Dispersal History Research Articles

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.

Accommodating sampling location uncertainty in continuous phylogeography.

Phylogeographic inference of the dispersal history of viral lineages offers key opportunities to tackle epidemiological questions about the spread of fast-evolving pathogens across human, animal and plant populations. In continuous space, i.e. when locations are specified by longitude and latitude, these reconstructions are however often limited by the availability or accessibility of precise sampling locations required for such spatially explicit analyses. We here review the different approaches that can be considered when genomic sequences are associated with a geographic area of sampling instead of precise coordinates. In particular, we describe and compare the approaches to define homogeneous and heterogeneous prior ranges of sampling coordinates.

Early-phase colonisation by introduced sculptured resin bee (Hymenoptera, Megachilidae, Megachile sculpturalis) revealed by local floral resource variability

There is a growing interest to document and better understand patterns and processes involved in non-native bee introductions and subsequent colonisation of new areas worldwide. We studied the spread of the East Asian bee Megachile sculpturalis in Serbia and south-eastern Europe; the bee was earlier established in the USA (since 1994) and western Europe (since 2008). Its establishment in Serbia remained dubious throughout most of 2017–2019, following its first detection. We hereby report on its establishment and spreading, which were corroborated in 2019 under specific circumstances. Owing to an exceptionally poor blooming of Styphnolobium japonicum in 2019, we recorded a high activity density of M. sculpturalis concentrated on a scarce key food resource. We present a novel quantitative approach for an improved early detection of M. sculpturalis, based on the interplay between the bee local occurrence pattern and dynamics of key food-plant(s) availability. This approach seems particularly effective during the early-phase colonisation, at initially low population density of introduced bees. We address the importance of integration of the genuine plant usage patterns with context-specific bee assessment options in establishing effective monitoring. The improved understanding of M. sculpturalis local dynamics triggered the questions about possible origin(s) and modes of its dispersal east of the Alps. To explore the possible scenarios of M. sculpturalis introduction(s), we extended the study to a wider spatio-temporal context – the region of SE Europe (2015–2019). The two complementary study approaches (at local and regional scale) provided more comprehensive evidence of bee dispersal history and the detection patterns in varied recording contexts. Based on this two-scale approach, we suggest that a diffusive mode of M. sculpturalis introduction into Serbia now seems to be a more plausible scenario (than a long-distance jump). We argue that the integration of outcomes from the contrasting approaches (a systematic surveillance, based on plant resources and a broad-scale opportunistic recording) could be of great methodological relevance for the development of future monitoring protocols.

Palaeogenomic analysis of black rat (Rattus rattus) reveals multiple European introductions associated with human economic history

The distribution of the black rat (Rattus rattus) has been heavily influenced by its association with humans. The dispersal history of this non-native commensal rodent across Europe, however, remains poorly understood, and different introductions may have occurred during the Roman and medieval periods. Here, in order to reconstruct the population history of European black rats, we first generate a de novo genome assembly of the black rat. We then sequence 67 ancient and three modern black rat mitogenomes, and 36 ancient and three modern nuclear genomes from archaeological sites spanning the 1st-17th centuries CE in Europe and North Africa. Analyses of our newly reported sequences, together with published mitochondrial DNA sequences, confirm that black rats were introduced into the Mediterranean and Europe from Southwest Asia. Genomic analyses of the ancient rats reveal a population turnover in temperate Europe between the 6th and 10th centuries CE, coincident with an archaeologically attested decline in the black rat population. The near disappearance and re-emergence of black rats in Europe may have been the result of the breakdown of the Roman Empire, the First Plague Pandemic, and/or post-Roman climatic cooling.

Human‐mediated eco‐evolutionary processes of the herbivorous insect Hyalopterus arundiniformis during the Holocene

AbstractAimPleistocene climatic fluctuations have been identified as a dominant factor in evolutionary and ecological processes underlying contemporary species distribution. In contrast, anthropogenic activity during the Holocene has been largely neglected in phylogeographic inference. Here, by integrating archaeological evidence, phylogeographic analyses and a climatic niche‐based approach, the role of Holocene human activity in determining the evolutionary trajectory of insect pests is investigated using Hyalopterus arundiniformis (HAR) as a model.LocationEurasia.MethodsWe compiled archaeological records and historical data for the host plant (i.e. peach) of HAR. Phylogeographic structure, genetic diversity and gene flow were estimated. Historical demographic dynamics were explored using coalescent‐based analyses. The origin and dispersal history were assessed using an approximate Bayesian computation (ABC) approach. The changes in climatic niche breadth during geographic expansion were evaluated via niche comparison analyses.ResultsOur results revealed that HAR originated in Southwest China and dispersed to Southeast and Northwest China, and it was then introduced to western Eurasia from Northwest China. The climatic niche shifted significantly with range expansions, and niche expansion explained the largest proportion of niche dynamics. Population size expansion occurred in the Holocene and coincided with the domestication and trans‐Eurasian trade of peach.Main conclusionsThe geographic range, effective population size and climatic niche breadth of HAR expanded following the human‐mediated dispersal of its host plant during the Holocene. Our results highlight that the expansion of Neolithic agriculture and trans‐Eurasian crop exchange along ancient communication routes may have played an important role in shaping the distribution and demographic dynamics of herbivorous insects. This study also provides essential information for pest management and biological invasions.

Profiling, monitoring and conserving caterpillar fungus in the Himalayan region using anchored hybrid enrichment markers.

The collection of caterpillar fungus accounts for 50–70% of the household income of thousands of Himalayan communities and has an estimated market value of $5–11 billion across Asia. However, Himalayan collectors are at multiple economic disadvantages compared with collectors on the Tibetan Plateau because their product is not legally recognized. Using a customized hybrid-enrichment probe set and market-grade caterpillar fungus (with samples up to 30 years old) from 94 production zones across Asia, we uncovered clear geography-based signatures of historical dispersal and significant isolation-by-distance among caterpillar fungus hosts. This high-throughput approach can readily distinguish samples from major production zones with definitive geographical resolution, especially for samples from the Himalayan region that form monophyletic clades in our analysis. Based on these results, we propose a two-step procedure to help local communities authenticate their produce and improve this multi-national trade-route without creating opportunities for illegal exports and other forms of economic exploitation. We argue that policymakers and conservation practitioners must encourage the fair trade of caterpillar fungus in addition to sustainable harvesting to support a trans-boundary conservation effort that is much needed for this natural commodity in the Himalayan region.

Population Genetic Structure and Diversity of Metaphire remanens (Oligochaeta: Megascolecidae) Based on Mitochondrial DNA Analysis, with a Note on a New Species of Metaphire remanens sp. nov.

Metaphire remanens sp. nov. is widely distributed throughout Hunan Province, China. We sequenced the mitochondrial DNA to investigate its population genetic structure and genetic diversity, including cytochrome c oxidase subunit I, cytochrome c oxidase subunit II, 12S ribosomal (r)RNA, 16S rRNA, and nicotinamide adenine dinucleotide dehydrogenase subunit 1, derived from 39 individuals from seven geographic locations in Hunan Province. The genetic diversity indices showed that populations of M. remanens have a strong genetic structure and obvious dispersal histories. M. remanens did not experience population expansion, except in Xiangtan City. This may be because of its evolution toward parthenogenesis. The divergence time estimates indicated that M. remanens originated at 19.2055 Ma and then generated two main lineages at 1.7334 Ma (Quaternary glaciation). These results indicate that glaciation, geographic isolation, and dispersal ability are significant factors that influence the differentiation and dispersal of M. remanens. In this study, we describe Metaphire remanens sp. nov. in morphology.

Phylogenetic phytogeography of selected groups of seagrasses (Monocotylendoneae - Alismatales) based on analysing of genes 5.8S rRNA and RuBisCo large subunit

Seagrasses are representatives of the families Cymodoceaceae, Posidoniaceae, Zosteraceae, Hydrocharitaceae (Monocotylendoneae - Alismatales), adapted to growing in seawaters and all their important life circle events are taking place under the water including pollination and distribution of diasporas. Seagrasses are widespread in the littoral areas of the World Ocean, except for Antarctica, and play an important ecosystem role. Due to the insufficiently studied history of dispersal and formation of modern seagrasses habitats, we carried out a phylogenetic analysis of representatives of the families Cymodoceaceae (Amphibolis, Halodule, Syringodium, Cymodocea, and Thalassodendron), Posidoniaceae (Posidonia), Zosteraceae (Zostera, and Phyllospadix), and Hydrocharitaceae (Enhalus, Halophila, and Thalassia). The cladograms constructed based on molecular data analysis of the 5.8S ribosomal RNA and ribulose–1,5–bisphosphate carboxylase/oxygenase large subunit genes are used as the basis for reconstructing the history of dispersal of the studied taxa. It is found that the main stages of dispersal of selected groups of seagrasses took place in the Late Cretaceous period. The main track of historical distribution is largely predetermined by the modern ranges of almost all genera of seagrasses, stretches from the southwestern waters of eastern Gondwana to the northwestern waters of the Eurasian part of Laurasia. The main route of movement of diasporas and seagrasses populations was the Tethys water area, which was modified in the Late Mesozoic and early Cenozoic. It was revealed that the main method of dispersal of seagrasses was long-distance dispersal, which is confirmed by both molecular genetic data and very fast (on a geological time scale) processes of penetration into new water areas, and analysis of the features of dissemination of modern representatives. An alternative vicar scenario was proposed only for the reconstruction of the formation of the Posidonia range.

A New Way to Trace SARS-CoV-2 Variants Through Weighted Network Analysis of Frequency Trajectories of Mutations.

Early detection of SARS-CoV-2 variants enables timely tracking of clinically important strains in order to inform the public health response. Current subtype-based variant surveillance depending on prior subtype assignment according to lag features and their continuous risk assessment may delay this process. We proposed a weighted network framework to model the frequency trajectories of mutations (FTMs) for SARS-CoV-2 variant tracing, without requiring prior subtype assignment. This framework modularizes the FTMs and conglomerates synchronous FTMs together to represent the variants. It also generates module clusters to unveil the epidemic stages and their contemporaneous variants. Eventually, the module-based variants are assessed by phylogenetic tree through sub-sampling to facilitate communication and control of the epidemic. This process was benchmarked using worldwide GISAID data, which not only demonstrated all the methodology features but also showed the module-based variant identification had highly specific and sensitive mapping with the global phylogenetic tree. When applying this process to regional data like India and South Africa for SARS-CoV-2 variant surveillance, the approach clearly elucidated the national dispersal history of the viral variants and their co-circulation pattern, and provided much earlier warning of Beta (B.1.351), Delta (B.1.617.2), and Omicron (B.1.1.529). In summary, our work showed that the weighted network modeling of FTMs enables us to rapidly and easily track down SARS-CoV-2 variants overcoming prior viral subtyping with lag features, accelerating the understanding and surveillance of COVID-19.

Dispersal and life history of brown widow spiders in dated invasive populations on two continents

Theory and empirical work suggest that behaviours such as dispersal and exploration are predictors of invasive success, and that behaviours may shift predictably after invasive populations have established and spread. However, there are limited data on temporal patterns in the distribution of behavioural traits linked to the timeline of establishment of invasive species. We examined dispersal and exploration, along with life history traits that may be linked to behaviour, across multiple invasive populations of the brown widow spider, Latrodectus geometricus. This global invader has established populations across the United States and Israel. Using this temporal and spatial variation, we tested predictions about changes in suites of traits over establishment time. We compared trait distributions of four U.S. populations of L. geometricus to patterns in four populations in Israel. We predicted that selective filters during the invasion process would result in more dispersive, more exploratory spiders that are larger and more fecund in recently established populations, but, if trade-offs occur, dispersal would be favoured at the expense of fecundity and size in recent populations. We found more frequent and faster dispersal in more recently established populations in Israel, but not the United States. Spiders in more recently established populations in Israel were larger than those in older populations, but there were no consistent patterns across U.S. populations. However, there was evidence in both the U.S. and Israel for differing trade-offs among fecundity, dispersal and size. In more recently established populations, spiders were more variable in resource allocation to eggsacs. The results suggest that in some populations, trade-offs underlying dispersal, fecundity and body size are shaped by the time interval, and thus the number of generations, since establishment, with implications for the role of evolutionary processes in invasion success.

Genomic Screening to Identify Food Trees Potentially Dispersed by Precolonial Indigenous Peoples.

Over millennia, Indigenous peoples have dispersed the propagules of non-crop plants through trade, seasonal migration or attending ceremonies; and potentially increased the geographic range or abundance of many food species around the world. Genomic data can be used to reconstruct these histories. However, it can be difficult to disentangle anthropogenic from non-anthropogenic dispersal in long-lived non-crop species. We developed a genomic workflow that can be used to screen out species that show patterns consistent with faunal dispersal or long-term isolation, and identify species that carry dispersal signals of putative human influence. We used genotyping-by-sequencing (DArTseq) and whole-plastid sequencing (SKIMseq) to identify nuclear and chloroplast Single Nucleotide Polymorphisms in east Australian rainforest trees (4 families, 7 genera, 15 species) with large (>30 mm) or small (<30 mm) edible fruit, either with or without a known history of use by Indigenous peoples. We employed standard population genetic analyses to test for four signals of dispersal using a limited and opportunistically acquired sample scheme. We expected different patterns for species that fall into one of three broadly described dispersal histories: (1) ongoing faunal dispersal, (2) post-megafauna isolation and (3) post-megafauna isolation followed by dispersal of putative human influence. We identified five large-fruited species that displayed strong population structure combined with signals of dispersal. We propose coalescent methods to investigate whether these genomic signals can be attributed to post-megafauna isolation and dispersal by Indigenous peoples.

A phylogenetic analysis of dispersal norms, descent and subsistence in Sino-Tibetans

Sex-biased dispersal has long been of interest to anthropologists and biologists, as it can structure populations and determine patterns of kinship, relatedness and cooperation. In most contemporary human societies, females usually disperse at marriage. In a minority of human societies, male dispersal, bisexual philopatry, or both sexes dispersing is practiced. Previous studies suggest that emergence of either agriculture, cattle pastoralism, or patriliny is associated with female-biased dispersal in certain language families. The ancestral patterns of sex-specific dispersal and its ecological correlates in Sino-Tibetans remain uncertain. Here we use comparative phylogenetic methods to infer the evolutionary history of sex-specific dispersal in Sino-Tibetan groups, and tested for coevolution between subsistence (agriculture and cattle-keeping), descent and sex-specific dispersal. We use a variety of ethnographic and historical sources to identify dispersal strategies across Sino-Tibetan phylogenetic trees ( n = 97). We found that 1) earliest Sino-Tibetan groups were likely patrilocal; 2) agriculture likely co-evolved with only female dispersal patterns, but the result is sensitive to alternative coding strategy; 3) there is no evidence that domestic cattle co-evolved with dispersal patterns of either gender; and 4) kinship descent likely co-evolved with female dispersal, but not with male dispersal. Moreover, change from state of “patrilineal” to “non-patrilineal” triggered change in female dispersal patterns, from “female non-stay” to “female stay”. Our results suggest that change in descent drove change in female-specific dispersal pattern in Sino-Tibetans. Our findings illustrated how subsistence or descent can play different roles in shaping sex-biased dispersal patterns.

Reconstructing the Environmental Context of Human Origins in Eastern Africa Through Scientific Drilling

Paleoanthropologists have long speculated about the role of environmental change in shaping human evolution in Africa. In recent years, drill cores of late Neogene lacustrine sedimentary rocks have yielded valuable high-resolution records of climatic and ecosystem change. Eastern African Rift sediments (primarily lake beds) provide an extraordinary range of data in close proximity to important fossil hominin and archaeological sites, allowing critical study of hypotheses that connect environmental history and hominin evolution. We review recent drill-core studies spanning the Plio–Pleistocene boundary (an interval of hominin diversification, including the earliest members of our genus Homo and the oldest stone tools), and the Mid–Upper Pleistocene (spanning the origin of Homo sapiens in Africa and our early technological and dispersal history). Proposed drilling of Africa's oldest lakes promises to extend such records back to the late Miocene. ▪ High-resolution paleoenvironmental records are critical for understanding external drivers of human evolution. ▪ African lake basin drill cores play a critical role in enhancing hominin paleoenvironmental records given their continuity and proximity to key paleoanthropological sites. ▪ The oldest African lakes have the potential to reveal a comprehensive paleoenvironmental context for the entire late Neogene history of hominin evolution.

Paleozoic–Mesozoic dispersal of Gondwana: Insights from detrital zircon geochronology of Lesser Himalaya strata, eastern Nepal

Abstract Detrital zircon geochronology has rapidly evolved into a powerful tool for reconstructing the assembly and dispersal processes of supercontinents. Currently, the dispersal history of Gondwanaland remains highly controversial. Here we focus on detrital zircon geochronology of the Gondwana (Carboniferous–Permian Kokaha Diamictite and Jurassic–Cretaceous Sapt Koshi Formation) and post-Gondwana (Miocene Tamrang Formation) sequences of the Lesser Himalaya in eastern Nepal. Detrital zircon U-Pb dating results show that the Carboniferous–Permian sequence peaks at 544 Ma, 890 Ma, 1178 Ma, and 1752 Ma. Likewise, the Jurassic–Cretaceous sequence peaks at 531 Ma, 947 Ma, 1176 Ma and 1806 Ma along with a much younger peak at 123 Ma. Similarly, the Miocene sequence peaks at 526 Ma, 987 Ma, and 1740 Ma. Comparing these newly obtained ages with those of surrounding regions, we confirm that during the Carboniferous–Permian, the Indian continent was still connected to Gondwana. The U-Pb age distribution of the Kokaha Diamictite coincides with that of the Tethys Himalaya, which further suggests the possibility that this unit either shared the same provenance with or was recycled from the Tethys Himalaya. During the early Mesozoic, the Indian plate rifted from Gondwana and drifted northward, as evidenced by Triassic–Jurassic, rift-related magmatism along the Indian continental margin. Remarkably, there were significant inputs from the Rajmahal Basalt during deposition of the Jurassic–Cretaceous sequence. Besides, the Miocene sequence records a large number of zircons that closely resemble those of the Greater Himalaya, which implies that the Greater Himalaya may have already been uplifted and eroded by then.

Origin and Demographic History of Philippine Pigs Inferred from Mitochondrial DNA.

The Philippines is a mega-diverse country that lies at the crossroads of past human migrations in the Asia-Pacific region and is believed to have never been connected to the Asian continent, even during the major sea-level subsidence of the Quaternary. As a result, the history of pig dispersal in the Philippines remains controversial, due to limited molecular studies and absence of archaeological evidence of pig domestication. This study provides the first comprehensive analysis of 184 complete mitochondrial DNA D-loop region from Philippine pigs to elucidate their early dispersal history by performing a phylogenetic comparison with wild boars and domestic pigs worldwide. The results showed a demographic signal of the ancestry of Philippine pigs that had a close genetic relationship with those from the mainland Southeast Asia and Northeast Asia, suggesting gene flow that may have resulted from human migration and trade. Here we have suggested two possible dispersal routes. One parallels the Neolithic expansion in Island Southeast Asia and Oceania via Northeast Asia, the other from the mainland Southeast Asia, into Palawan and Sulu Archipelago as early as prehistoric times via the Sundaic Region. Despite geographic barriers to migration, numerous genetic lineages have persisted across the Philippine islands, even justifying the recognition of a Philippine Lanyu subclade. The prehistoric population history suggests a demographic expansion that coincided with the interglacial periods of the Pleistocene and may have spread from the southern regions into the eastern and central regions of the Philippines. The intriguing signal of discrepancy discovered between the ancestral pattern and distribution range of the numerous endemic Philippine wild pigs opens a challenging new approach to illuminate complexity among these animals. Our study has contributed significantly towards completing the sparse molecular studies on Philippine pigs, an essential for creating win-win conservation measures.

An evaluation of parapatric distributions among ecologically similar rattlesnakes (Viperidae:Crotalus) in North American warm deserts

AbstractParapatric distributions between ecologically similar species have the potential to reveal the effects of limiting similarity in large-scale patterns of species coexistence. We present a qualitative model that predicts three different types of parapatric boundaries between competing species pairs: gap parapatry, abrupt parapatry and narrow sympatry. Our model integrates both niche-based and neutral theory perspectives of coexistence in the context of climatic tolerances, species equivalence, contingencies of dispersal history, priority effects and a heterogeneous patchwork of optimal and suboptimal habitat. Using species distribution models, tests of niche overlap and phylogeographical data, we evaluated assumptions and conditions of this model for four species of mostly allopatric, rock-dwelling rattlesnakes (Viperidae: Crotalus) inhabiting arid mountain ranges of the Mohave–Sonoran desert system of western North America. Our model was adequate for predicting the different types of range boundaries observed across this guild of ecologically similar species. Where species distributions were separated by a steep climatic gradient without evidence of recent dispersal, we observed gap parapatry; where historical dispersal was asymmetric, we observed abrupt parapatry; and finally, where historical dispersal was symmetric, we observed narrow sympatry.

Insights Into the Environmental Impact on Genetic Structure and Larval Dispersal of Crown-of-Thorns Starfish in the South China Sea

The coral-eating crown-of-thorns starfish (COTS; Acanthaster spp.) play a major role in coral reef degradation in the Indo-Pacific region. However, the impacts of environmental factors on the phylogenetic and genetic characteristics of COTS in the northern Indo-Pacific convergence region remains unclear. We used mitochondrial DNA (mtDNA) and microsatellite markers to analyze the phylogenetic relationship, demographic history, genetic diversity and genetic structure of COTS in the South China Sea (SCS) and explored the impact of environmental factors on historical population expansion, genetic differentiation and larval dispersal. There was a clear signature of a population expansion in the SCS using the mtDNA marker. According to microsatellite loci analysis, COTS have high genetic diversity in the SCS. STRUCTURE analysis indicated that COTS in the Pacific Ocean can be divided into four subgroups: the SCS, Western Pacific, Pacific equatorial current affected zone, and Pacific insular atolls populations in the Pacific Ocean. Fst-statistical analysis revealed positive correlations between the Fst values and geographic isolation for all sampling sites. Additionally, there were no clear associations between the Fst values and chlorophyll a concentrations among coral reefs in the SCS; however, there were significant positive associations between the Fst values and particulate organic carbon (POC) concentrations within small geographic distances. These results suggest that COTS underwent historical population expansion after the Last Glacial Maximum, possibly followed by coral population expansion. The genetic structure of COTS populations may have been shaped by distinct nutrient concentrations, particularly those of POC, over small geographic distances. Moreover, ocean currents provide a potential dispersal mechanism for COTS larvae in the SCS. This study demonstrates that environmental and oceanographic factors play important roles in shaping the genetic characteristics and larval dispersal of COTS populations in the northern Indo-Pacific convergence region.

Diatom biogeography in freshwaters – new insights from between-region comparisons and the role of unmeasured environmental factors

Diatom biogeography has attracted increased attention especially over the past two decades. However, due to covariance between space and environment, diatom biogeographical studies suffer from the fundamental problem of reliably evaluating the relative roles of dispersal processes versus local environment in shaping diatom distributions. Using between-region comparisons, we investigate whether diatom community differences stem partly from dispersal effects or are purely driven by the local environment. The data used comprise diatom presence–absence records and associated environmental-variable data from streams in Iceland and in northern Fennoscandia (Finland and Norway), and from ponds and lakes in Italy and northern Fennoscandia. We found that between-region differences were larger for diatom community composition than for local environmental variables, perhaps suggesting that biogeographical factors such as dispersal limitation or dispersal history influenced diatom communities causing their spatial segregation. We further discuss methods for disentangling the roles of spatial and environmental effects in shaping diatom communities. Finally, we highlight the possible role of unmeasured environmental factors in diatom biogeographical research.

Insights into the Migration Routes and Historical Dispersion of Species Surviving the Messinian Crisis: The Case of Patella ulyssiponensis and Epizoic Rhodolith Lithophyllum hibernicum

The genus Patella (Patellogastropoda, Mollusca) is represented by a group of species exclusive to the Northeast Atlantic Ocean (including Macaronesian archipelagos) and Mediterranean Sea. The species Patella ulyssiponensis and Patella aspera are common in European waters, with the first inhabiting continental coast, and the second endemic to Macaronesian archipelagos. However, the acceptance of these two lineages as separate species is still highly debated. The red coralline species algae Lithophyllum hibernicum, distributed from Northeast Atlantic to the Mediterranean, is usually found as epilithic crusts or unattached forms (named rhodolith beds), although it also forms epizoic crusts on other organisms, e.g., shell surfaces. In order to study the historic dispersal and migration routes of the Patella ulyssiponensis-aspera complex, taxonomic, genetic and biogeographic approaches were employed based on haplotype network analyses and estimations for the most common recent ancestor (TMRCA), using Cytochrome Oxydase I. A synonymy for these two species is proposed, with the presence of a shared haplotype between the continental (P. ulyssiponensis) and insular (P. aspera) lineages, and with basis of morphological and nomenclatural data. We propose an evolutionary scenario for its dispersal based on a high haplotype diversity for the Mediterranean regions, indicating its possible survival during the Messinian Salinity Crisis (6–5.3 Mya), followed by a colonization of the Proto-Macaronesian archipelagos. The epizoic association of L. hibernicum on P. ulyssiponensis shell adult surface is recorded in this study, likewise the promotion of settlement conditions provided by these coralline algae to P. ulyssiponensis larvae, may explain the reach of P. ulyssiponensis distribution through rhodolith transportation.

New insights into the dispersion history and adaptive evolution of taxon Aegilops tauschii in China

Aegilops tauschii, the wild progenitor of wheat D-genome and a valuable germplasm for wheat improvement, has a wide natural distribution from eastern Turkey to China. However, the phylogenetic relationship and dispersion history of Ae. tauschii in China has not been scientifically clarified. In this study, we genotyped 208 accessions (with 104 in China) using ddRAD sequencing and 55K SNP array, and classified the population into six sublineages. Three possible spreading routes or events were identified, resulting in specific distribution patterns, with four sublineages found in Xinjiang, one in Qinghai, two in Shaanxi and one in Henan. We also established the correlation of SNP-based, karyotype-based and spike-morphology-based techniques to demonstrate the internal classification of Ae. tauschii, and developed consensus dataset with 1245 putative accessions by merging data previously published. Our analysis suggested that eight inter-lineage accessions could be assigned to the putative Lineage 3 and these accessions would help to conserve the genetic diversity of the species. By developing the consensus phylogenetic relationships of Ae. tauschii, our work validated the hypothesis on the dispersal history of Ae. tauschii in China, and contributed to the efficient and comprehensive germplasm-mining of the species.