It lacks visible pigment in erythrocytic host cells but can produce it occasionally. Both asexual and sexual forms occur in a variety of white blood cells, notably in azurophil granulocytes and polymorphonuclear leucocytes. Experimental infections indicate that the leucocytic phase occurs after the acute erythrocytic infection declines, thus suggesting that the schizogonic and gametogonic cycles in white cells may represent an adaptive defense against immune mechanisms of the host. Mean numbers of nuclei in schizonts and mean gametocyte size are influenced by host species and type of host cell.     

Phylogeography of the parthenogenic ant Platythyrea punctata: highly successful colonization of the West Indies by a poor disperser

Aim We investigated the spatio‐temporal patterns of genetic diversity in West Indian and mainland populations of a widespread parthenogenic ant (Platythyrea punctata F. Smith) to infer source populations and subsequent colonizations across its geographic range. Location Central America, Texas and the West Indies (Florida, the Bahamas, Greater and Lesser Antilles). Methods We employed phylogeographic reconstruction based on 1451 bp of mitochondrial DNA (cytochrome c oxidase subunits I and II) sequenced from 91 individuals of P. punctata. We employed standard population genetic analyses, Bayesian phylogenetic analyses, haplotype networks and molecular dating methods as performed by beast . We also employed phylogenetic analysis using two nuclear markers (970 bp) to understand the placement of P. punctata in the globally distributed genus Platythyrea. Results Based on highly reduced haplotypic variation and temporal estimates, rapid expansion and dispersal from Central America best explains the observed distribution of haplotypes. Platythyrea punctata successfully invaded the West Indies very few times. One haplotype occurred on every island surveyed from the Bahamas and Florida in the north to Barbados at the southern edge of its range. Haplotype diversity in the West Indies is quite low, despite a larger sample size relative to the mainland. Most mainland colonies collected each possessed a unique haplotype, whereas only Florida and the larger islands (the Dominican Republic, Puerto Rico and Guadeloupe) contained more than one haplotype. Island haplotypes were most similar to haplotypes collected in northern Mexico and southern Texas, but genetic distances were nevertheless high. The putative sister species of P. punctata appears to be an endemic of Hispaniola (P. strenua Wheeler & Mann), even though older, mainland populations of P. punctata are sympatric with at least two other congenerics. Main conclusions Dispersal seems very limited on the mainland, with well‐defined clades corresponding to geographical regions. Colonization of the islands from the mainland was extremely rare, but once successful there were very few barriers to expansion to nearly every island in the West Indies. We hypothesize that this invasion occurred during the late Pleistocene as the climate became warmer and less arid.     

Multilocus phylogeography of a widespread savanna–woodland‐adapted rodent reveals the influence of Pleistocene geomorphology and climate change in Africa's Zambezi region

Understanding historical influences of climate and physiographic barriers in shaping patterns of biodiversity remains limited for many regions of the world. For mammals of continental Africa, phylogeographic studies, particularly for West African lineages, implicate both geographic barriers and climate oscillations in shaping small mammal diversity. In contrast, studies for southern African species have revealed conflicting phylogenetic patterns for how mammalian lineages respond to both climate change and geologic events such as river formation, especially during the Pleistocene. However, these studies were often biased by limited geographic sampling or exclusively focused on large‐bodied taxa. We exploited the broad southern African distribution of a savanna–woodland‐adapted African rodent, Gerbilliscus leucogaster (bushveld gerbil) and generated mitochondrial, autosomal and sex chromosome data to quantify regional signatures of climatic and vicariant biogeographic phenomena. Results indicate the most recent common ancestor for all G. leucogaster lineages occurred during the early Pleistocene. We documented six divergent mitochondrial lineages that diverged ~0.270–0.100 mya, each of which was geographically isolated during periods characterized by alterations to the course of the Zambezi River and its tributaries as well as regional ‘megadroughts’. Results demonstrate the presence of a widespread lineage exhibiting demographic expansion ~0.065–0.035 mya, a time that coincides with savanna–woodland expansion across southern Africa. A multilocus autosomal perspective revealed the influence of the Kafue River as a current barrier to gene flow and regions of secondary contact among divergent mitochondrial lineages. Our results demonstrate the importance of both climatic fluctuations and physiographic vicariance in shaping the distribution of southern African biodiversity.     

Fat frogs,mobile genes: unexpected phylogeographic patterns for the ornate chorus frog (Pseudacris ornata)

The southeastern coastal plain of the United States is a region marked by extraordinary phylogeographic congruence that is frequently attributed to the changing sea levels that occurred during the glacial‐interglacial cycles of the Pleistocene epoch. A phylogeographic break corresponding to the Apalachicola River has been suggested for many species studied to date that are endemic to this region. Here, we used this pattern of phylogeographic congruence to develop and test explicit hypotheses about the genetic structure in the ornate chorus frog (Pseudacris ornata). Using 1299 bp of mtDNA sequence and seven nuclear microsatellite markers in 13 natural populations of P. ornata, we found three clades corresponding to geographically distinct regions; one spans the Apalachicola River (Southern Clade), one encompasses Georgia and South Carolina (Central Clade) and a third comprises more northerly individuals (Northern Clade). However, it does not appear that typical phylogeographic barriers demarcate these clades. Instead, isolation by distance across the range of the entire species explained the pattern of genetic variation that we observed. We propose that P. ornata was historically widespread in the southeastern United States, and that a balance between genetic drift and migration was the root of the genetic divergence among populations. Additionally, we investigated fine‐scale patterns of genetic structure and found the spatial scale at which there was significant genetic structure varied among the regions studied. Furthermore, we discuss our results in light of other phylogeographic studies of southeastern coastal plain organisms and in relation to amphibian conservation and management.     

Phylogeographic structure and regional history of Lemniscomys striatus (Rodentia: Muridae) in tropical Africa

Aim This study aims to elucidate the phylogeography of the murid rodent Lemniscomys striatus and to evaluate the relative roles of ecological change, habitat patchiness, rivers and geological barriers in structuring patterns of diversity. Location Sub‐Saharan Africa. Methods The extent of phylogeographic patterns and molecular genetic diversity (cytochrome b gene) were addressed in a survey of 128 individuals of L. striatus from 42 localities. Using maximum parsimony, maximum likelihood, Bayesian, network and genetic structure analyses, we inferred intraspecific relationships and tested hypotheses for historical patterns of gene flow within L. striatus. Results Our results identified four major geographical clades within L. striatus: a West African clade, a Benin‐Nigeria clade, a Central African clade, and an East African clade. Several subclades were identified within these four major clades. Restricted gene flow with isolation by distance was recorded, which is congruent with the low dispersal ability of such a small murid rodent. No clear signal of population expansion was detected within clades or subclades. Main conclusions The western rift system and the Volta and Niger rivers may have acted as long‐term extrinsic barriers to gene flow, resulting in the emergence of the four main clades of L. striatus. The observed pattern of mitochondrial variation observed within each clade probably results from late Pleistocene climatic and vegetation changes: during adverse conditions (forest expansion), L. striatus may have survived only in refugia, and then experienced range expansion under favourable conditions (savanna expansion).     

Phylogeography of the giant wood spider (Nephila pilipes, Araneae) from Asian–Australian regions

Aim There are currently few population genetic studies on widely distributed SE Asian terrestrial organisms. We have studied the genetic diversification pattern of the giant wood spider, Nephila pilipes (Araneae: Tetragnathidae) to see whether fluctuations in rain forest extents generated by Quaternary climatic changes left signatures on populations of this agile terrestrial arthropod. Location The collecting localities were distributed in the following seven regions: (1) N Australia; (2) India (Calcutta, Karziranga and Sukna); (3) SE Asia (N Vietnam, Malaysia, Singapore and Bali); (4) SE China (Fujian, Guandong, Hong Kong and Hainan); (5) SW China (Guangxi and Yunnan); (6) E Asian islands (Ryukyu islands and Taiwan); and (7) the Philippine Islands. Methods A total of 374 specimens were collected from the East Asian continent and islands, SE Asia, India, and northern Australia. Mitochondrial cytochrome oxidase I gene partial sequences were used as the molecular marker to infer the phylogeographic diversification patterns. Results From the specimens collected, 67 haplotypes were identified, which could be grouped into five major clades. The dominant clade contained populations in regions ranging from Okinawa to Bali (spanning a distance of more than 4000 km), but their genetic variations were not structured and were not significantly associated with geographical distances. Three clades contained specimens collected from peripheral regions of the distribution range of N. pilipes, such as India, N Australia, and NE Asia. Members of the clade distributed in NE Asia were sympatric but those of the clades distributed in Australia and India were allopatric with those of the dominant clade. Main conclusions The results of this study indicate that, during Quaternary glacial periods, the rain forests in SE Asia might have been more or less continuous and thus generated an unstructured genetic diversification pattern of N. pilipes inhabiting this region. However, during such periods, populations in peripheral regions such as India, N Australia and NE Asia might have been isolated in refugia, thus accounting for the observed genetic divergence from populations in the SE Asian region.     

Extensive intraspecific genetic diversity of a freshwater crayfish in a biodiversity hotspot

1. The freshwater crayfish Cherax dispar (Decapoda: Parastacidae) inhabits coastal regions and islands of South East Queensland, Australia. We hypothesised that populations of C. dispar on different islands would be more genetically divergent from each other than populations from different drainages within the same island or on the mainland. 2. Phylogenetic and phylogeographic analyses were conducted on two mitochondrial genes (cytochrome oxidase subunit I & 16S ribosomal DNA) and one nuclear gene (Internal Transcribed Spacer region 2). Phylogeographic patterns were compared with those for other freshwater organisms in the area. 3. Deep genetic divergences were found within C. dispar, including four highly divergent (up to 20%) clades. The geographic distribution of each of the clades revealed strong latitudinal structuring along the coast rather than structuring among the islands. The high genetic divergence observed among the C. dispar clades was estimated to have pre‐dated island formation and may represent ancient river drainage patterns. 4. A restricted distribution was observed for the most divergent clade, which was discovered only on two of the sand islands (North Stradbroke Island and Moreton Island). Furthermore, strong phylogeographic structuring was observed within this clade on North Stradbroke Island, where no haplotypes were shared between samples from opposite sides of the island. This low connectivity within the island supports the idea that C. dispar rarely disperse terrestrially (i.e. across watersheds).     

Leopard tortoises in southern Africa have greater genetic diversity in the north than in the south (Testudinidae)

In contrast to mammals, little is known about the phylogeographic structuring of widely distributed African reptile species. With the present study, we contribute data for the leopard tortoise (Stigmochelys pardalis). It ranges from the Horn of Africa southward to South Africa and westwards to southern Angola. However, its natural occurrence is disputed for some southern regions. To clarify the situation, we used mtDNA sequences and 14 microsatellite loci from 204 individuals mainly from southern Africa. Our results retrieved five mitochondrial clades; one in the south and two in the north‐west and north‐east of southern Africa, respectively, plus two distributed further north. Using microsatellites, the southern clade matched with a well‐defined southern nuclear cluster, whilst the two northern clades from southern Africa corresponded to another nuclear cluster with three subclusters. One subcluster had a western and central distribution, another occurred mostly in the north‐east, and the third in a small eastern region (Maputaland), which forms part of a biodiversity hotspot. Genetic diversity was low in the south and high in the north of our study region, particularly in the north‐east. Our results refuted that translocations influenced the genetic structure of leopard tortoises substantially. We propose that Pleistocene climatic fluctuations caused leopard tortoises to retract to distinct refugia in southern and northern regions and ascribe the high genetic diversity in the north of southern Africa to genetic structuring caused by the survival in three refuges and subsequent admixture, whereas tortoises in the south seem to have survived in only one continuous coastal refuge.     

Taxonomy and biogeography of Bunopus spatalurus (Reptilia; Gekkonidae) from the Arabian Peninsula

In the last decade, taxonomic studies have drastically increased the number of species known to inhabit the Arabian deserts. While ongoing phylogenetic studies continue to identify new species and high levels of intraspecific genetic diversity, few studies have yet explored the biogeographic patterns in this arid region using an integrative approach. In the present work, we apply different phylogenetic methods to infer relationships within the Palearctic naked‐toed geckos. We specifically address for the first time the taxonomy and biogeography of Bunopus spatalurus Anderson, 1901, from Arabia using multilocus concatenated and species tree phylogenies, haplotype networks and morphology. We also use species distribution modelling and phylogeographic interpolation to explore the phylogeographic structure of Bunopus spatalurus hajarensis in the Hajar Mountains and the roles of climatic stability and possible biogeographic barriers on lineage occurrence and contact zones in this arid mountain endemism hot spot. According to the inferred topology recovered using concatenated and species tree methods, the genus ‘Bunopus’ is polyphyletic. Bunopus tuberculatus and B. blanfordii form a highly supported clade closely related to Crossobamon orientalis, while the two subspecies of ‘Bunopus’ spatalurus branch together as an independent highly supported clade that diverged during the Miocene according to our estimations. Within B. s. hajarensis, three geographically structured clades can be recognized that according to our estimations diverged during the Late Miocene to Pliocene. The paleodistribution models indicate climatic stability during the Late Pleistocene and the lineage occurrence, and predicted contact zones obtained from phylogeographic interpolation therefore probably result from the older splits of the groups when these lineages originated in allopatry. As demonstrated by the results of the multilocus molecular phylogenetic analyses and the topological test carried out in this study, the genus ‘Bunopus’ is not monophyletic. To resolve this, we resurrect the genus Trachydactylus Haas and Battersby, 1959; for the species formerly referred to as Bunopus spatalurus. Considering the morphological differences, the high level of genetic differentiation in the 12S mitochondrial gene and the results of the phylogenetic and the cmos haplotype network analysis, we elevate Trachydactylus spatalurus hajarensis to the species level Trachydactylus hajarensis (Arnold, 1980).     

Micro-spatial genetic structure in song sparrows (<Emphasis Type="Italic">Melospiza melodia</Emphasis>)

The spatial genetic structure of populations is strongly influenced by current and historical patterns of gene flow and drift, which in the simplest case, is limited by geographic distance. We examined the microspatial genetic structure within 33 populations of song sparrows (Melospiza melodia) which included eight subspecies located across coastal areas in southern British Columbia (BC) and California. We also examined the effect of water barriers and local density estimates on genetic structuring. Across both regions, positive genetic structure was detectable at distances of less than 10 km. Genetic divergence was highest in Californian subspecies, perhaps due to reduced gene flow across sub-specific contact zones. In BC, populations distributed across islands displayed greater genetic structuring over similar spatial scales than those across mainland sites, supporting the prediction that water barriers reduce gene flow in this species. Our results confirm both the expectation for fine-scale genetic structure in these generally sedentary subspecies, and the role of landscape features in generating geographic variation in genetic structure.     

Effects of historical forest contraction on the phylogeographic structure of Australo‐Papuan populations of the red‐legged pademelon (Macropodidae: Thylogale stigmatica)

Geographic patterns of genetic variation are strongly influenced by historical changes in species habitats. Whether such patterns are common to co‐distributed taxa may depend on the extent to which species vary in ecology and vagility. We investigated whether broad‐scale phylogeographic patterns common to a number of small‐bodied vertebrate and invertebrate species in eastern Australian forests were reflected in the population genetic structure of an Australo‐Papuan forest marsupial, the red‐legged pademelon (Macropodidae: Thylogale stigmatica). Strong genetic structuring of mtDNA haplotypes indicated the persistence of T. stigmatica populations across eastern Australia and southern New Guinea in Pleistocene refugial areas consistent with those inferred from studies of smaller, poorly dispersing species. However, there was limited divergence of haplotypes across two known historical barriers in the northeastern Wet Tropics (Black Mountain Barrier) and coastal mideastern Queensland (Burdekin Gap) regions. Lack of divergence across these barriers may reflect post‐glacial recolonization of forests from a large, central refugium in the Wet Tropics. Additionally, genetic structure is not consistent with the present delimitation of subspecies T. s. wilcoxi and T. s. stigmatica across the Burdekin Gap. Instead, the genetic division occurs further to the south in mideastern Queensland. Thus, while larger‐bodied marsupials such as T. stigmatica did persist in Pleistocene refugia common to a number of other forest‐restricted species, species‐specific local extinction and recolonization events have resulted in cryptic patterns of genetic variation. Our study demonstrates the importance of understanding individualistic responses to historical climate change in order to adequately conserve genetic diversity and the evolutionary potential of species.     

Diversification in wild populations of the model organism Anolis carolinensis: A genome‐wide phylogeographic investigation

The green anole (Anolis carolinensis) is a lizard widespread throughout the southeastern United States and is a model organism for the study of reproductive behavior, physiology, neural biology, and genomics. Previous phylogeographic studies of A. carolinensis using mitochondrial DNA and small numbers of nuclear loci identified conflicting and poorly supported relationships among geographically structured clades; these inconsistencies preclude confident use of A. carolinensis evolutionary history in association with morphological, physiological, or reproductive biology studies among sampling localities and necessitate increased effort to resolve evolutionary relationships among natural populations. Here, we used anchored hybrid enrichment of hundreds of genetic markers across the genome of A. carolinensis and identified five strongly supported phylogeographic groups. Using multiple analyses, we produced a fully resolved species tree, investigated relative support for each lineage across all gene trees, and identified mito‐nuclear discordance when comparing our results to previous studies. We found fixed differences in only one clade—southern Florida restricted to the Everglades region—while most polymorphisms were shared between lineages. The southern Florida group likely diverged from other populations during the Pliocene, with all other diversification during the Pleistocene. Multiple lines of support, including phylogenetic relationships, a latitudinal gradient in genetic diversity, and relatively more stable long‐term population sizes in southern phylogeographic groups, indicate that diversification in A. carolinensis occurred northward from southern Florida.     

Patterns of genetic differentiation in the <Emphasis Type="Italic">Gymnogeophagus gymnogenys</Emphasis> species complex,a neotropical cichlid from South American basins

The neotropical cichlid genus Gymnogeophagus is distributed in the Río de la Plata basin and in Dos Patos and Merín coastal lagoons on the border between Uruguay and southern Brazil. A phylogeographic approach based on mitochondrial cytochrome b analysis was performed to assess the patterns and processes of differentiation in this taxon. Gymnogeophagus gymnogenys showed high haplotype diversity (H = 0.992) and corrected mtDNA genetic distances ranged from 0 to 5.3%. Our analyses yielded robust support for the existence of four monophyletic groups within G. gymnogenys from the analyzed basins. No correlation between the aforementioned clades and geographic structure was found, since individuals belonging to different phylogenetic clades inhabit the same locality. The phylogeographic approach presented here showed that these four phylogroups (1, 2, 3 and 4) were sister groups. Our present findings would corroborate that G. gymnogenys could be integrated by different phylogenetic lineages, showing an explosive differentiation pattern and confirming the hypothesis that this taxon constitutes a species complex.     

Colonization history and genetic diversity: adaptive potential in early stage invasions

The introduction of Anolis cristatellus from the multiple species anole community of Puerto Rico in the Greater Antilles to the island of Dominica in the Lesser Antilles, with its solitary endemic anole, provides an example of a very recent, timed, single colonization. We investigate the geographic origin and adaptive potential of the Dominican population using a range of methods including mtDNA phylogeography, nuclear microsatellite variation and multiple paternity studies, as well as heritability estimates, common garden experiments and comparative geographic studies of quantitative scalation traits. Phylogeographic analysis of NADH2 and microsatellite studies suggests that the Dominican population arose from a set of individuals from the central west area of Puerto Rico within their endemic range. The multiple‐individual inoculation, together with sperm storage and evidence of multiple paternity indicate genetic variability and suggest the potential for adaptation by natural selection. Estimates of heritability, common garden experiments and broad sense Q_ST/F_ST ratios, linked to replicated comparisons along elevational transects go some way to suggesting that the invasive populations may be adapting by natural selection, in parallel with the endemic anole, in the brief period since their introduction.