42 research outputs found
Genomic heterogeneity of historical gene flow between two species of newts inferred from transcriptome data
The role of gene flow in species formation is a major unresolved issue in speciation biology. Progress in this area requires information on the longâterm patterns of gene flow between diverging species. Here, we used thousands of singleânucleotide polymorphisms derived from transcriptome resequencing and a method modeling the joint frequency spectrum of these polymorphisms to reconstruct patterns of historical gene flow between two Lissotriton newts: L. vulgaris (Lv) and L. montandoni (Lm). We tested several models of divergence including complete isolation and various scenarios of historical gene flow. The model of secondary contact received the highest support. According to this model, the species split from their common ancestor ca. 5.5 million years (MY) ago, evolved in isolation for ca. 2 MY, and have been exchanging genes for the last 3.5 MY Demographic changes have been inferred in both species, with the current effective population size of ca. 0.7 million in Lv and 0.2 million in Lm. The postdivergence gene flow resulted in twoâdirectional introgression which affected the genomes of both species, but was more pronounced from Lv to Lm. Interestingly, we found evidence for genomic heterogeneity of interspecific gene flow. This study demonstrates the complexity of longâterm gene flow between distinct but incompletely reproductively isolated taxa which divergence was initiated millions of years ago
Post-glacial colonisation of Europe by the wood mouse, Apodemus sylvaticus : evidence of a northern refugium and dispersal with humans
The wood mouse Apodemus sylvaticus is an opportunistic rodent that is found throughout most of
the European mainland. It is present on many islands around the margins of the continent and in
northern Africa. The species has been the subject of previous phylogeographic studies but these
have focussed on the more southerly part of its range. A substantial number of new samples,
many of them from the periphery of the speciesâ range, contribute to an exceptional dataset
comprising 981 mitochondrial cytochrome b sequences. These new data provide sufficient
resolution to transform our understanding of the speciesâ survival through the last glaciation and
its subsequent re-colonisation of the continent. The deepest genetic split we found is in
agreement with previous studies and runs from the Alps to central Ukraine, but we further
distinguish two separate lineages in wood mice to the north and west of this line. It is likely that
this part of Europe was colonised from two refugia, putatively located in the Iberian peninsula and
the Dordogne or Carpathian region. The wood mouse therefore joins the growing number of
species with extant populations that appear to have survived the Last Glacial Maximum in
northern refugia, rather than solely in traditionally recognised refugial locations in the southern
European peninsulas. Furthermore, the existence of a northern refugium for the species was
predicted in a study of mitochondrial variation in a specific parasite of the wood mouse,
demonstrating the potential value of data from parasites to phylogeographic studies. Lastly, the
presence of related haplotypes in widely disparate locations, often on islands or separated by
substantial bodies of water, demonstrates the propensity of the wood mouse for accidental
human-mediated transport
Species History Masks the Effects of Human-Induced Range Loss â Unexpected Genetic Diversity in the Endangered Giant Mayfly Palingenia longicauda
Freshwater biodiversity has declined dramatically in Europe in recent decades. Because of massive habitat pollution and morphological degradation of water bodies, many once widespread species persist in small fractions of their original range. These range contractions are generally believed to be accompanied by loss of intraspecific genetic diversity, due to the reduction of effective population sizes and the extinction of regional genetic lineages. We aimed to assess the loss of genetic diversity and its significance for future potential reintroduction of the long-tailed mayfly Palingenia longicauda (Olivier), which experienced approximately 98% range loss during the past century. Analysis of 936 bp of mitochondrial DNA of 245 extant specimens across the current range revealed a surprisingly large number of haplotypes (87), and a high level of haplotype diversity (). In contrast, historic specimens (6) from the lost range (Rhine catchment) were not differentiated from the extant RĂĄba population (, ), despite considerable geographic distance separating the two rivers. These observations can be explained by an overlap of the current with the historic (Pleistocene) refugia of the species. Most likely, the massive recent range loss mainly affected the range which was occupied by rapid post-glacial dispersal. We conclude that massive range losses do not necessarily coincide with genetic impoverishment and that a species' history must be considered when estimating loss of genetic diversity. The assessment of spatial genetic structures and prior phylogeographic information seems essential to conserve once widespread species
Diversity in the Reproductive Modes of European Daphnia pulicaria Deviates from the Geographical Parthenogenesis
10 pĂĄginas, 5 figuras, 3 tablas.Background: Multiple transitions to obligate parthenogenesis have occurred in the Daphnia pulex complex in North
America. These newly formed asexual lineages are differentially distributed being found predominantly at high latitudes.
This conforms to the rule of geographical parthenogenesis postulating prevalence of asexuals at high latitudes and
altitudes. While the reproductive mode of high-latitude populations is relatively well studied, little is known about the
reproduction mode in high altitudes. This study aimed to assess the reproductive mode of Daphnia pulicaria, a species of
the D. pulex complex, from high altitude lakes in Europe.
Methodology/Principal Findings: Variation at eight microsatellite loci revealed that D. pulicaria from the High Tatra
Mountains (HTM) had low genotype richness and showed excess of heterozygotes and significant deviations from Hardy-
Weinberg expectations, and was thus congruent with reproduction by obligate parthenogenesis. By contrast, populations
from the Pyrenees (Pyr) were generally in Hardy-Weinberg equilibrium and had higher genotypic richness, suggesting that
they are cyclic parthenogens. Four lakes from lowland areas (LLaP) had populations with an uncertain or mixed breeding
mode. All D. pulicaria had mtDNA ND5 haplotypes of the European D. pulicaria lineage. Pyr were distinct from LLaP and
HTM at the ND5 gene. By contrast, HTM shared two haplotypes with LLaP and one with Pyr. Principal Coordinate Analysis of
the microsatellite data revealed clear genetic differentiation into three groups. HTM isolates were intermediate to Pyr and
LLaP, congruent with a hybrid origin.
Conclusion/Significance: Inferred transitions to obligate parthenogenesis have occurred only in HTM, most likely as a result
of hybridizations. In contrast to North American populations, these transitions do not appear to involve meiosis suppressor
genes and have not been accompanied by polyploidy. The absence of obligate parthenogenesis in Pyr, an environment
highly similar to the HTM, may be due to the lack of opportunities for hybridization.Peer reviewe
Contrasting and congruent patterns of genetic structuring in two Microtus vole species using museum specimens
The common vole (Microtus arvalis) and the field vole (Microtus agrestis) are morphologically similar species but are ecological distinctive and differ in the details of their evolutionary history as revealed by mitochondrial DNA (mtDNA). The aim of this study is to describe patterns of genetic variability using microsatellite markers in populations of the common and field vole in Poland using museum specimens, to assess the degree of congruence with mtDNA variation and thereby determine the factors that influence current patterns of gene flow. We genotyped 190 individuals of the common vole at 11 loci and 190 individuals of the field vole at 13 loci. Overall differentiation based on F ST was higher for the common vole than in the field vole. We detected a significant isolation by distance pattern for both species. Bayesian analysis in STRUCTURE identified Eastern and Western geographic groups in Poland based on microsatellites for both species. The location of river barriers is likely to be the main factor in these partitions. The eastern-western subdivision with microsatellites does not coincide with the distribution of mtDNA lineages for either species. Unlike previous studies in the common and field vole elsewhere in Europe, we found no evidence of reproductive isolation between the mtDNA lineages of these species at their contact zones in Poland. This study highlights the different roles of evolutionary history and landscape in shaping contemporary genetic structure in voles in Poland
Gene flow during glacial habitat shifts facilitates character displacement in a Neotropical flycatcher radiation
Relaxed functional constraints on triplicate Îą-globin gene in the bank vole suggest a different evolutionary history from other rodents
Photograph of a young Amish boy driving a horse drawn hay wagon