Major Biogeographic Barrier Research Articles

Different roles of the Amazon-Orinoco barrier on the genetic structure of two sardine genera from the Western Atlantic Ocean

Three sardine species of Harengula and one of Opisthonema (Clupeiformes, Clupeidae) are known in the Western Atlantic, where the Amazon-Orinoco plume has been recognized as a major biogeographic barrier, albeit permeable to larger and generalist species. Here we used mitochondrial cox1 gene DNA sequences to check the lineage delimitation of both genera, testing the influence of the Amazon-Orinoco barrier (AOB) and marine provinces on their phylogeographic structure. Results indicate that the two genera are differently affected by the AOB, including cryptic speciation in Harengula and population structure in Opisthonema. Harengula show a broad distribution in the Brazilian Province (BRA) distinct from H. clupeola and H. jaguana from the Greater Caribbean Region (GCR). Divergence time between Harengula from the GCR vs. BRA was estimated as about 2.4 Mya, which coincides with the period of increasing sediment and freshwater discharge of the Amazon River in the Atlantic. Results also indicate the existence of a single species of Opisthonema, albeit with population structuring related to the marine provinces. Since species of both genera are relevant to artisanal fisheries and the maintenance of oceanic ecosystems, these results may help in fisheries management of these important marine resources.

Systematic revision of the eastern Queensland land snail genus Figuladra Köhler and Bouchet, 2020 based on mitochondrial phylogenetics and comparative morpho-anatomy (Eupulmonata, Camaenidae)

ABSTRACT The current study revises the systematic taxonomy of Figuladra, a genus of camaenid land snails endemic to eastern Queensland, based on the investigation of many recently collected ethanol-preserved samples as well as historic museum material, including types. We employed comparative analyses to investigate the variation in morphological features (shell, penial anatomy) and performed phylogenetic analyses of mitochondrial 16S rDNA sequences to test species hypotheses. Phylogenetic analyses recovered three principal mitochondrial clades, one occurring in mid-east Queensland, one in south-east Queensland, and another in the upland areas of south-east Queensland. We recognise altogether 15 accepted species, including four that are newly described herein (i.e., Figuladra finlaysoni sp. nov., F. robertirwini sp. nov., F. bromileyorum sp. nov. and F. vidulus sp. nov.). The status of 11 previously described species has been assessed and revised diagnoses are provided for each of these. Species of the south-east Queensland clade revealed comparatively low levels of genetic and morphological differentiation and may represent examples of more recent, conceivably ongoing, speciation. Figuladra species have allopatric distributions with their ranges being separated by altitudinal or riverine barriers. Particularly the St Lawrence Gap dry corridor has been identified as a major biogeographic barrier separating two principal clades of Figuladra.

The natural and human-mediated expansion of a human-commensal lizard into the fringes of Southeast Asia

BackgroundHuman-commensal species often display deep ancestral genetic structure within their native range and founder-effects and/or evidence of multiple introductions and admixture in newly established areas. We investigated the phylogeography of Eutropis multifasciata, an abundant human-commensal scincid lizard that occurs across Southeast Asia, to determine the extent of its native range and to assess the sources and signatures of human introduction outside of the native range. We sequenced over 350 samples of E. multifasciata for the mitochondrial ND2 gene and reanalyzed a previous RADseq population genetic dataset in a phylogenetic framework.ResultsNuclear and mitochondrial trees are concordant and show that E. multifasciata has retained high levels of genetic structure across Southeast Asia despite being frequently moved by humans. Lineage boundaries in the native range roughly correspond to several major biogeographic barriers, including Wallace’s Line and the Isthmus of Kra. Islands at the outer fringe of the range show evidence of founder-effects and multiple introductions.ConclusionsMost of enormous range of E. multifasciata across Southeast Asia is native and it only displays signs of human-introduction or recent expansion along the eastern and northern fringe of its range. There were at least three events of human-introductions to Taiwan and offshore islands, and several oceanic islands in eastern Indonesia show a similar pattern. In Myanmar and Hainan, there is a founder-effect consistent with post-warming expansion after the last glacial maxima or human introduction.

Molecular diversity of Pseudoscorpiones in southern High Appalachian leaf litter.

The Pseudoscorpiones fauna of North America is diverse, but in regions like the southern Appalachian Mountains, they are still poorly documented with respect to their species diversity, distributions and ecology. Several families have been reported from these mountains and neighbouring areas. Here we analyse barcoding data of 136 specimens collected in leaf litter, most of them from high-elevation coniferous forest. We used ASAP as a species delimitation method to obtain an estimation of the number of species present in the region. For this and based on interspecific genetic distance values previously reported in Pseudoscorpions, we considered three different genetic Kimura two-parameter distance thresholds (3%/5%/8%), to produce more or less conservative estimates. These distance thresholds resulted in 64/47/27 distinct potential species representing the families Chthoniidae (33/22/12 species) and Neobisiidae (31/25/15) and at least six different genera within them. The diversity pattern seems to be affected by the Asheville Depression, a major biogeographic barrier in this area, with a higher diversity to the west of this geographic feature, particularly within the family Neobisiidae. The absence of representatives from other families amongst our studied samples may be explained by differences in their ecological requirements and occupation of different microhabitats.

A Taxonomic Hide and Seek: Phylogenetic and Phylogeographic Relationships in the Southeast Asian Box Turtle, <i>Cuora amboinensis</i> (Riche in Daudin, 1801)

Cuora amboinensis is considered to be the most wide-ranging member of its genus and has one of the widest distributions of all geoemydid turtle species. The range of Cuora amboinensis spans major biogeographic barriers and encompasses diverse habitats. The genetics (nuDNA and mtDNA) and morphometry of 288 Cuora amboinensis sensu lato (s.l.) specimens from across its range were analyzed, and we identified five divergent species-level clades and two subspecies-level clades. One of the two identified potential subspecies lacked reliable locality data, requiring further field research before taxonomic steps can be undertaken. We designate a neotype for Cuora amboinensis sensu stricto and elevate both Cuora amboinensis couro and Cuora amboinensis lineata to species-level taxa. In addition, we describe two new species and one new subspecies from the «Cuora amboinensis» complex. The wide distribution of Cuora amboinensis s.l. is problematic because it is indigenous to many Pacific and Indian Ocean islands. We sought to clarify plausible dispersal hypotheses across islands using phylogeographic analyses.

Multilocus phylogeography, population genetics and niche evolution of Australian brown and black-tailed treecreepers (Aves:Climacteris)

AbstractThe Carpentarian barrier across north-eastern Australia is a major biogeographic barrier and a generator of biodiversity within the Australian Monsoonal Tropics. Here we present a continent-wide analysis of mitochondrial (control region) and autosomal (14 anonymous loci) sequence and indel variation and niche modelling of brown and black-tailed treecreepers (Climacteris picumnus and Climacteris melanurus), a clade with a classic distribution on either side of the Carpentarian barrier. mtDNA control region sequences exhibited reciprocal monophyly and strong differentiation (Fst = 0.91), and revealed a signature of a recent selective sweep in C. picumnus. A variety of tests support an isolation-with-migration model of divergence, albeit with low levels of gene flow across the Carpentarian barrier and a divergence time between species of ~1.7–2.8 Mya. Palaeoecological niche models show that both range size as measured by available habitat and estimated historical population sizes of both species declined in the past ~600 kyr and that the area of interspecific range overlap was never historically large, perhaps decreasing opportunities for extensive gene flow. The relatively long divergence time and low opportunity for gene flow may have facilitated speciation more so than in other co-distributed bird taxa across the Australian Monsoonal Tropics.

Biotic regionalization of freshwater fishes in Northern Middle America highlights high beta diversity created by prominent biogeographic barriers

Northern Middle America (NoMA) is considered a transition zone between the Nearctic and Neotropical biogeographic realms. In this region, Nearctic and Neotropical freshwater fishes create regional faunas of mixed origin, but their general biogeographic patterns have not been quantified. To identify such patterns, we delineate biogeographic regions (BRs) and major biogeographic barriers of NoMA and summarize patterns of faunal similarity among BRs. We used clustering analysis on a presence-absence matrix of primary and secondary freshwater fishes to group 97 level-6 HydroBASINs units spanning NoMA into BRs. We assessed statistical support of clusters using one-way analysis of similarity and implemented a species-indicator analysis. We delineated biogeographic barriers with the software Barrier 2.2 and determined faunal similarity among BRs using beta diversity-Jaccard dissimilarity and producing a minimum-spanning tree. Seven statistically distinctive and geographically coherent BRs were delineated and described. Barrier analysis identified three major barriers within NoMA. The first barrier combines the Sea of Cortés (Gulf of California) and Sierra de Juárez-Cerro Gordo highlands. The second combines the Trans-Mexican Volcanic Belt, Sierra Madre del Sur, and Sierra Madre de Chiapas highlands. The third combines the Río Grande Rift, Sierra Madre Occidental, and Mesa Central highlands. Faunal dissimilarity was very high among BRs, with lowest dissimilarity (92%) between the Balsas-Nacaome and Grijalva-Usumacinta BRs. Boundaries of NoMA BRs do not correspond with political boundaries. We concluded that bioregions of NoMA are faunally distinct, with limited overlap due to presence of strong, long-standing geographical barriers enhanced by aridity in the North.

Giant clam (Tridacna) distribution in the Gulf of Oman in relation to past and future climate

The Oman upwelling zone (OUZ) creates an unfavorable environment and a major biogeographic barrier for many coral reef species, such as giant clams, thus promoting and maintaining faunal differences among reefs on the east and west side of the Arabian Peninsula. We record the former existence of Tridacna in the Gulf of Oman and review its stratigraphic distribution in the Persian Gulf to provide new insights on the connectivity of coral reef habitats around southern Arabia under changing climate and ocean conditions. Fossil shells were carbon-14 dated and employed as sclerochronological proxy archives. This reveals that the Omani population represents a last glacial colonization event during the Marine Isotope Stage 3 interstadial under colder-than-present temperatures and variable upwelling intensity linked to Dansgaard-Oeschger climate oscillations. It was favored by temperatures just above the lower threshold for the habitat-forming reef coral communities and instability of the upwelling barrier. We conclude that the distribution of Tridacna in the northern Arabian Sea is generally limited by either strong upwelling or cool sea surface temperature under gradually changing climate conditions at the interglacial-glacial scale. Opportunities for dispersal and temporary colonization existed only when there was a simultaneous attenuation of both limiting factors due to high-frequency climate variability. The OUZ will unlikely become a future climate change refuge for giant clams because they will be exposed either to thermal stress by rapid anthropogenic Indian Ocean warming or to unfavorable upwelling conditions.

Cenozoic weathering of fluvial terraces and emergence of biogeographic boundaries in Central Amazonia

The study of paleofluvial dynamics is crucial to understand the role of rivers as biogeographic boundaries in Amazonia during the Cenozoic. In central Amazonia, Mesozoic and Cenozoic fluvial deposits - Alter do Chão, Iranduba and Novo Remanso Formations - host supergene iron oxides and record changes in the distribution of flooded and non-flooded (upland) environments. Geochronological data on these deposits are still scarce to constrain past landscape changes. Therefore, in this study we investigate iron oxides precipitated within weathering profiles developed on ancient fluvial terraces to access the interplay between flooded and non-flooded environments in central Amazonia. We aimed to trace the history of abandonment of alluvial plains and the subsequent weathering of lowland sediment deposits during the Cenozoic. We identified at least two main periods of iron oxide precipitation: (1) one starting before ~42 Ma and ending at ~18 Ma; and (2) a well-defined humid and weathering prone phase between ~8 and 1 Ma. Dominant goethite precipitation marks a major climatic shift towards more humid conditions from ~3 Ma. The increase in water discharge of the Negro and Solimões rivers possibly promoted fluvial incision and conversion of floodplains into long-lasting upland terrains as indicated by the development of lateritic weathering profiles. This major phase of upland expansion corroborates upland birds phylogenetic data, which indicate the emergence of a major biogeographic barrier in central Amazonia during late Pliocene/Pleistocene. • Refining the age of the fluvial sedimentary units in central Amazonia • Multiple Cenozoic discrete weathering phases in central Amazonia • Linking weathering phases with fluvial landscape changes • Constraining the emergence of a major biogeographic boundary

Cryptic diversity of Rhinolophus lepidus in South Asia and differentiation across a biogeographic barrier

Peninsular India is an important region for mammalian diversification and harbors major biogeographic barriers. However, little is known about the role of this region in the diversification of bats though it harbors high chiropteran diversity. In this study, we used phenotypic, acoustic, and genetic markers to assess the diversification of Rhinolophus lepidus bats in South Asia. We first investigated if peninsular India is associated with speciation of R. lepidus. Further, we tested if the Palghat Gap acts as a biogeographic barrier to gene flow in this species. Our results revealed cryptic genetic diversity in peninsular India suggesting that this region holds at least one endemic species level lineage of the R. lepidus species complex.  Analyses of populations of R. lepidus across the Palghat Gap in the Western Ghats revealed clinal variation in phenotype, with bats south of this barrier being bigger and emitting echolocation calls of higher frequency. We also observed that populations on either side of the Palghat Gap have remained genetically isolated since the mid-Holocene.

Major biogeographic barriers in eastern Australia have shaped the population structure of widely distributed Eucalyptus moluccana and its putative subspecies.

We have investigated the impact of recognized biogeographic barriers on genetic differentiation of grey box (Eucalyptus moluccana), a common and widespread tree species of the family Myrtaceae in eastern Australian woodlands, and its previously proposed four subspecies moluccana, pedicellata, queenslandica, and crassifolia. A range of phylogeographic analyses were conducted to examine the population genetic differentiation and subspecies genetic structure in E. moluccana in relation to biogeographic barriers. Slow evolving markers uncovering long term processes (chloroplast DNA) were used to generate a haplotype network and infer phylogeographic barriers. Additionally, fast evolving, hypervariable markers (microsatellites) were used to estimate demographic processes and genetic structure among five geographic regions (29 populations) across the entire distribution of E. moluccana. Morphological features of seedlings, such as leaf and stem traits, were assessed to evaluate population clusters and test differentiation of the putative subspecies. Haplotype network analysis revealed twenty chloroplast haplotypes with a main haplotype in a central position shared by individuals belonging to the regions containing the four putative subspecies. Microsatellite analysis detected the genetic structure between Queensland (QLD) and New South Wales (NSW) populations, consistent with the McPherson Range barrier, an east‐west spur of the Great Dividing Range. The substructure was detected within QLD and NSW in line with other barriers in eastern Australia. The morphological analyses supported differentiation between QLD and NSW populations, with no difference within QLD, yet some differentiation within NSW populations. Our molecular and morphological analyses provide evidence that several geographic barriers in eastern Australia, including the Burdekin Gap and the McPherson Range have contributed to the genetic structure of E. moluccana. Genetic differentiation among E. moluccana populations supports the recognition of some but not all the four previously proposed subspecies, with crassifolia being the most differentiated.

A new species of Bolitoglossa (Caudata: Plethodontidae) of the Bolitoglossa franklini group from an isolated cloud forest in northern Guatemala.

We describe Bolitoglossa qeqom sp. nov. from an isolated cloud forest in Cerro Guachmalén, Alta Verapaz, Guatemala, based on multiple lines of evidence (morphological, molecular, and biogeographic data). This region comprises a mountain ridge without previous herpetological surveys. The new species is a large salamander with uniform purplish-black coloration and is distinguished by having relatively long legs with only one costal groove between adpressed limbs, numerous maxillary teeth, few vomerine teeth, only one phalange free of webbing in digit III of feet, and a relatively short tail. It is geographically closest to its sister clade of B. lincolni + B. franklini and the xeric Chixoy river canyon appears to be the major biogeographic barrier that isolated the new taxon. The cloud forest inhabited by this species has undergone severe habitat destruction in the region and land conservation actions are urgent.

Gene flow across a major biogeographic barrier is not increasing under climate change for the barnacle Catomerus polymerus

On the south-east coast of Australia, the impermeability of the Southeast Australian Biogeographic Barrier (SEABB) limits the dispersal of many intertidal taxa, but current flow across the SEABB is expected to be increasing under climate change. The surf barnacle Catomerus polymerus has extensive populations on either side of the barrier that both mitochondrial cytochrome c oxidase subunit I (mtCOI) sequence data and surveys using 4-6 microsatellite loci imply have been separated for millennia (>167000 yr). Nevertheless, these data sets (based on collections from 2005-2012) also imply that there has been some recent dispersal across the SEABB. If trans-barrier migration is now possible, then in the absence of selection the differentiation of lineages should be eroded. Next-generation sequencing provides the opportunity to both better quantify levels of population differentiation attributable to the SEABB and to determine if there is regional selection. Our data (3801 single nucleotide polymorphisms) for individuals collected in 2019 within 3 eastern and 4 western sites support earlier reports of low population differentiation within eastern and western regions (FST < 0.021) and the strong regional separation of eastern and western lineages (FRT = 0.23). Moreover, in contrast to earlier studies, we did not detect any putative migrants, with all individuals assigning most strongly to their sampling region. Most strikingly, analysis using BAYESCAN implied that 47 loci (1.24%) of our surveyed loci show evidence of significant regional diversifying selection, which implies that even if C. polymerus larvae are able to cross the barrier, they will be strongly disfavoured by selection.

Systematics, biogeography and evolution of the Saharo-Arabian naked-toed geckos genus Tropiocolotes

Plate tectonics constitute one of the main mechanisms of biological diversification on Earth, often being associated with cladogenetic events at different phylogenetic levels, as well as with exchange of faunas and floras across previously isolated biogeographic regions. North Africa and Arabia share a complex geological history that dates back to the break-up of the Arabian plate from the African plate ~30–25 Mya, followed by various geological events, such as the formation of the Red Sea or the connection between the African, Arabian and Eurasian plates. Species with Saharo-Arabian distributions have shown a close association between their evolutionary history and these geological events. In this study, we investigate the systematics, biogeography and evolution of the genus Tropiocolotes, a group of small ground-dwelling geckos, comprised by 12 species distributed from the Atlantic coast of North Africa to southwestern Iran. Species delimitation analyses uncovered the existence of high levels of undescribed diversity, with forms here considered at the species level including Tropiocolotes tripolitanus (Mauritania and southern Morocco), T. nattereri (southern Israel) and T. scorteccii (Yemen and Oman). Phylogenetic and biogeographic analyses recovered two main clades, an exclusively African clade and a Saharo–Arabian clade, that split ~25 Mya following the vicariant event mediated by the separation of the Arabian and African plates. The complex geological activity around the Red Sea is associated with the diversification within the Saharo-Arabian clade, including the colonization of North Africa from a second Tropiocolotes group. Results also provide new insights into the geographic distribution of Tropiocolotes nubicus, previously considered as exclusively associated to the Nile River valley, extending its known distribution further west, up to the Central Mountains of the Sahara. Accordingly, the Nile River seems to act as a major biogeographic barrier, separating Tropiocolotes nubicus and T. steudneri in their western and eastern margins, respectively.

Moving beyond the riverine barrier vicariant paradigm.

One of the main goals of evolutionary biology is to understand the processes behind current patterns of biodiversity. Shared geographic distributions among unrelated species may result from a common history, providing a unique opportunity to assess the evolution of the landscape and the origins of biodiversity. Until recently, vicariance prevailed as the main evolutionary model to be tested, and the riverine barrier hypothesis the null model for taxa with river-bounded distributions. In recent years, however, multispecies comparative approaches have unveiled idiosyncratic scenarios among codistributed species, suggesting that rivers may or may not play a role in the speciation process. In a From the Cover article in this issue of Molecular Ecology, Kopuchian et al. (2020) explore predictions of the riverine barrier hypothesis in a major subtropical river system, evaluating the degree of mitochondrial and nuclear genomic differentiation in seven bird species with allegedly morphological differentiation across the Paraná-Paraguay river system. The authors show that in only one case, the genetic differentiation was concordant with the river. Interestingly, pairs presented disparate divergence times and/or distinct demographic histories. In most cases, putative contact zones broadly coincided with the transition of different ecoregions, such as the Espinal/Chaco ecological ecotone. These findings argue against the role of the Paraná-Paraguay river system as a major biogeographic barrier and highlight the need to explore the role of ecology in species diversification. Here, we feature different perspectives for studying the processes governing species divergence and suggest a basic protocol to advance the study of riverine barriers.

Sea water shaping the freshwater biota: Hidden diversity and biogeographic history in the Paracanthocobitis zonalternans species complex (Teleostei: Nemacheilidae) in western Southeast Asia

Western Southeast Asia is hosting one of the world’s most diverse faunas, and one of the reasons for this huge diversity is the complex geologic past of the area, increasing the frequency of isolation and expansion events over evolutionary time scale. As an example case, the present study reveals the phylogeny and biogeographic history of the Paracanthocobitis zonalternans species complex, small benthic freshwater fish (Teleostei: Nemacheilidae) that are commonly occurring across western Southeast Asia (from central Myanmar through western and southern Thailand to northern Malaysia). The group is particularly interesting since it occurs in three biogeographic subdivisions (Indian, Indochinese, Malay/Sundaic) and across all of the major biogeographic barriers in the region. Basing on mitochondrial and nuclear sequence data of 93 samples from about 50 localities we found six major clades, most with exclusive geographic distribution. Divergence time dated the origin of the P. zonalternans species complex to early Miocene (17.8 MYA) and a biogeographic analysis identified the Tenasserim region as the ancestral region. From this region the fish spread during periods of lowered global sea level, particularly during late Miocene (11-8 MYA) northwards into all Burmese river basins and southwards into south Thailand and northern Malaysia. Besides lowered global sea level periods, local stream capture events allowed the complex to expand, e.g. into the Mae Klong basin. Strong fragmentations during periods with elevated sea level during the Pliocene and Pleistocene repeatedly restricted populations to refuges and shaped the observed major lineages. Our results document a higher diversity within the P. zonalternans species complex than formerly believed and a strong impact of global sea level on its evolutionary history. Low sea levels promoted dispersal and elevated sea levels fragmentation events. A very similar impact of sea level changes can be expected in all stationary fauna (freshwater and terrestrial) in all non-mountainous coastal regions worldwide.

Genome‐wide markers untangle the green‐lizard radiation in the Aegean Sea and support a rare biogeographical pattern

AbstractAimThe Aegean Sea constitutes a major biogeographic barrier between the European and Asian continents and several models of diversification in the Aegean have been documented. Here, we test three of those models for the Aegean green‐lizards (Lacerta trilineata–pamphylica group): Vicariance versus Overland Dispersal versus Island Stepping‐stone Dispersal. We investigate these hypotheses and complement our knowledge on the impact of the Aegean Barrier on east Mediterranean taxa.LocationAegean Sea, east Mediterranean.TaxonLacerta lizards.MethodsWe analysed ddRAD loci (double‐digest restriction‐site‐associated DNA) to estimate species‐trees under coalescent models and maximum likelihood trees using concatenation. We performed hierarchical population structure analyses and inferred ancestral distribution‐areas. We also sequenced the complete cytochrome b gene and produced a time‐calibrated mtDNA gene‐tree to conduct a critical comparison with previous studies.ResultsAegean green‐lizards diverged into four main groups in parallel during the Late Pliocene with distributions to the East and West of the Aegean. The Eastern group includes Lacerta pamphylica and East Aegean L. trilineata, while the Western group contains the Central Cyclades populations and the remaining populations of the Balkan Peninsula. The Aegean green‐lizards’ ancestor occurred in Anatolia, while the West lineage ancestor occurred in the Central Cyclades islands, revealing a dispersal between the two regions. The radiations of all major green‐lizard groups, including trilineata+pamphylica, occurred in parallel in the Late Pliocene.Main ConclusionsIn contrast to previously suggested biogeographical hypotheses for the group, based on mtDNA, the Island Stepping‐stone Dispersal scenario is strongly supported. Green lizards offer a rare paradigm of diversification in the Aegean, where populations largely expanded their geographical distribution and crossed the Aegean Barrier using the central Aegean islands as stepping stones.

Contrasting population genetic structure in three aggregating groupers (Percoidei: Epinephelidae) in the Indo-West Pacific: the importance of reproductive mode

BackgroundUnderstanding the factors shaping population genetic structure is important for evolutionary considerations as well as for management and conservation. While studies have revealed the importance of palaeogeographic changes in shaping phylogeographic patterns in multiple marine fauna, the role of reproductive behaviour is rarely considered in reef fishes. We investigated the population genetics of three commercially important aggregating grouper species in the Indo-West Pacific, namely the camouflage grouper Epinephelus polyphekadion, the squaretail coral grouper Plectropomus areolatus, and the common coral trout P. leopardus, with similar life histories but distinct spatio-temporal characteristics in their patterns of forming spawning aggregations.ResultsBy examining their mitochondrial control region and 9–11 microsatellite markers, we found an overarching influence of palaeogeographic events in the population structure of all species, with genetic breaks largely coinciding with major biogeographic barriers. The divergence time of major lineages in these species coincide with the Pleistocene glaciations. Higher connectivity is evident in E. polyphekadion and P. areolatus that assemble in larger numbers at fewer spawning aggregations and in distinctive offshore locations than in P. leopardus which has multiple small, shelf platform aggregations.ConclusionsWhile palaeogeographic events played an important role in shaping the population structure of the target species, the disparity in population connectivity detected may be partly attributable to differences in their reproductive behaviour, highlighting the need for more investigations on this characteristic and the need to consider reproductive mode in studies of connectivity and population genetics.

Do ecological communities disperse across biogeographic barriers as a unit?

Biogeographic barriers have long been implicated as drivers of biological diversification, but how these barriers influence co-occurring taxa can vary depending on factors intrinsic to the organism and in their relationships with other species. Due to the interdependence among taxa, ecological communities present a compelling opportunity to explore how interactions among species may lead to a shared response to historical events. Here we collect single nucleotide polymorphism data from five commensal arthropods associated with the Sarracenia alata carnivorous pitcher plant, and test for codiversification across the Mississippi River, a major biogeographic barrier in the southeastern United States. Population genetic structure in three of the ecologically dependent arthropods mirrors that of the host pitcher plant, with divergence time estimates suggesting two of the species (the pitcher plant moth Exyra semicrocea and a flesh fly Sarcophaga sarraceniae) dispersed synchronously across this barrier along with the pitcher plant. Patterns in population size and genetic diversity suggest the plant and ecologically dependent arthropods dispersed from east to west across the Mississippi River. In contrast, species less dependent on the plant ecologically show discordant phylogeographic patterns. This study demonstrates that ecological relationships may be an important predictor of codiversification, and supports recent suggestions that organismal trait data should be prominently featured in comparative phylogeographic investigations.

A genomic assessment of species boundaries and hybridization in a group of highly polymorphic anoles (distichus species complex).

Delimiting young species is one of the great challenges of systematic biology, particularly when the species in question exhibit little morphological divergence. Anolis distichus, a trunk anole with more than a dozen subspecies that are defined primarily by dewlap color, may actually represent several independent evolutionary lineages. To test this, we utilized amplified fragment length polymorphisms (AFLP) genome scans and genetic clustering analyses in conjunction with a coalescent‐based species delimitation method. We examined a geographically widespread set of samples and two heavily sampled hybrid zones. We find that genetic divergence is associated with a major biogeographic barrier, the Hispaniolan paleo‐island boundary, but not with dewlap color. Additionally, we find support for hypotheses regarding colonization of two Hispaniolan satellite islands and the Bahamas from mainland Hispaniola. Our results show that A. distichus is composed of seven distinct evolutionary lineages still experiencing a limited degree of gene flow. We suggest that A. distichus merits taxonomic revision, but that dewlap color cannot be relied upon as the primary diagnostic character.