Multiple Colonization Events Research Articles

Evidence of multiple colonizations as a driver of black fly diversification in an oceanic island.

True oceanic islands typically host reduced species diversity together with high levels of endemism, which make these environmental set-ups ideal for the exploration of species diversification drivers. In the present study, we used black fly species (Diptera: Simuliidae) from Reunion Island as a model to highlight the main drivers of insect species diversification in this young and remote volcanic island located in the Southwestern Indian Ocean. Using local and regional (Comoros and Seychelles archipelagos) samples as well as specimens from continental Africa, we tested the likelihood of two distinct scenarios, i.e. multiple colonizations vs. in-situ diversification. For this, posterior odds were used to test whether species from Reunion did form a monophyletic group and we estimated divergence times between species. Three out of the four previously described Reunion black fly species could be sampled, namely Simulium ruficorne, Simulium borbonense and Simulium triplex. The phylogenies based on nuclear and mitochondrial markers showed that S. ruficorne and S. borbonense are the most closely related species. Interestingly, we report a probable mitochondrial introgression between these two species although they diverged almost six million years ago. Finally, we showed that the three Reunion species did not form a monophyletic group, and, combined with the molecular datation, the results indicated that Reunion black fly diversity resulted from multiple colonization events. Thus, multiple colonizations, rather than in-situ diversification, are likely responsible for an important part of black fly diversity found on this young Darwinian island.

El Gran Intercambio Biótico Americano: una revisión paleoambiental de evidencias aportadas por mamíferos y aves neotropicales

Pelegrin, J.S., Gamboa, S., Menendez, I., Hernandez Fernandez, M. 2018. The Great American Biotic Interchange: a paleoecological review considering neotropical mammals and birds. Ecosistemas 27(1): 5-17. Doi.: 10.7818/ECOS.1455 Under classical point of view, the formation of the Panama Isthmus during Pliocene (3 Ma ago) would have allowed the species interchange between North America and South America. This ecological and evolutionary process named Great American Biotic Interchange (GABI) would be determinant in the configuration of the current american biota. This process began to be studied with information from the fossil record in diverse taxa (especially mammals). Furthermore, information from extant species, biogeographic aspects, phylogenetical analysis, a constant growing of fossil record, as well as a significant increase in the geological knowledge of the zone, have allowed us to propose scenarios for a high complexity GABI processes and suggest a scenario of less isolation for South America during the Cenozoic. The most recent evidence derived from studies in birds and mammals point to multiple colonization events since the late Oligocene with the entry of some bird groups, and later along the Miocene with the colonization of lineages in both taxa, these events were previous to what has usually been considered for the interchange process. The fully established GABI is constituted by 4 phases along the Plio-Pleistocene, in each one of them, different waves of colonization were presented between both continents in a great diversity of lineages. Also during Pleistocene-Holocene several processes of extinction were evidenced, the explanation of which were the determining factors in these processes have been cause of debate, this aspect is discussed in our paper, showing through the evidence an important paradigm with explanations based on the relevance of paleogeographic factors and environmental changes in the adaptation processes to biomes. Thus, we leave the classical idea of ecological competition between northern and southern species. In conclusion, the process turns out to be a complex network of biotic interactions conditioned mainly by changing abiotic factors during the paleoenvironmental configuration of the Americas.

Disjunct distribution and distinct intraspecific diversification of Eothenomys melanogaster in South China

BackgroundSouth China encompasses complex and diverse landforms, giving rise to high biological diversity and endemism from the Hengduan Mountains to Taiwan Island. Many species are widely distributed across South China with similar disjunct distribution patterns. To explore the causes of these disjunct distribution patterns and their genetic consequences, we investigated the endemic species Père David’s Chinese Vole (Eothenomys melanogaster) by integrating geological and ecological factors. We analysed the genetic structure and divergence time of E. melanogaster based on fast-evolving mitochondrial and nuclear markers using Bayesian trees and coalescent species tree approaches. Historical scenarios of distribution range and demography were reconstructed based on spatial interpolations of genetic diversity and distance, extended Bayesian skyline plots, phylogeographic diffusion analysis, and ecological niche modelling (ENM) during different periods. We also assessed the relationships between geographical distance/ecological vicariance and genetic distance (isolation by distance, IBD; isolation by environment, IBE).ResultsThe genetic analysis revealed three deeply divergent clades—Southeast, Southwest and Central clades, centred on the Wuyi Mountains, the Yunnan-Guizhou Plateau (YGP) and the mountains around the Sichuan Basin, respectively—that have mostly developed since the Pleistocene. IBD played an important role in early divergence, and geological events (sedimentation of plains and linking of palaeo-rivers) and IBE further reinforced genetic differentiation. ENM shows the importance of suitable habitats and elevations.ConclusionsOur results suggest that the primary cause of the disjunct distribution in E. melanogaster is the high dependence on middle-high-altitude habitat in the current period. Mountains in the occurence range have served as “sky islands” for E. melanogaster and hindered gene flow. Pleistocene climatic cycles facilitated genetic admixture in cold periods and genetic diversification in warm periods for inland clades. During cold periods, these cycles led to multiple colonization events between the mainland and Taiwan and erased genetic differentiation.

Walking backwards into the future: the need for a holistic evolutionary approach in Pacific health research

Context: The Pacific region has had a complex human history. It has been subject to multiple major human dispersal and colonisation events, including some of the earliest Out-of-Africa migrations, the so-called Austronesian expansion of people out of Island Southeast Asia, and the more recent arrival of Europeans. Despite models of island isolation, evidence suggests significant levels of interconnectedness that vary in direction and frequency over time. The Pacific Ocean covers a vast area and its islands provide an array of different physical environments with variable pathogen loads and subsistence opportunities. These diverse environments likely caused Pacific peoples to adapt (both genetically and culturally) in unique ways. Differences in genetic background, in combination with adaptation, likely affect their susceptibility to non-communicable diseases.Objectives: Here we provide an overview of some of the key issues in the natural and human history of the Pacific region which are likely to impact human health. We argue that understanding the evolutionary and cultural history of Pacific peoples is essential for the generation of testable hypotheses surrounding potential causes of elevated disease susceptibility among Pacific peoples.

Ecological preferences of Hyla molleri in the colonisation of arboreal refuges in a human-shaped wetland

Hyla molleri is well adapted to arboreal microhabitats, which are used among breeding seasons. This species is common in wetlands across the Iberian Peninsula and is therefore vulnerable to the loss and degradation of these ecosystems. Due to its secretive habits, the knowledge about the ecology of H. molleri, outside the breeding season, is still scarce. Using artificial refuges as a proxy to natural refuges, we studied how H. molleri uses arboreal microhabitats near reproductive areas and which environmental drivers influence refuge colonisation. We installed 70 PVC pipe refuges in isolated trees and tree patches. Pairs of pipes were installed at two different heights and monitored fortnightly, for four consecutive days, for one year. Each sampling day, we registered the values of variables related with seasonality, microhabitat, dominant plant species, weather and site fidelity. We recorded 2234 individual colonization events by H. molleri, including 516 multiple colonization events, with a maximum of nine individuals in a single refuge. Refuges that were colonized before were more likely to be colonized again. Additionally, colonization was lower in spring and summer and higher in tree clusters than in isolated trees. We found no significant differences on the height or temperature of colonized versus non-colonized refuges. Our results highlight the importance of adequate arboreal microhabitats and the need for the conservation of terrestrial habitats around breeding areas. We also show that artificial refuges can be useful for H. molleri and similar species, namely for habitat improvement or the implementation of citizen-science and monitoring programs.

An early colonisation pathway into northwest Australia 70-60,000 years ago

Colonisation of Sahul 70-60 thousand years ago (kya) represents the first great maritime migration undertaken by anatomically modern humans in one of the final phases of the Out of Africa dispersal. Visual connectivity network analyses, agent-based simulations and ocean current modelling reveal that modern humans could follow numerous northern and southern migration pathways into Sahul. Our results support a southern route out of Africa through South Asia with entry into ISEA through the Banda Arc, culminating in an early colonisation of Sahul on the northwest shelf. Our results show multiple colonisation events through other entry points were also probable, and raise interesting possibilities for complex regional migration and population histories.

Revisiting the genetic diversity and population structure of the critically endangered leatherback turtles in the South-west Atlantic Ocean: insights for species conservation

The worldwide population of the leatherback turtle (Dermochelys coriacea) encompasses seven subpopulations among the Pacific, Atlantic and Indian Oceans. It has experienced declines across parts of its distribution, with the subpopulation of the South-west Atlantic listed as critically endangered by the IUCN Red List. The main threats to this subpopulation include its interaction with fisheries, coastal development, pollution and climate change. In this study, we sequenced mitochondrial DNA from 52 leatherback turtles in Brazil and combined these with published data from other Atlantic Ocean rookeries. The haplotype diversities of the Atlantic population rookeries ranged from 0.112 to 0.533 and are not directly proportional to current rookery sizes. The Brazilian rookery, despite recording low nest numbers per year, had the second-highest haplotype diversity among all Atlantic rookeries (h = 0.532). A mixed-stock analysis revealed that the South American pelagic aggregate is primarily composed of individuals from West Africa (84%), with contributions from the North Atlantic rookeries (14%). Leatherback turtles appear to have a complex phylogeographic pattern, showing evidence of multiple colonization events and a lack of isolation by distance. Our novel dataset, based on DNA sequences of 695 base pairs, will provide baseline data needed to understand population dynamics in the region, building comprehensive population assessments to support and develop management strategies. Having both the only known regular rookery in the South-west Atlantic, and a mixed-origin foraging area for the species along its coast, Brazil has a key role in the conservation of the leatherback turtle.

Ancient connections among the European rivers and watersheds revealed from the evolutionary history of the genus Telestes (Actinopterygii; Cypriniformes).

In order to better understand the complex geologic history of the Mediterranean area, we have analysed evolutionary history, phylogeographic structure and molecular diversity of freshwater fishes belonging to the genus Telestes. As primary freshwater fishes distributed largely in the Mediterranean basin, this genus represents a suitable model system for investigating the historical biogeography of freshwater drainage systems in southern Europe. In this investigation we have included samples representing all Telestes species and based our analyses on one mitochondrial and one nuclear gene. We have investigated phylogenetic structure inside the genus Telestes, estimated divergence times, reconstructed ancestral distribution ranges and described intraspecific molecular diversity. Diversification of Telestes started in the Early Miocene, when the ancestors of T. souffia, lineage comprising T. croaticus and T. fontinalis, and the one comprising T. pleurobipunctatus and T. beoticus got isolated. The remaining species are genetically more closely related and form a common cluster in the recovered phylogenetic trees. Complex geological history of southern Europe, including formation of continental bridges, fragmentation of landmass, closing of the sea corridor, local tectonic activities, led to complicated biogeographical pattern of this genus, caused by multiple colonization events and passovers between ancient rivers and water basins. Especially pronounced diversity of Telestes found in the Adriatic watershed in Croatia and Bosnia and Herzegovina is a consequence of a triple colonization of this area by different lineages, which led to an existence of genetically distinct species in neighboring areas. Significant intraspecific structuring is present in T. souffia, T. muticellus, T. croaticus and T. pleurobipunctatus. Besides in well-structured species, elevated levels of genetic polymorphism were found inside T. turskyi and T. ukliva, as a consequence of their old origin and unconstrained evolutionary history.

Genetic diversity and differentiation patterns in Micromeria from the Canary Islands are congruent with multiple colonization dynamics and the establishment of species syngameons

BackgroundEspecially on islands closer to the mainland, such as the Canary Islands, different lineages that originated by multiple colonization events could have merged by hybridization, which then could have promoted radiation events (Herben et al., J Ecol 93: 572–575, 2005; Saunders and Gibson, J Ecol 93: 649–652, 2005; Caujapé-Castells, Jesters, red queens, boomerangs and surfers: a molecular outlook on the diversity of the Canarian endemic flora, 2011). This is an alternative to the scenario where evolution is mostly driven by drift (Silvertown, J Ecol 92: 168–173, 2004; Silvertown et al., J Ecol 93: 653–657, 2005). In the former case hybridization should be reflected in the genetic structure and diversity patterns of island species. In the present work we investigate Micromeria from the Canary Islands by extensively studying their phylogeographic pattern based on 15 microsatellite loci and 945 samples. These results are interpreted according to the hypotheses outlined above.ResultsGenetic structure assessment allowed us to genetically differentiate most Micromeria species and supported their current classification. We found that populations on younger islands were significantly more genetically diverse and less differentiated than those on older islands. Moreover, we found that genetic distance on younger islands was in accordance with an isolation-by-distance pattern, while on the older islands this was not the case. We also found evidence of introgression among species and islands.ConclusionsThese results are congruent with a scenario of multiple colonizations during the expansion onto new islands. Hybridization contributes to the grouping of multiple lineages into highly diverse populations. Thus, in our case, islands receive several colonization events from different sources, which are combined into sink populations. This mechanism is in accordance with the surfing syngameon hypothesis. Contrary to the surfing syngameon current form, our results may reflect a slightly different effect: hybridization might always be related to colonization within the archipelago as well, making initial genetic diversity to be high to begin with. Thus the emergence of new islands promotes multiple colonization events, contributing to the establishment of hybrid swarms that may enhance adaptive ability and radiation events. With time, population sizes grow and niches start to fill. Consequently, gene-flow is not as effective at maintaining the species syngameon, which allows genetic differentiation and reproductive isolation to be established between species. This process contributes to an even further decrease in gene-flow between species.

The importance of offshore origination revealed through ophiuroid phylogenomics.

Our knowledge of macro-evolutionary processes in the deep sea is poor, leading to much speculation about whether the deep sea is a source or sink of evolutionary adaptation. Here, we use a phylogenetic approach, on large molecular (688 species, 275 kbp) and distributional datasets (104 513 records) across an entire class of marine invertebrates (Ophiuroidea), to infer rates of bathymetric range shift over time between shallow and deep water biomes. Biome conservation is evident through the phylogeny, with the majority of species in most clades distributed within the same bathome. Despite this, bathymetric shifts have occurred. We inferred from ancestral reconstructions that eurybathic or intermediate distributions across both biomes were a transitional state and direct changes between shallow and deep sea did not occur. The macro-evolutionary pattern of bathome shift appeared to reflect micro-evolutionary processes of bathymetric speciation. Results suggest that most of the oldest clades have a deep-sea origin, but multiple colonization events indicate that the evolution of this group conforms neither to a simple onshore-offshore hypothesis, nor the opposite pattern. Both shallow and deep bathomes have played an important role in generating the current diversity of this major benthic class.

Multiple independent colonizations into the Congo Basin during the continental radiation of African Mastacembelus spiny eels

AbstractAimThere has been recent interest in the origin and assembly of continental biotas based on densely sampled species‐level clades, however, studies from African freshwaters are few so that the commonality of macroevolutionary patterns and processes among continental clades remain to be tested. Within the Afrotropics, the Congo Basin contains the highest diversity of riverine fishes, yet it is unclear how this fauna was assembled. To address this, and the diversification dynamics of a continental radiation, we focus on African Mastacembelus spiny eels.LocationAfrotropical freshwaters.MethodsThe most complete molecular phylogeny to date was reconstructed for African spiny eels. Divergence times were estimated applying a Bayesian relaxed clock comparing fossil and geological calibrations across nuclear and mitochondrial trees. Biogeographic reconstructions, applying a dispersal–extinction–cladogenesis model and lineage diversification dynamics were examined.ResultsSpiny eels originated in Asia and colonized Africa c. 15.4 Ma (95% HPD: 23.9–8.8 Ma) from which their subsequent radiation across the Afrotropics was best fitted by a constant rate model. Ancestral state estimation identified multiple colonization events into the Congo Basin, whereas all other regions were likely to have been colonized once indicating considerable geographic constraints. Application of the fossil calibration gave similar age estimates across datasets, whereas a geological calibration estimated considerably older nuclear divergences.Main conclusionsDespite profound environmental events during the evolutionary history of the group, there is no evidence for rapid lineage diversification. This finding supports several recent studies on tropical continental radiations that contrast to the common pattern of density‐dependent diversification. We further show that dispersal has occurred into, as well as out of the Congo Basin, indicating the importance of this region in the generation of biodiversity.

A new anchialine Stephos Scott from the Yucatan Peninsula with notes on the biogeography and diversity of the genus (Copepoda, Calanoida, Stephidae).

Surveys of the anchialine crustacean fauna of the Yucatan Peninsula (YP), Mexico, have revealed the occurrence of calanoid copepods. The genus Stephos Scott, 1892, belonging to the family Stephidae is among the most frequent and widely distributed groups in anchialine caves but has not been hitherto recorded from the YP. Recent collections from an anchialine cave in an island off the northern coast of the YP yielded many specimens of a new species of Stephos. The new taxon, S. fernandoi sp. n., is described here based on male and female specimens. The new species is clearly distinguished from its congeners by the following characters: male left fifth leg with three terminal lamellae plus subdistal process, right leg with distal row of peg-like elements; female fifth leg with single long, acute apical process; genital double-somite with two rows each of 4 long spinules adjacent to operculum; legs 2-4 with articulated setae. The diversity of the genus shows regional differences; the Australia-Western Pacific region is the most diverse (eleven species), followed by the Mediterranean (seven species) and the Northeastern Atlantic (six species); only four species are known from the Northwestern Tropical Atlantic (NWTA). The morphology of the female fifth leg was examined to explore possible biogeographic trends in the genus; patterns suggest multiple colonization events in the highly diverse regions and a relatively recent radiation in the NWTA, characterized by anchialine forms. The introduction of stephid copepods in the region may be a relatively recent event derived from colonization of benthopelagic ancestral forms and subsequent invasion onto cave habitats. The new species appears to be linked to the strictly anchialine Miostephos.

Haplotype diversity of mtCOI in the fall webworm Hyphantria cunea (Lepidoptera: Arctiidae) in introduced regions in China, Iran, Japan, Korea, and its homeland, the United States

Hyphantria cunea (Drury) has colonized many countries outside its native range of North America and has become a model species for studies of the colonization and subsequent adaptation of agricultural pests. Molecular genetic analyses can clarify the origin and subsequent adaptations to non-native habitats. Using the mitochondrial COI gene, we examined the genetic relationships between invasive populations (China, Iran, Japan, and Korea) and native populations (i.e., the United States). The Jilin (China) and Guilan (Iran) populations showed nine previously unknown haplotypes that differed from those found in the south–central United States, suggesting multiple colonization events and different regions of invasion. A dominant mtDNA haplotype in populations in the United States was shared by all of the populations investigated, suggesting that H. cunea with that haplotype have successfully colonized China, Iran, Japan, and Korea.

Redescription and Molecular Assessment of Relationships Among Three Species of Echeneibothrium (Rhinebothriidea: Echeneibothriidae) Parasitizing the Yellownose Skate, Dipturus chilensis, in Chile.

Much progress has recently been made in revising the taxonomic assignments of genera originally classified in the polyphyletic "Tetraphyllidea." Many of these genera, including Echeneibothrium, were accommodated in the order Rhinebothriidea. However, beyond this larger taxonomic action, little work has been conducted on this genus over the past 50 yr. Consequently, the criteria used for characterizing species of Echeneibothrium have lagged behind those typically used in more modern descriptions of elasmobranch-hosted cestode taxa. A series of collecting trips to Chile to obtain cestodes from the yellownose skate, Dipturus chilensis , provided a unique opportunity to apply modern morphological and molecular methods to investigate the 3 species of Echeneibothrium reported parasitizing this skate, specifically Echeneibothrium megalosoma, Echeneibothrium multiloculatum, and Echeneibothrium williamsi. In addition to redescribing all 3 species, using morphological data from light and scanning electron microscopy, maximum likelihood and bayesian inference phylogenetic analyses of the D1-D3 regions of the 28S rDNA gene were conducted to assess their relationships among other echeneibothriids for which comparable data are available. Sequencing of 59 specimens representing these 3 species of Echeneibothrium allowed us to assess the intra- and interspecific variation in the 28S rDNA gene. The redescriptions use standardized terminology for scolex morphology, proglottid anatomy, and microthrix forms and pattern; they also expand on the original descriptions to include data on scolex size, ovary size, vas deferens and vaginal configurations, testes arrangement, and genital pore position. Our morphological work led to a major reinterpretation of the scolex morphology with the recognition that all 3 species bear an apical bothridial sucker, rather than an apical loculus, prompting emendation of the diagnosis for the family Echeneibothriidae. The presence of a band of spinitriches at the apex of the apical modification of the scolex proper seems to represent an important feature for distinguishing the 2 portions of the myzorhynchus across species. Intraspecific variation ranged from 0 to 7 bp across species and interspecific variation ranged from a low of 39-46 bp between E. williamsi and E. multiloculatum to a high of 61-66 bp between E. multiloculatum and E. megalosoma. Phylogenetic analyses indicate that the 3 species of Echeneibothrium hosted by the yellownose skate are not each other's closest relatives, suggesting multiple colonization events of D. chilensis have occurred. Further phylogenetic investigation is also likely to confirm the status of the genus Pseudanthobothrium as a synonym of Echeneibothrium because its species generally group among members of Echeneibothrium.

Understanding influences of culture and history on mtDNA variation and population structure in three populations from Assam, Northeast India.

Positioned at the nexus of India, China, and Southeast Asia, Northeast India is presumed to have served as a channel for land-based human migration since the Upper Pleistocene. Assam is the largest state in the Northeast. We characterized the genetic background of three populations and examined the ways in which their population histories and cultural practices have influenced levels of intrasample and intersample variation. We examined sequence data from the mtDNA hypervariable control region and selected diagnostic mutations from the coding region in 128 individuals from three ethnic groups currently living in Assam: two Scheduled tribes (Sonowal Kachari and Rabha), and the non-Scheduled Tai Ahom. The populations of Assam sampled here express mtDNA lineages indicative of South Asian, Southeast Asian, and East Asian ancestry. We discovered two completely novel haplogroups in Assam that accounted for 6.2% of the lineages in our sample. We also identified a new subhaplogroup of M9a that is prevalent in the Sonowal Kachari of Assam (19.1%), but not present in neighboring Arunachal Pradesh, indicating substantial regional population structuring. Employing a large comparative dataset into a series of multidimensional scaling (MDS) analyses, we saw the Rabha cluster with populations sampled from Yunnan Province, indicating that the historical matrilineality of the Rabha has maintained lineages from Southern China. Assam has undergone multiple colonization events in the time since the initial peopling event, with populations from Southern China and Southeast Asia having the greatest influence on maternal lineages in the region.

Alpine lakes and ponds – a promising source of high genetic diversity in metapopulations of aquatic insects

Alpine lakes and ponds are unique and vulnerable aquatic habitats inhabited by specific species assemblages. In contrast to alpine streams, the genetic diversity and population structure of the organisms found in alpine standing waters are almost completely unknown. Here we present a population genetic study of a macroinvertebrate species from alpine lakes, the diving beetle Agabus bipustulatus (Linnaeus, 1767). We used partial cytochrome b (Cyt b) mtDNA gene of 560 specimens from 43 lakes and ponds distributed across 20 mountain valleys of the Tatra Mountains (Western Carpathians) and their foothills. The aims of this study were to provide detailed genetic metapopulation analysis of A. bipustulatus within a geographically small mountain system, to explore the role of ridges in isolating lake populations, and to test for the applicability of Cyt b in insect population genetic studies. We detected high genetic variability (42 haplotypes), comparable to many large spatial scale studies. There was a star-shaped genetic structure with few dominant haplotypes, which confirmed recent origin, rapid expansion of metapopulation, and multiple colonization of the Tatra Mountain region by A. bipustulatus. The populations within the mountain system differed from each other, suggesting that the Tatra Mountain lakes and ponds were colonized through multiple colonization events, and also that colonization of the region and evolution of metapopulations are to a certain extent influenced by ridge barriers.

Recent studies overestimate colonization and extinction events for Adelie Penguin breeding colonies

ABSTRACT Modeling metapopulation dynamics is potentially a useful and powerful tool for ecologists and conservation biologists. However, the key processes driving metapopulation dynamics are colonization and extinction events, which are notoriously difficult to study. A recent global assessment of Adelie Penguin (Pygoscelis adeliae) breeding populations reported multiple potential colonization and extinction events from occupancy observations using recent high-resolution satellite imagery and examination of historical occupancy literature, but emphasized that the events should be confirmed with direct observations. We evaluated these conclusions by developing a comprehensive database of direct observations of Adelie Penguin breeding site occupancy across East Antarctica. The database allowed 16 of 19 proposed colonization and extinction events in this region to be evaluated using direct observations that were concurrent in space and time (same breeding season) with observations from satellite imagery. We ...

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.

A molecular phylogeny of Pseudocrangonyx from Japan, including a new subterranean species (Crustacea, Amphipoda, Pseudocrangonyctidae)

A subterranean species of pseudocrangonyctid amphipod, Pseudocrangonyx gudariensis Tomikawa & Sato, sp. n., is described from the spring-fed stream Gudari-numa in Hakkoda Mountains, Aomori Prefecture, northern Japan. Pseudocrangonyx gudariensis is morphologically similar to P. coreanus Uéno, 1966 and P. febras Sidorov, 2009 based on its relatively small body size, small number of articles of rami of pleopods, and urosomite 1 without basal setae. However, P. gudariensis is distinguished from those species based on the following characteristics: from P. coreanus, antenna 2 of female without calceoli, palmar margins of gnathopods 1 and 2 with distally notched robust setae, inner margin of inner ramus of uropod 2 with 4 robust setae, and basal part of inner ramus of uropod 2 without slender seta; and from P. febras, carpus of gnathopod 2 without serrate robust setae on posterodistal corners, peduncle of pleopods 1 and 2 with setae, and longer article 2 of uropod 3. Phylogenetic analyses using nuclear 28S rRNA and histone H3, and mitochondrial cytochrome c oxidase subunit I and 16S rRNA markers showed that P. gudariensis is placed among known Pseudocrangonyx Akatsuka and Komai, 1922 species. However, its exact phylogenetic position within the genus could not be determined. The polyphyly of the Japanese Pseudocrangonyx species indicates that multiple colonization events of Pseudocrangonyx ancestors to the Japanese Archipelago could have occurred. The reliability of the past Pseudocrangonyx records from Japan is briefly discussed.

Multiple colonisations of the Lake Malawi catchment by the genus Opsaridium (Teleostei: Cyprinidae)

It has been proposed that the fish faunas of African rivers assemble through multiple colonisation events, while lake faunas form additionally through intralacustine speciation. While this pattern has been established for many lineages, most notably cichlids, there are opportunities to further investigate the concept using phylogenies of congeneric endemic species within ancient lake catchments. The Lake Malawi catchment contains three river-spawning cyprinids of the genus Opsaridium, two of which are endemic. These species differ in body size, migratory behaviour and habitat use, but it has never previously been tested if these represent a monophyletic radiation, or have instead colonised the lake independently. We placed these species in a broader phylogeny of Opsaridium and the related genus Raiamas, including all known species from the river systems surrounding Lake Malawi. Our results suggest that each of the species has independently colonised the lake catchment, with all three taxa having well-defined sister taxa outside of the lake, and all sharing a common ancestor ∼14.9million years ago, before the Lake Malawi basin started to form ∼8.6million years ago. Additionally, the results strongly support previous observations that Opsaridium is not a monophyletic group, but instead contains Raiamas from the Congo drainage. Together these results are supportive of the concept that river fish faunas within African catchments are primarily assembled through a process of accumulation from independent origins, rather than within-catchment speciation and adaptive radiation. In light of these results we also suggest there is scope for a re-evaluation of systematics of both Opsaridium and Raiamas.