Overseas Dispersal Research Articles

Early anthropoid primates: New data and new questions.

Although the evolutionary history of anthropoid primates (monkeys, apes, and humans) appears relatively well-documented, there is limited data available regarding their origins and early evolution. We review and discuss here the earliest records of anthropoid primates from Asia, Africa, and South America. New fossils provide strong support for the Asian origin of anthropoid primates. However, the earliest recorded anthropoids from Africa and South America are still subject to debate, and the early evolution and dispersal of platyrhines to South America remain unclear. Because of the rarity and incomplete nature of many stem anthropoid taxa, establishing the phylogenetic relationships among the earliest anthropoids remains challenging. Nonetheless, by examining evidence from anthropoids and other mammalian groups, we demonstrate that several dispersal events occurred between South Asia and Afro-Arabia during the middle Eocene to the early Oligocene. It is possible that a microplate situated in the middle of the Neotethys Ocean significantly reduced the distance of overseas dispersal.

Tempo‐spatial evolution of seed plant endemism in Taiwan island

AbstractAimIn Taiwan island, recent land‐bridge and oversea dispersal after the appearance of proto‐Taiwan (<6.5 Ma) is responsible for its biodiversity assembly. Radiations have also been widely reported in mountain systems. The tempo‐spatial route to the floral hotspot was determined through a meta‐analysis of the evolution of endemic plants.LocationTaiwan island and its adjacent regions.TaxonSeed plants.MethodsPublished dated phylogenies were compiled to infer the origin times represented by the stem ages. To determine the speciation mode, either in situ origin or dispersal origin, the ancestral range shift pattern and/or current distribution range of the sister taxa were used with 10 different biogeographical regions classified. Histograms quantifying the numbers of different origin modes within bins of 0.5 Ma were constructed. Probabilities of long‐distance dispersal (LDD) were evaluated.ResultsThe 125 sampled species originate between the late Eocene and late Pleistocene, of which 14 (11.2%) and 111 (88.8%) were derived before and after the emergence of proto‐Taiwan, respectively. Spatially, in situ speciation would have a bigger contribution to the formation of endemism than dispersal events (56.8% vs. 43.2%). The species with in situ origin (mean = 1.83 Ma) were significantly younger than those with dispersal origin (mean = 6.34 Ma). The main regions where dispersal occurred were South‐Central China (n = 29) and Southeast China (n = 28), followed by Japan (n = 14). High probabilities (60.8%) of LDD were found.Main ConclusionsSpatially, recent land‐bridge and oversea dispersal from the adjacent Asian flora is supported and the southern part of China was found to be the most important source. In situ speciation that may have correlated with mountain uplift, monsoon intensification and Pleistocene climatic fluctuations exerted greater contributions to the biodiversity there. Temporally, floral endemism predominantly occurred after the emergence of proto‐Taiwan. Additional investigations with more sophisticated sampling and genetic data are needed in the future.

Slow and steady wins the race: Diversification rate is independent from body size and lifestyle in Malagasy skinks (Squamata: Scincidae: Scincinae)

Most of the unique and diverse vertebrate fauna that inhabits Madagascar derives from in situ diversification from colonisers that reached this continental island through overseas dispersal. The endemic Malagasy Scincinae lizards are amongst the most species-rich squamate groups on the island. They colonised all bioclimatic zones and display many ecomorphological adaptations to a fossorial (burrowing) lifestyle. Here we propose a new phylogenetic hypothesis for their diversification based on the largest taxon sampling so far compiled for this group. We estimated divergence times and investigated several aspects of their diversification (diversification rate, body size and fossorial lifestyle evolution, and biogeography). We found that diversification rate was constant throughout most of the evolutionary history of the group, but decreased over the last 6–4 million years and independently from body size and fossorial lifestyle evolution. Fossoriality has evolved from fully quadrupedal ancestors at least five times independently, which demonstrates that even complex morphological syndromes – in this case involving traits such as limb regression, body elongation, modification of cephalic scalation, depigmentation, and eyes and ear-opening regression – can evolve repeatedly and independently given enough time and eco-evolutionary advantages. Initial diversification of the group likely occurred in forests, and the divergence of sand-swimmer genera around 20 Ma appears linked to a period of aridification. Our results show that the large phenotypic variability of Malagasy Scincinae has not influenced diversification rate and that their rich species diversity results from a constant accumulation of lineages through time. By compiling large geographic and trait-related datasets together with the computation of a new time tree for the group, our study contributes important insights on the diversification of Malagasy vertebrates.

Even short‐distance dispersal over a barrier can affect genetic differentiation in Gyraulus, an island freshwater snail

Abstract Dispersal is a fundamental mechanism for maintaining biodiversity, and long‐distance dispersal (LDD) has attracted the interest of many researchers owing to its unusual characteristics. Conventionally, LDD has been defined based on absolute and proportional distances; however, it has recently been redefined based on geographic and genetic limits. Based on this redefinition, short‐distance dispersal can have the same characteristics as LDD, depending upon the dispersal dynamics of an organism. However, the effects of LDD at a local scale on the genetic structure and diversification of organisms are poorly understood, since many studies have focused on definitive LDD, such as oversea dispersal. We focused on the freshwater snail Gyraulus sp. on an oceanic island, Chichijima Island, attempting to clarify the dynamics and effects of LDD on its genetic structure. We conducted molecular phylogenetic analyses, including divergence‐time estimation, using mitochondrial DNA and nuclear DNA markers to reveal the origin of the snail. In addition, we clarified the genetic structure, gene flow, and evolutionary history of snails on the island using mitochondrial DNA and genome‐wide single‐nucleotide polymorphisms. Finally, we followed a landscape ecology approach to identify barriers to dispersal. Our phylogenies suggested that the snail has a single origin. Based on our divergence–time estimation, colonisation was estimated to have occurred around the late Pliocene to early Pleistocene. Our population genetic analyses documented genetic differentiation even within this small oceanic island. Based on the divergence time estimation and approximate Bayesian computation using single‐nucleotide polymorphisms, the differentiation was estimated to have begun around the late Pleistocene. Little gene flow occurred between the geographically structured snail genetic groups. Landscape analysis suggested that catchment boundaries were a major barrier to dispersal. Considering the geography of the island, these results suggested that low‐frequency dispersal over barriers is an important factor in genetic differentiation within the island. Furthermore, dispersal over barrier may be considered LDD, even though the dispersal distance is only several kilometres. Genetic evidence also suggested that resistance to gene flow over the barrier, rather than distance, is more important in determining whether dispersal should be considered LDD. This suggests that a definition of LDD that depends only on the distance may mislead an understanding of dispersal mode.

Three dispersal routes out of Africa: A puzzling biogeographical history in freshwater planarians

AbstractAimFreshwater planarians may have a wide geographical range despite their assumed low vagility. Found across four continents, Dugesia may have either an ancient origin on a large palaeo landmass, followed by colonisation in different regions before continental fragmentation, or a more recent origin and subsequent transoceanic dispersal. We seek to resolve between these two hypotheses.LocationAfrica, Eurasia and Australasia.TaxonGenus Dugesia (Platyhelminthes: Tricladida: Dugesiidae).MethodsWe used data from the sequencing of six gene fragments and comprehensive taxonomic sampling of Dugesia from across its distribution range to reconstruct the phylogeny of this genus using maximum likelihood and bayesian inference methods. We conducted two phylogenetic dating analyses using Platyhelminthes fossils and palaeogeological events. Basing on the time‐calibrated molecular phylogenetic framework we evaluated the contribution of vicariance and dispersal to the biogeographical evolution of Dugesia. By reconstructing the ancestral areas and present‐day potential distribution using BioGeoBEARS and niche modelling, we elucidated the biogeographical history of the genus.ResultsThe present‐day distribution of Dugesia is a result of different vicariance and dispersal events. However, we also found evidence of transoceanic dispersal. Consistent with previous hypotheses, Dugesia dates to the Upper Jurassic in the Afro‐Malagasy Gondwana region. We unveiled a novel biogeographical scenario for the genus, involving multiple events of colonisation in Eurasia from continental Africa via at least three dispersal routes.Main conclusionsDugesia is an ancient genus having reached its present distribution through a complex history of dispersal and vicariant events following its origin in southern Gondwana. Despite the low vagility of Dugesia, we found evidence of their overseas dispersal.

Phylogeny, biogeography and classification of Teletisoptera (Blattaria: Isoptera)

AbstractTermites are social cockroaches distributed throughout warm temperate and tropical ecosystems. The ancestor of modern termites roamed the earth during the early Cretaceous, suggesting that both vicariance and overseas dispersal may have shaped the distribution of early diverging termites. We investigate the historical biogeography of three early diverging termite families –Stolotermitidae, Hodotermitidae and Archotermopsidae (clade Teletisoptera) – using the nuclear rRNA genes and mitochondrial genomes of 27 samples. Our analyses confirm the monophyly of Teletisoptera, with Stolotermitidae diverging from Hodotermitidae + Archotermopsidae approximately 100 Ma. Although Hodotermitidae are monophyletic, our results demonstrate the paraphyly of Archotermopsidae. Phylogenetic analyses indicate that the timing of divergence among the main lineages of Hodotermitidae + Archotermopsidae are compatible with vicariance. In the Stolotermitidae, however, the common ancestors of modern Porotermes Hagen and Stolotermes Hagen are roughly as old as 20 and 35 Ma, respectively, indicating that the presence of these genera in South America, Africa and Australia involved over‐water dispersals. Overall, our results suggest that early diverging termite lineages acquired their current distribution through a combination of over‐water dispersals and dispersal via land bridges. We clarify the classification by resolving the paraphyly of Archotermopsidae, restricting the family to Archotermopsis Desneux and Zootermopsis Emerson and elevating Hodotermopsinae (Hodotermopsis Holmgren) as Hodotermopsidae (status novum).

Patterns of diversification of the operculate land snail genus Cyclophorus (Caenogastropoda: Cyclophoridae) on the Ryukyu Islands, Japan

The Ryukyu Islands, an island chain in southwestern Japan, originated from land masses that separated from the Eurasian continent due to the formation of sea barriers about 1.55 million years ago. In this study, we investigated the phylogenetic relationships of the operculate land snail genus Cyclophorus (Caenogastropoda: Cyclophoridae) in the Ryukyu Archipelago and surrounding regions based on DNA sequence data. According to our results, all studied Cyclophorus specimens from Japan form a monophyletic group containing eight subclades. Six of these subclades were found only on the Ryukyu Islands. On most islands of the Ryukyu Archipelago, no more than one Cyclophorus subclade was recorded, which may be due to limited ecological niche space and competition. No subclade was found to occur on both sides of the Watase Line, a regional zoogeographical boundary. Divergence times were estimated based on a time-calibrated phylogeny. We found that multiple splits among the Japanese Cyclophorus subclades predate the emergence of major sea barriers in the Ryukyu Archipelago. Vicariance due to sea barrier formation, as assumed for many other taxa from the region, was thus likely not the main driver for subclade divergence in these snails. Instead, certain geographical features might have shaped the diversification of subclades prior to sea barrier formation. Given that Cyclophorus populations were also present on islands that have never been connected to other land masses, the snails must have colonized them via oversea dispersal. As not all nominal taxa corresponded to monophyletic groups, our molecular phylogenetic approach revealed that a taxonomic revision of the Japanese Cyclophorus fauna is necessary. The eight subclades may be regarded as potential species-level groups based on COI p-distances. A canonical discriminant analysis using shell morphological data revealed slight differences among the subclades.

Central American Snapping Turtle (Chelydridae, Chelydra rossignonii) on Utila Island, Honduras, Demonstrates Hurricanes are a Likely Past and Future Oversea Dispersal Pathway for Species Introduction in the Caribbean

The biogeographic origins of flora and fauna in the Caribbean have remained a hotly debated topic in island biogeography, with evidence to suggest that both vicariance (tectonic activity) and oversea dispersal mechanisms are at play in isolating species distributions and/or expanding them. Here we document the first evidence of the Central American Snapping Turtle (Chelydra rossignonii) on Utila Island, part of the Bay Islands, Honduras. Information is presented on two adult female individuals that were encountered washed ashore following separate extreme weather events in the region; most recently a single specimen was retrieved following Hurricane ETA in November 2020. Though dispersal in this case has not led to establishment, our novel observations may support previous inferences that long-distance overseas dispersal is a valid mechanism for explaining the occurrence of a potentially wide variety of terrestrial and freshwater biodiversity on the Bay Islands, as well as in the wider Caribbean.

Molecular phylogenetics of sub-Saharan African natricine snakes, and the biogeographic origins of the Seychelles endemic Lycognathophis seychellensis

Phylogenetic relationships of sub-Saharan African natricine snakes are understudied and poorly understood, which in turn has precluded analyses of the historical biogeography of the Seychelles endemic Lycognathophis seychellensis. We inferred the phylogenetic relationships of Seychelles and mainland sub-Saharan natricines by analysing a multilocus DNA sequence dataset for three mitochondrial (mt) and four nuclear (nu) genes. The mainland sub-Saharan natricines and L. seychellensis comprise a well-supported clade. Two maximally supported sets of relationships within this clade are (Limnophis,Natriciteres) and (Afronatrix,(Hydraethiops,Helophis)). The relationships of L. seychellensis with respect to these two lineages are not clearly resolved by analysing concatenated mt and nu data. Analysed separately, nu data best support a sister relationship of L. seychellensis with (Afronatrix,(Hydraethiops,Helophis)) and mt data best support a sister relationship with all mainland sub-Saharan natricines. Methods designed to cope with incomplete lineage sorting strongly favour the former hypothesis. Genetic variation among up to 33 L. seychellensis from five Seychelles islands is low. Fossil calibrated divergence time estimates support an overseas dispersal of the L. seychellensis lineage to the Seychelles from mainland Africa ca. 43–25 million years before present (Ma), rather than this taxon being a Gondwanan relic.

Genetic Variation of Scincella vandenburghi (Squamata; Scincidae) in Tsushima Island and Korea Revealed by Mitochondrial DNA

Abstract: Scincella vandenburghi is a small lygosomine skink, distributed in Tsushima Island and the Korean Peninsula as well as their adjacent islands. We analyzed the within-species genetic variation among the populations of Tsushima Island, Cheju Island, and the Korean Peninsula using partial sequences of mitochondrial DNA, cytochrome b and cytochrome c oxidase subunit I genes. We detected 20 haplotypes in total. Little genetic divergence was observed among the populations of S. vandenburghi from the Korean Peninsula, Tsushima Island, and Cheju Island. Genetic diversity was low in this species and demographic statistics suggested the recent expansion of distribution. Considering that Tsushima Island has been separated from the Korean Peninsula since 0.43 million years ago and that a narrow seaway had persisted between these two areas even during the Last Glacial Maximum, the low genetic divergence in S. vandenburghi suggests that this species expanded its range from the Korean Peninsula to Tsushima Island by oversea dispersal.

Phylogeny of Meloini blister beetles (Coleoptera, Meloidae) and patterns of island colonization in the Western Palaearctic

AbstractFlightless, phoretic insects of the tribe Meloini include several widespread species able to inhabit both mainland and oceanic and continental islands. Relationships between phoretic and non‐phoretic species of Meloini are unclear, precluding broad evolutionary and biogeographic analyses within the group. We provide a robust molecular phylogenetic framework for Meloini, with finer sampling in the Western Palaearctic, by analysing two nuclear (Wg, 18S) and two mtDNA (cox1, 16S) gene fragments of 24 species representing eight subgenera of Meloe and Physomeloe. Our phylogenetic analyses revealed that Meloe, as currently recognized, is paraphyletic. Our phylogenetic hypothesis clarifies several controversial relationships within the group. We provide a new taxonomic framework that better reflects the evolutionary relationships of the group by raising to genus all previously considered subgenera: Afromeloe Schmidt, 1913, Alveomeloe Pripisnova, 1987, Chiromeloe Reitter, 1911, Desertimeloe Kaszab, 1964, Eurymeloe Reitter, 1911, Lampromeloe Reitter, 1911, Lasiomeloe Reitter, 1911, Listromeloe Reitter, 1911, Meloegonius Reitter, 1911, Mesomeloe Reitter, 1911, Meloenellus Reitter, 1911, Micromeloe Reitter, 1911, Taphromeloe Reitter, 1911 and Treiodous Dugès, 1869; while Anchomeloe Iablokoff‐Khnzorian, 1983, is recovered as subgenus of Meloe. In addition, we conducted an extensive intraspecific sampling for four phoretic taxa (Meloe proscarabaeus, Meloe autumnalis, Eurymeloe mediterraneus and Eurymeloe tuccia) and used mtDNA phylogeographic analyses to unveil patterns of overseas dispersal. Our phylogeographic analyses revealed a high level of geographically unstructured haplotype diversity within taxa, suggesting that transmarine dispersal events have occurred multiple times along the evolutionary history of phoretic species of blister beetles. Larval phoresy may explain the existence of idiosyncratic biogeographic and phylogeographic patterns in these flightless organisms.

A Malagasy element in Continental Africa: a new subspecies of the rare Amauris nossima (Nymphalidae, Danainae) from the Kenyan coast

Amauris nossima Ward (Nymphalidae, Danainae) was known before this study only from Madagascar and the island of Mayotte, without clearly defined subspecies, but with five names considered invalid or infrasubspecific. It has generally been considered a rare species of butterfly classified by IUCN as vulnerable (Vu B1 + 2c). Here, it is reported for the first time from continental Africa. A new subspecies A. nossima mrima n. ssp. is described from two remnants of rain forest, Mrima and Buda, on the southern Kenyan coast, where it occurs sympatrically with Amauris ochlea Boisduval, widely distributed in East Africa. Their, previously predicted, sister-species status is confirmed by morphological (male and female genitalia) and partial mitochondrial (COI) data. The finding of A. nossima in Kenya opens the discussion on a possible recolonization of Africa from Madagascar, which would be an exception to a predominant biogeographical pattern of African origin of Malagasy butterflies via overseas dispersal.

Phylogeographic evidence that the distribution of cryptic euryhaline species in the Gambusia punctata species group in Cuba was shaped by the archipelago geological history

The main drivers of diversification of freshwater fishes in Cuba are not yet well understood. For example, salt tolerance was thought as the main factor involved in the diversification of Gambusia punctata species group in this archipelago. However, evidence from a recent DNA barcoding survey suggested the presence of cryptic species and no correlation between species delimitation and level of salinity. In this study, we analyzed the cryptic diversification of G. punctata species group in Cuba, based on a comprehensive sampling of its distribution and including habitats with different salinity levels. We evaluated the patterns of molecular divergence of the samples by sequencing a set of mitochondrial DNA (mtDNA) regions and genotyping nine nuclear microsatellite loci. We also used cytochrome b gene (cytb) partial sequences and these microsatellite loci to analyze population structure inside putative species. Five mtDNA well-differentiated haplogroups were found, four of them also identified by the analysis of the microsatellite polymorphism which corresponds to two already recognized species, G. punctata, and G. rhizophorae, and three putative new species. The extent of hybrid zones between these groups is also described. In each group, populations inhabiting environments with contrasting salinity levels were identified, indicating a generalized trait not specific to G. rhizophorae. The geographic distribution of the groups suggested a strong association with major relict territories of the Cuban Archipelago that was periodically joined or split-up by changes in seawater levels and land uplifts. Salinity tolerance might have facilitated sporadic and long-distance oversea dispersal but did not prevent speciation in the Cuban archipelago.

Multilocus phylogeny, species age and biogeography of the Lesser Antillean anoles

Lesser Antillean anoles provide classic examples of island radiations. A detailed knowledge of their phylogeny and biogeography, in particular how the age of species relate to the ages of their respective islands and the age of their radiation, is essential to elucidate the tempo and mechanisms of these radiations. We conduct a large-scale phylogenetic and phylogeographic investigation of the Lesser Antillean anoles using multiple genetic markers and comprehensive geographic sampling of most species. The multilocus phylogeny gives the first well-supported reconstruction of the interspecific relationships, and the densely sampled phylogeography reveals a highly dynamic system, driven by overseas dispersal, with several alternative post-dispersal colonisation trajectories. These radiations currently occupy both the outer-older (Eocene to Miocene), and the inner-younger (<8mybp), Lesser Antillean arcs. The origin of these radiations corresponds with the age of the ancient outer arc. However, the ages of extant species (compatible with the age of other small terrestrial amniotes) are much younger, about the age of the emergence of the younger arc, or less. The difference between the age of the radiation and the age of the extant species suggests substantial species turnover on older arc islands, most likely through competitive replacement. Although extant anoles are extremely speciose, this may represent only a fraction of their biodiversity over time. While paraphyly enables us to infer several recent colonization events, the absence of the younger arc islands and extant species at the earlier and middle stages of the radiation, does not allow the earlier inter-island colonization to be reliably inferred. Reproductive isolation in allopatry takes a very considerable time (in excess of 8my) and sympatry appears to occur only late in the radiation. The resolved multilocus phylogeny, and relative species age, raise difficulties for some earlier hypotheses regarding size evolution, and provide no evidence for within-island speciation.

Earliest known hominin activity in the Philippines by 709 thousand years ago.

Over 60 years ago, stone tools and remains of megafauna were discovered on the Southeast Asian islands of Flores, Sulawesi and Luzon, and a Middle Pleistocene colonization by Homo erectus was initially proposed to have occurred on these islands1-4. However, until the discovery of Homo floresiensis in 2003, claims of the presence of archaic hominins on Wallacean islands were hypothetical owing to the absence of in situ fossils and/or stone artefacts that were excavated from well-documented stratigraphic contexts, or because secure numerical dating methods of these sites were lacking. As a consequence, these claims were generally treated with scepticism 5 . Here we describe the results of recent excavations at Kalinga in the Cagayan Valley of northern Luzon in the Philippines that have yielded 57 stone tools associated with an almost-complete disarticulated skeleton of Rhinoceros philippinensis, which shows clear signs of butchery, together with other fossil fauna remains attributed to stegodon, Philippine brown deer, freshwater turtle and monitor lizard. All finds originate from a clay-rich bone bed that was dated to between 777 and 631 thousand years ago using electron-spin resonance methods that were applied to tooth enamel and fluvial quartz. This evidence pushes back the proven period of colonization 6 of the Philippines by hundreds of thousands of years, and furthermore suggests that early overseas dispersal in Island South East Asia by premodern hominins took place several times during the Early and Middle Pleistocene stages1-4. The Philippines therefore may have had a central role in southward movements into Wallacea, not only of Pleistocene megafauna 7 , but also of archaic hominins.

Morphological differentiation of the complex Pristurus sokotranus (Squamata: Sphaerodactylidae) from Socotra (Yemen)

Islands are excellent geographic scenarios to study speciation and diversification processes. Among non-volant tetrapods, reptiles are a model group to illustrate these processes due to their low over-sea dispersal. Although biodiversity catalogues are rather complete on islands, remote archipelagos still show high levels of undescribed diversity, including several remarkable examples of cryptic and unrecognized diversity. This should be investigated using integrative approaches, including both morphological and molecular data. The Socotra Archipelago (Yemen), is one of the most isolated continental archipelagos worldwide where a recent barcoding study has identified high levels of undescribed diversity within the reptile community. For example, the endemic semaphore gecko Pristurus sokotranus, the commonest reptile species of the archipelago, is recovered as paraphyletic (with the species P. samhaensis endemic to Samha and Dharsa branching inside it) and shows three geographically structured deep mitochondrial lineages within Socotra Island. To further analyse this, we examined 28 morphological characters (pholidotic, biometrics, and colouration) of P. sokotranus in order to uncover traits that differentiate the three mitochondrial clades. General Linear Models identified a set of traits that differed among clades and sexes. The rate of correct assignment to lineages using a discriminant analysis was 90.90% for males and 90.62% for females. The three clades showed differences in elevation and microhabitat preferences, as well as spatial structure on their distribution range on Socotra. These results corroborate the barcoding study and help to identify P. sokotranus individuals of each clade in the field. Our study further suggests the need of future integrative taxonomic studies including the species P. samhaensis and nuclear markers to revise the current taxonomy of P. sokotranus.

Integrative inference of population history in the Ibero-Maghrebian endemic Pleurodeles waltl (Salamandridae)

Inference of population histories from the molecular signatures of past demographic processes is challenging, but recent methodological advances in species distribution models and their integration in time-calibrated phylogeographic studies allow detailed reconstruction of complex biogeographic scenarios. We apply an integrative approach to infer the evolutionary history of the Iberian ribbed newt (Pleurodeles waltl), an Ibero-Maghrebian endemic with populations north and south of the Strait of Gibraltar. We analyzed an extensive multilocus dataset (mitochondrial and nuclear DNA sequences and ten polymorphic microsatellite loci) and found a deep east-west phylogeographic break in Iberian populations dating back to the Plio-Pleistocene. This break is inferred to result from vicariance associated with the formation of the Guadalquivir river basin. In contrast with previous studies, North African populations showed exclusive mtDNA haplotypes, and formed a monophyletic clade within the Eastern Iberian lineage in the mtDNA genealogy. On the other hand, microsatellites failed to recover Moroccan populations as a differentiated genetic cluster. This is interpreted to result from post-divergence gene flow based on the results of IMA2 and Migrate analyses. Thus, Moroccan populations would have originated after overseas dispersal from the Iberian Peninsula in the Pleistocene, with subsequent gene flow in more recent times, implying at least two trans-marine dispersal events. We modeled the distribution of the species and of each lineage, and projected these models back in time to infer climatically favourable areas during the mid-Holocene, the last glacial maximum (LGM) and the last interglacial (LIG), to reconstruct more recent population dynamics. We found minor differences in climatic favourability across lineages, suggesting intraspecific niche conservatism. Genetic diversity was significantly correlated with the intersection of environmental favourability in the LIG and LGM, indicating that populations of P. waltl are genetically more diverse in regions that have remained environmentally favourable through the last glacial cycle, particularly southern Iberia and northern Morocco. This study provides novel insights into the relative roles of geology and climate on the biogeography of a biodiversity hotspot.

Tropical ancient DNA reveals relationships of the extinct Bahamian giant tortoiseChelonoidis alburyorum

Ancient DNA of extinct species from the Pleistocene and Holocene has provided valuable evolutionary insights. However, these are largely restricted to mammals and high latitudes because DNA preservation in warm climates is typically poor. In the tropics and subtropics, non-avian reptiles constitute a significant part of the fauna and little is known about the genetics of the many extinct reptiles from tropical islands. We have reconstructed the near-complete mitochondrial genome of an extinct giant tortoise from the Bahamas (Chelonoidis alburyorum) using an approximately 1 000-year-old humerus from a water-filled sinkhole (blue hole) on Great Abaco Island. Phylogenetic and molecular clock analyses place this extinct species as closely related to Galápagos (C. niger complex) and Chaco tortoises (C. chilensis), and provide evidence for repeated overseas dispersal in this tortoise group. The ancestors of extant Chelonoidis species arrived in South America from Africa only after the opening of the Atlantic Ocean and dispersed from there to the Caribbean and the Galápagos Islands. Our results also suggest that the anoxic, thermally buffered environment of blue holes may enhance DNA preservation, and thus are opening a window for better understanding evolution and population history of extinct tropical species, which would likely still exist without human impact.

Fine‐scale demographic processes resulting from multiple overseas colonization events of the Japanese stream tree frog, Buergeria japonica

AbstractAimAmphibians are considered poor transoceanic dispersers because of their permeable skin. However, overseas dispersal of amphibian species has been revealed by recent phylogeographical studies and the role of overseas colonization of amphibians on their evolution and diversification has also been highlighted. However, no studies have investigated in detail the demographic processes related to these overseas colonization events. To clarify how amphibians achieve overseas colonization, we estimated the demographic history of the Japanese stream tree frog, Buergeria japonica, which is distributed on Amami Island and four northern neighbouring islands of the Tokara Archipelago, Japan.LocationSouth‐western islands of Japan and Taiwan.MethodsWe analysed the mitochondrial cytb gene and 20 microsatellite loci, and constructed phylogenetic trees based on these data. We also performed demographic analyses by applying approximate Bayesian computation (ABC) method and an isolation‐with‐migration model.ResultsPhylogenetic and demographic analyses based on cytb and 20 microsatellite genotype data revealed that divergence among island populations took place recently, mostly within the last few thousand years. Populations from the northern islands had reduced genetic diversity compared with southern islands, and ABC analyses supported the hypothesis that the species colonized islands from south to north.Main conclusionsGiven that the islands are separated from each other by deep sea, the recent divergences observed indicate overseas colonization events among the five islands. ABC analyses support the hypothesis that B. japonica underwent a stepping‐stone overseas colonization from southern to northern neighbouring islands during the past few thousand years accompanied by multiple founder effects. These results support the hypothesis that overseas colonization could have had a substantial impact on amphibian evolution and diversification.

Not only in the temperate zone: independent gametophytes of two vittarioid ferns (Pteridaceae, Polypodiales) in East Asian subtropics.

Independent gametophyte ferns are unique among vascular plants because they are sporophyteless and reproduce asexually to maintain their populations in the gametophyte generation. Such ferns had been primarily discovered in temperate zone, and usually hypothesized with (sub)tropical origins and subsequent extinction of sporophyte due to climate change during glaciations. Presumably, independent fern gametophytes are unlikely to be distributed in tropics and subtropics because of relatively stable climates which are less affected by glaciations. Nonetheless, the current study presents cases of two independent gametophyte fern species in subtropic East Asia. In this study, we applied plastid DNA sequences (trnL-L-F and matK + ndhF + chlL datasets) and comprehensive sampling (~80%) of congeneric species for molecular identification and divergence time estimation of these independent fern gametophytes. The two independent gametophyte ferns were found belonging to genus Haplopteris (vittarioids, Pteridaceae) and no genetic identical sporophyte species in East Asia. For one species, divergence times between its populations imply recent oversea dispersal(s) by spores occurred during Pleistocene. By examining their ex situ and in situ fertility, prezygotic sterility was found in these two Haplopteris, in which gametangia were not or very seldom observed, and this prezygotic sterility might attribute to their lacks of functional sporophytes. Our field observation and survey on their habitats suggest microhabitat conditions might attribute to this prezygotic sterility. These findings point to consideration of whether recent climate change during the Pleistocene glaciation resulted in ecophysiological maladaptation of non-temperate independent gametophyte ferns. In addition, we provided a new definition to classify fern gametophyte independences at the population level. We expect that continued investigations into tropical and subtropical fern gametophyte floras will further illustrate the biogeographic significance of non-temperate fern gametophyte independence.