Dispersal History Research Articles

Lakhuti-IV – A new site of the early Palaeolithic in Central Asia (Tajikistan)

Opening of series of sites of Loess Palaeolithic in Central Asia, found within a different levels of loess-palaeosol sequences of Tajikistan, was a great step in understanding history of hominin dispersal in Eurasia. The highest density of Loessic Palaeolithic sites is recorded in the Khovaling Loess Plateau. In 2021 a Russian-Tajik geoarchaeological expedition carried out an archaeological survey and discovered an area rich in stone artefacts, concentrated in pedocomplexes 5, which was excavated and called Lakhuti-IV. All archaeological material at the Lakhuti-IV site was associated with pedocomplex 5, consisting of two well developed palaeosols reflecting different climatic phases of the interglacial period. The stratigraphic occurrence and the typological characteristics of the assemblage indicate a single industry. Several knapping technologies are recorded in the primary knapping: radial, slice and simple parallel. From the existing geochronological data for the Khovaling Loess Plateau, cultural layer of Lakhuti-IV is correlated with MIS 13 (∼0.5 Ma). A distinctive feature of Lakhuti-IV, and one which distinguishes it from the entire assemblages of the Palaeolithic sites in the Khovaling Loess Plateau, is the high concentration of artefacts. Another unique feature of the site is that here, for the first time in the Loessic Palaeolithic of Central Asia artefacts are found in several distinct cultural horizons within the same pedocomplex, i.e., within the same climatic warm period.

The evolutionary history of bees in time and space

Bees are the most significant pollinators of flowering plants. This partnership began ca. 120 million years ago, but the uncertainty of how and when bees spread across the planet has greatly obscured investigations of this key mutualism. We present a novel analysis of bee biogeography using extensive new genomic and fossil data to demonstrate that bees originated in Western Gondwana (Africa and South America). Bees likely originated in the Early Cretaceous, shortly before the breakup of Western Gondwana, and the early evolution of any major bee lineage is associated with either the South American or African land masses. Subsequently, bees colonized northern continents via a complex history of vicariance and dispersal. The notable early absences from large landmasses, particularly in Australia and India, have important implications for understanding the assembly of local floras and diverse modes of pollination. How bees spread around the world from their hypothesized Southern Hemisphere origin parallels the histories of numerous flowering plant clades, providing an essential step to studying the evolution of angiosperm pollination syndromes in space and time.

Persistent effects of historical sea levels on the population structure of a temporary wetland copepod

Abstract Temporary wetland ecosystems are common in arid and semi‐arid environments, and are inhabited by diverse invertebrate communities. Little is known about the dynamics of genetic connectivity in the geographically scattered populations of these wetland specialists. The current study investigated the spatial genetic structure and dispersal history of a recently described calanoid copepod, Lovenula raynerae, reported from temporary wetlands in the Eastern Cape province of South Africa. We tested whether the species represents a single, well‐connected population or comprises different regional genetic groups, some of which may be rare or endangered. Mitochondrial COI sequences were generated for 365 specimens from 46 temporary wetlands spread across the species' known distribution range. Isolation‐by‐distance and isolation‐by‐environment patterns of partitioning genetic variations across the landscape were evaluated. In addition, the presence of historical impediments to gene flow between contemporary populations was investigated using a combination of Monmonier's algorithm and Bayesian reconstruction of phylogeographical diffusion in continuous space. The wetland populations were highly structured across the landscape and could be assigned to six distinct evolutionary lineages, potentially representing some level of cryptic speciation. Two distinct phases were identified in the dispersal history of these lineages. Initially, dispersal only occurred inland of a postulated barrier, but eventually the barrier disappeared and the species extended its range by spreading into regions close to the coastline. Molecular dating shows that the barrier represents the upper limit of the coastline during the Pliocene, and that its crossing was facilitated by Pliocene sea regression in southern Africa. Our finding shows that complex demographic histories can be preserved in the mitochondrial DNA of temporary wetland crustaceans because of limited effective gene flow after initial colonisation events. This makes them an interesting study system to explore the long‐term effects of climate change on arid ecosystem communities.

Plastome phylogenomics reveals an early Pliocene North- and Central America colonization by long-distance dispersal from South America of a highly diverse bromeliad lineage.

Understanding the spatial and temporal frameworks of species diversification is fundamental in evolutionary biology. Assessing the geographic origin and dispersal history of highly diverse lineages of rapid diversification can be hindered by the lack of appropriately sampled, resolved, and strongly supported phylogenetic contexts. The use of currently available cost-efficient sequencing strategies allows for the generation of a substantial amount of sequence data for dense taxonomic samplings, which together with well-curated geographic information and biogeographic models allow us to formally test the mode and tempo of dispersal events occurring in quick succession. Here, we assess the spatial and temporal frameworks for the origin and dispersal history of the expanded clade K, a highly diverse Tillandsia subgenus Tillandsia (Bromeliaceae, Poales) lineage hypothesized to have undergone a rapid radiation across the Neotropics. We assembled full plastomes from Hyb-Seq data for a dense taxon sampling of the expanded clade K plus a careful selection of outgroup species and used them to estimate a time- calibrated phylogenetic framework. This dated phylogenetic hypothesis was then used to perform biogeographic model tests and ancestral area reconstructions based on a comprehensive compilation of geographic information. The expanded clade K colonized North and Central America, specifically the Mexican transition zone and the Mesoamerican dominion, by long-distance dispersal from South America at least 4.86 Mya, when most of the Mexican highlands were already formed. Several dispersal events occurred subsequently northward to the southern Nearctic region, eastward to the Caribbean, and southward to the Pacific dominion during the last 2.8 Mya, a period characterized by pronounced climate fluctuations, derived from glacial-interglacial climate oscillations, and substantial volcanic activity, mainly in the Trans-Mexican Volcanic Belt. Our taxon sampling design allowed us to calibrate for the first time several nodes, not only within the expanded clade K focal group but also in other Tillandsioideae lineages. We expect that this dated phylogenetic framework will facilitate future macroevolutionary studies and provide reference age estimates to perform secondary calibrations for other Tillandsioideae lineages.

Genomics reveal the origins and current structure of a genetically depauperate freshwater species in its introduced Alaskan range.

Invasive species are a major threat to global biodiversity, yet also represent large-scale unplanned ecological and evolutionary experiments to address fundamental questions in nature. Here we analyzed both native and invasive populations of predatory northern pike (Esox lucius) to characterize landscape genetic variation, determine the most likely origins of introduced populations, and investigate a presumably postglacial population from Southeast Alaska of unclear provenance. Using a set of 4329 SNPs from 351 individual Alaskan northern pike representing the most widespread geographic sampling to date, our results confirm low levels of genetic diversity in native populations (average 𝝅 of 3.18 × 10-4) and even less in invasive populations (average 𝝅 of 2.68 × 10-4) consistent with bottleneck effects. Our analyses indicate that invasive northern pike likely came from multiple introductions from different native Alaskan populations and subsequently dispersed from original introduction sites. At the broadest scale, invasive populations appear to have been founded from two distinct regions of Alaska, indicative of two independent introduction events. Genetic admixture resulting from introductions from multiple source populations may have mitigated the negative effects associated with genetic bottlenecks in this species with naturally low levels of genetic diversity. Genomic signatures strongly suggest an excess of rare, population-specific alleles, pointing to a small number of founding individuals in both native and introduced populations consistent with a species' life history of limited dispersal and gene flow. Lastly, the results strongly suggest that a small isolated population of pike, located in Southeast Alaska, is native in origin rather than stemming from a contemporary introduction event. Although theory predicts that lack of genetic variation may limit colonization success of novel environments, we detected no evidence that a lack of standing variation limited the success of this genetically depauperate apex predator.

Geological events and climate change drive diversification and speciation of mute cicadas in eastern continental Asia

The poor mobility of nymphs living underground, usually for many years, and the weak flying ability of adults make cicadas unique for evolutionary biology and bio-geographical study. Cicadas of the genus Karenia are unusual in Cicadidae in lacking the timbals that produce sound. Population differentiation, genetic structure, dispersal and evolutionary history of the eastern Asian mute cicada Karenia caelatata were investigated based on morphological, acoustic and molecular data. The results reveal a high level of genetic differentiation in this species. Six independent clades with nearly unique sets of haplotypes corresponding to geographically isolated populations are recognized. Genetic and geographic distances are significantly correlated among lineages. The phenotypic differentiation is generally consistent with the high levels of genetic divergence across populations. Results of ecological niche modeling suggest that the potential distribution range of this mountain-habitat specialist during the Last Glacial Maximum was broader than its current range, indicating this species had benefited from the climate change during the early Pleistocene in southern China. Geological events such as orogeny in Southwest China and Pleistocene climate oscillations have driven the differentiation and divergence of this species, and basins, plains and rivers function as natural “barriers” to block the gene flow. Besides significant genetic divergence being found among clades, the populations occurring in the Wuyi Mountains and the Hengduan Mountains are significantly different in the calling song structure from other populations. This may have resulted from significant population differentiation and subsequent adaptation of related populations. We conclude that ecological differences in habitats, coupled with geographical isolation, have driven population divergence and allopatric speciation. This study provides a plausible example of incipient speciation in Cicadidae and improves understanding of population differentiation, acoustic signal diversification and phylogeographic relationships of this unusual cicada species. It informs future studies on population differentiation, speciation and phylogeography of other mountain-habitat insects in the East Asian continent.

Enhanced sampling refines the biogeography of the freshwater green alga Aegagropila linnaei (Cladophoraceae)

ABSTRACT A phylogeographic approach is the only way to study the dispersal history of most algae, which are rarely preserved as fossils. However, the only freshwater alga for which this approach has been applied on a Eurasian scale is the endangered green alga Aegagropila linnaei, which is thought to be a poor disperser. Previous phylogeographic results were explained by stepwise dispersal across the Holarctic from an ancestral area in Japan, with further survival in European ice-dammed glacial lakes and extinction in continental Siberia, which lacks such refugia. To clarify the biogeography of A. linnaei in Eurasia we supplemented the published data on its ribotype (internal transcribed spacer of ribosomal DNA) distribution with data from previously unexplored East Europe, Mongolia and the Russian Far East. We have found two new ribotypes, one scattered across temperate Europe and another confined to one locality in the north-eastern Russian Far East. We also expanded the distribution of a ribotype previously reported from Scotland and continental West Europe to include East Europe, Iceland and Central Mongolia. Phylogeogeographic approach based on enhanced sampling allowed us to refine the biogeography of A. linnaei. We discuss reasons for underestimation of A. linnaei dispersal potential. A focused inventory of A. linnaei will likely reveal new localities of the species enabling a further improvement in biogeographical reconstructions. Area-wide studies of other freshwater algae in Eurasia need to be performed to test the generality of the revealed biogeographical patterns.

Phylogeny, Distribution, and Biology of Pygmy Whitefish (Prosopium coulterii) in the Beringia Region (Chukotka)

The pygmy whitefish Prosopium coulterii (C. H. Eigenmann & R. S. Eigenmann, 1892) is a freshwater fish with a highly disjunct distribution ranging from the middle part of North America to Chukotka. There is still no consensus regarding its phylogeny and dispersal history due to limited information from the Chukotkan part of the range. We investigated 22 lakes over Chukotka and found a much broader distribution than it was previously thought. Pygmy whitefish was found to be a common species in the lakes that belong to rivers draining into the Arctic. Cytochrome B, cytochrome oxidase subunit 1, and ATP synthase F0 subunit 6 mitochondrial sites were analyzed from 25 samples to reconstruct the phylogenetic history of pygmy whitefish. Two haplogroups belonging to the east and west Chukotkan ranges were identified; both groups are closely related to Alaskan pigmy whitefish and distant from the Cascadia-Mackenzie (Peace) populations. Combining the distribution patterns, phylogenetic network topology, and the contemporary knowledge on the glaciation history of the region, we suggest a possible colonization pathway over Beringia region and beyond it. The basic biological characteristics (fork length, number of gill rakers, and pyloric caeca, age structure, and feeding) are also presented to characterize the populations over the investigated range.

Herodotools: An R package to integrate macroevolution, biogeography and community ecology

AbstractAimSpeciation, extinction and historical dispersal are the ultimate factors generating and maintaining biodiversity. However, methods of macroevolution used to detect historical processes usually ignore the variation of macroevolutionary processes at scales finer than entire regions. Likewise, biogeography and community ecology often ignore deep‐time evolutionary processes. To overcome this problem, it is necessary to integrate data from ancestral state reconstructions, current species distributions and biogeographical regionalization. Herodotools is an R package designed to perform this integration.LocationGlobal application, with an example from Neotropics.Major taxa studiedAny taxa, with an example from small rodents (genus Akodon and subfamily Sigmodontinae).MethodsHerodotools streamline analyses of historical biogeography, including regionalization, calculation of assemblage age, lineage in situ diversification and community phylogenetic metrics, merging species occurrence with macroevolutionary methods of ancestral area and trait reconstruction. The main functions of our R package are presented with toy examples and by analysing the historical biogeography of small rodent assemblages in the Neotropics.ResultsOur package can integrate methods from biogeography, macroevolution and community ecology, allowing us to downscale the effects of historical processes and calculate important historical variables (e.g., age of assemblages, in situ diversification, phylogenetic regionalization, phylogenetic transition zones, metrics of trait macroevolutionary dynamics and new metrics of phylogenetic diversity and endemism) in different scales, from entire regions to communities of co‐occurrent species.Main ConclusionsHerodotools is the first platform to streamline the analysis of historical biogeography, enabling a better understanding of historical processes at different levels of organization, from local assemblages to entire biogeographical regions and incorporating macroevolutionary models in commonly used community phylogenetic metrics. This integration bridges the gap between macroevolutionary, biogeography and community ecology methods.

The Movement Ecology of Mutualism (CSEE/ESA 2022, OOS17)

The Movement Ecology of Mutualism (<scp>CSEE</scp>/<scp>ESA</scp> 2022, <scp>OOS17</scp>)

Phylogenetic divergence associated with climate oscillations and topology illustrates the dispersal history of Formosan sambar deer (Rusa unicolor swinhoii) in Taiwan

The island of Taiwan represents an ideal context for studying the effects of climatic oscillations and topographic variation on large herbivores due to its varied tropical to sub-tropical climate zones at different elevational ranges. We explored the phylogenetics of Formosan sambar deer (Rusa unicolor swinhoii) using the control region of the mitochondrial genome. We detected 18 haplotypes among 454 sequences across the island and grouped them into six regions based on SAMOVA, with 68.78% variance among regions. A Bayesian phylogenetic dendrogram revealed two spatially segregated genetic clades. Neutrality tests and Bayesian skyline plots uncovered different demographic expansion histories for the two clades. We further tested divergence times and chronology to propose potential phylogenetic scenarios, which were examined using approximate Bayesian computation. Finally, we present a credible hypothesis for a glacial refugium in the northern part of the Central Mountain Range. Subsequent secondary contact between the two clades during interglacial periods has led to the extant genetic structure of Formosan sambar deer.

Model misspecification misleads inference of the spatial dynamics of disease outbreaks

Epidemiology has been transformed by the advent of Bayesian phylodynamic models that allow researchers to infer the geographic history of pathogen dispersal over a set of discrete geographic areas [1, 2]. These models provide powerful tools for understanding the spatial dynamics of disease outbreaks, but contain many parameters that are inferred from minimal geographic information (i.e., the single area in which each pathogen was sampled). Consequently, inferences under these models are inherently sensitive to our prior assumptions about the model parameters. Here, we demonstrate that the default priors used in empirical phylodynamic studies make strong and biologically unrealistic assumptions about the underlying geographic process. We provide empirical evidence that these unrealistic priors strongly (and adversely) impact commonly reported aspects of epidemiological studies, including: 1) the relative rates of dispersal between areas; 2) the importance of dispersal routes for the spread of pathogens among areas; 3) the number of dispersal events between areas, and; 4) the ancestral area in which a given outbreak originated. We offer strategies to avoid these problems, and develop tools to help researchers specify more biologically reasonable prior models that will realize the full potential of phylodynamic methods to elucidate pathogen biology and, ultimately, inform surveillance and monitoring policies to mitigate the impacts of disease outbreaks.

Variability of the Gene Cytochrome &lt;i&gt;b&lt;/i&gt; mtDNA of the Tundra Vole (&lt;i&gt;Alexandromys oeconomus&lt;/i&gt; Pallas, 1776) in North-Eastern Asia and Alaska

The nucleotide sequence polymorphism and haplotype diversity of the cytochrome b gene in samples of the tundra vole (Alexandromys oeconomus) from North-Eastern Asia and Alaska were studied. 63 haplotypes of cytb gene (51 variants of Central Asian and 12 of Beringian genetic lineages), differing among themselves by 94 mutations, were found. The Upper Kolyma River is inhabited by voles of the Central Asian clade. Mixed population of this species in the basin of the Omolon River (right tributary of the Kolyma River) was found. In Chukotka and Alaska, only specimens of the Beringian phylogroup were found. Genetic differences between all samples are statistically significant. Genetic data of A. oeconomus populations of the Kolyma River basin, Alaska, and Northern Okhotomorye were compared. A total of 231 substitutions in 226 sites were found in the nucleotide sequence of cytochrome b mtDNA gene in voles from both clades. The values of molecular diversity indices testify to the stability of populations with a high value of effective abundance over a long period of time. An analysis of population gene pool formation was performed and a proposed reconstruction of the complex dispersal history of this species across North-Eastern Asia was proposed.

New Records of the Alien Chinese Ricefish (Oryzias sinensis) and Its Dispersal History across Eurasia

The diversity of biota in different parts of the planet has demonstrated dramatic changes within the last several decades due to the extinction of native taxa and the appearance of invasive taxa. The correct taxonomic identification of non-native species is important for understanding their dispersal abilities, especially when potential invaders may be of closely related species. Information on the species identity of ricefish (Oryzias spp.), which have formed self-sustainable populations in some parts of Eurasia, is contradictory. In this paper, we studied samples from non-native populations of Oryzias from several Eurasian regions. The results of our mtDNA COI partial sequence study confirm that the individuals we studied belong to the species Chinese ricefish, O. sinensis. Analyses of the literature and our own data suggest that all known alien populations of Oryzias in continental Eurasia belong to the same species, O. sinensis. A recent finding of O. sinensis in the Don delta suggests that one of the species’ secondary dispersal pathways could run from the Kuban region through the lower part of the Don basin to the Cis-Azov area.

Per-Simper, An Innovative Method for Identifying Community Assembly Processes Within Modern, Recent, and Deep-Time Paleontological Assemblages

How biological communities are assembled is an old but lively debate, especially today, as the efficiency of conservation policies depend on our capacity to correctly identify the assembly processes at play within the species assemblages we aim to protect. The wide range of assembly modes, once seen as mutually exclusive hypothesis are now seen as part of a continuum where the opposite ends correspond to niche- and dispersal-assembly perspectives. Niche-assembled communities are closed and balanced with a stable taxonomic composition depending on deterministic processes when dispersal-assembled communities are open, in non-equilibrium state with constantly changing compositions depending on historical process and continuous dispersion between communities. The former must be protected by increasing habitat diversity and heterogeneity when the latter needing high connectivity to ensure dispersal between habitats. Protecting modern at-risk communities will require an understanding of how assembly processes have been affected by past climate change (both recent and ancient) or by the historical exploitation of ecosystems by humans. However, few methods exist that are capable of identifying assembly processes within paleontological datasets and producing time series at multiple scales due to missing information in the vast majority of the fossil record (e.g., abundance, environmental information, highly-resolved phylogeny) or due to limited precision of compatible methods (i.e. random vs. non-random patterns). The new PER-SIMPER method (and its associated DNCImper R package) can be used to identify and quantify the respective roles of niche and dispersal processes from the distribution of occurrences of extinct and extant species. Based on three modes of permutation of the occurrence matrix, I will illustrate PER-SIMPER with deep-time (e.g., trilobites), ancient (e.g. Cenozoic mammals) and modern datasets (e.g. small mountain mammals, host-flea assemblages).

There and Back Again: The Unexpected Journeys of Metridium de Blainville, 1824 between the Old Oceans and throughout the Modern World.

AbstractMembers of the sea anemone genus Metridium are abundant in temperate rocky habitats and fouling communities. Their biogeographic history is expected to reflect changes in currents and habitats that have influenced benthic communities, such as the climate-influenced changes that occurred during the Last Glacial Maximum. More recently, however, anthropogenic influences such as shipping transportation and the creation of artificial habitat have altered and affected the composition of modern-day marine communities. Here we use sequence-capture data to examine the genetic structure of Metridium across its shallow-water distribution to (1) evaluate species boundaries within Metridium, (2) elucidate the dispersal history of Metridium between and among oceans, and (3) assess the influence of anthropogenic movement on modern-day populations. We find strong evidence for two species within Metridium: M. farcimen and M. senile. Dispersal from the Pacific to the Atlantic included a subsequent isolation of a small population in or above the Bering Sea, which has presumably moved southward. Within the native range of M. senile, admixture is prevalent even between oceans as a result of anthropogenic activities. The nonnative populations in Chile and the Falkland Islands came from at least two distinct introduction events originating from both coasts of the United States in the North Pacific and North Atlantic Oceans. Hybridization between M. senile and M. farcimen is documented as occurring in anthropogenically influenced habitats. The heavy influence from anthropogenic activities will continue to impact our understanding of marine organisms, particularly within the native range and for those that are easily transported across long distances.

Revisiting species delimitation within Reithrodontomys sumichrasti (Rodentia: Cricetidae) using molecular and ecological evidence

Reithrodontomys sumichrasti is distributed from central México to Panama. Previous studies using DNA sequences suggest the existence of distinct clades that may deserve species-level recognition. Here, we use multiple methods of species delimitation to evaluate if this taxon is a complex of cryptic species. DNA sequences from the genes Cyt-b, Fgb-I7, and Acp5 were obtained from GenBank to perform molecular analyses. Species boundaries were tested using the bGMYC, STACEY, and BPP species delimitation methods. Divergence times were estimated as well as the Cyt-b genetic distances. We developed Ecological Niche Models and tested hypotheses of niche conservatism. Finally, we estimated the spatiotemporal history of lineage dispersal. The bGMYC proposed two species while STACEY and BPP proposed 4 species (genetic distances ranged from 5.43 % to 7.52 %). The ancestral position of clade I was recovered, with a Pleistocene diversification time within R. sumichrasti at ~2.15 Ma. For clade pairwise niche comparisons, the niche identity hypothesis was rejected. The ancestral distribution of R. sumichrasti was centered in Central America and spread to the west crossing the Isthmus of Tehuantepec and extending to the mountain regions of Central México. Our taxonomic considerations included the recognition of four clades as distinct species within R. sumichrasti.

Genetic relationships among populations of the small Indian mongoose (Urva auropunctata) introduced in Japan

The small Indian mongoose, Urva auropunctata, is one of the most notorious invasive species in the world. In Japan, the mongoose was introduced to Amami, Kyushu (Kiire region), and Okinawa Islands. Currently, an eradication program for the Amami population is proving successful. To prevent reinvasion and conserve biodiversity, it would be advantageous to investigate the origin and dispersal history of introduced mongoose populations in Japan. We determined the mitochondrial genome of a mongoose from the Okinawa population and confirmed that the systematic status of the mongoose is Urva auropunctata. We also found two haplotypes of cytochrome b in the Amami population, one of which is common among the Okinawa, Amami, and Kiire populations. Based on our microsatellite analysis, the three populations were genetically different from each other. Furthermore, with a low pairwise FST value, the Kiire population was closer to the Okinawa than the Amami population. Our results suggest that the Okinawa population could be the source of the Amami and Kiire populations. These results align with historical records of mongoose in Japan and clarify its genetic status. Our results should aid the prediction of the pathway through which a new invasion will likely occur.

Systematic headwater sampling of white‐spotted charr reveals stream capture events across dynamic topography

AbstractAimRiver system rearrangements such as stream capture play a crucial role in determining range expansion and gene flow of stream organisms between different watersheds. However, it is challenging to clarify the role of stream capture in dynamic landscapes where frequent connections and disconnections occur in stream networks. We hypothesized that fine‐scale sampling with genome‐wide analysis could reveal the effect of stream capture on the range expansion of stream fish and detect unidentified river rearrangement of headwater streams in a highly heterogeneous landscape.LocationHonshu Island, Japan.Taxon Salvelinus leucomaenis. MethodsTo identify stream capture events from biological evidence, a sampling strategy was designed with fish collected from multiple pairs of adjacent headwater streams. This included a ‘typical site’ where the occurrence of a stream capture event has been confirmed with geological evidence. The genetic population structure was analysed using genome‐wide single nucleotide polymorphism (SNP) data using MIG‐seq, followed by a Bayesian clustering approach.ResultsEvidence was found for historical dispersal across watersheds, including a typical stream capture site. This cross‐drainage dispersal promoted gene flow among the three genetic groups of focal fish inhabiting western Honshu Island. The likelihood of past stream capture increased substantially when the inter‐headwater distance was less than 2000 m, or the altitudinal difference was less than 200 m in the current topography.Main ConclusionsIn highly dynamic areas, such as the study site, which is surrounded by active faults, stream capture may be frequent, and aids inter‐drainage dispersal of freshwater organisms, where large‐scale range expansions would otherwise be impossible. Systematic pairwise headwater sampling, together with genome‐wide SNP analysis, provides biological evidence for the history of water system rearrangements and enables the identification of geological events.

Historical dispersal and host-switching formed the evolutionary history of a globally distributed multi-host parasite – The Ligula intestinalis species complex

Studies on parasite biogeography and host spectrum provide insights into the processes driving parasite diversification. Global geographical distribution and a multi-host spectrum make the tapeworm Ligula intestinalis a promising model for studying both the vicariant and ecological modes of speciation in parasites. To understand the relative importance of host association and biogeography in the evolutionary history of this tapeworm, we analysed mtDNA and reduced-represented genomic SNP data for a total of 139 specimens collected from 18 fish-host genera across a distribution range representing 21 countries. Our results strongly supported the existence of at least 10 evolutionary lineages and estimated the deepest divergence at approximately 4.99–5.05 Mya, which is much younger than the diversification of the fish host genera and orders. Historical biogeography analyses revealed that the ancestor of the parasite diversified following multiple vicariance events and was widespread throughout the Palearctic, Afrotropical, and Nearctic between the late Miocene and early Pliocene. Cyprinoids were inferred as the ancestral hosts for the parasite. Later, from the late Pliocene to Pleistocene, new lineages emerged following a series of biogeographic dispersal and host-switching events. Although only a few of the current Ligula lineages show narrow host-specificity (to a single host genus), almost no host genera, even those that live in sympatry, overlapped between different Ligula lineages. Our analyses uncovered the impact of historical distribution shifts on host switching and the evolution of host specificity without parallel host-parasite co-speciation. Historical biogeography reconstructions also found that the parasite colonized several areas (Afrotropical and Australasian) much earlier than was suggested by only recent faunistic data.