Cryptic hybridization between the ancient lineages of Natterer's bat (Myotis nattereri).

Studying hybrid zones that form between morphologically cryptic taxa offers valuable insights into the mechanisms of cryptic speciation and the evolution of reproductive barriers. Although hybrid zones have long been the focus of evolutionary studies, the awareness of cryptic hybrid zones increased recently due to rapidly growing evidence of biological diversity lacking obvious phenotypic differentiation. The characterization of cryptic hybrid zones with genome-wide analysis is in its early stages and offers new perspectives for studying population admixture and thus the impact of gene flow. In this study, we investigate the population genomics of the Myotis nattereri complex in one of its secondary contact zones, where a putative hybrid zone is formed between two of its cryptic lineages. By utilizing a whole-genome shotgun sequencing approach, we aim to characterize this cryptic hybrid zone in detail. Demographic analysis suggests that the cryptic lineages diverged during the Pliocene, c. 3.6 million years ago. Despite this ancient separation, the populations in the contact zone exhibit mitochondrial introgression and a considerable amount of mixing in nuclear genomes. The genomic structure of the populations corresponds to geographic locations and the genomic admixture changes along a geographic gradient. These findings suggest that there is no effective hybridization barrier between both lineages, nevertheless, their population structure is shaped by dispersal barriers. Our findings highlight how such deeply diverged cryptic lineages can still readily hybridize in secondary contact.

Patterns of mtDNA introgression suggest population replacement in Palaearctic whiskered bat species.

Secondary contacts can play a major role in the evolutionary histories of species. Various taxa diverge in allopatry and later on come into secondary contact during range expansions. When they meet, their interactions and the extent of gene flow depend on the level of their ecological differentiation and the strength of their reproductive isolation. In this study, we present the multilocus phylogeography of two cryptic whiskered bat species, Myotis mystacinus and M. davidii, with a particular focus on their putative sympatric zone. Our findings suggest that M. mystacinus and M. davidii evolved in allopatry and came into secondary contact during range expansions. Individuals in the area of secondary contact, in Anatolia and the Balkans, have discordant population assignments based on the mitochondrial and the nuclear datasets. These observed patterns suggest that the local M. mystacinus populations hybridized with expanding M. davidii populations, which resulted in mitochondrial introgression from the former. In the introgression area, M. mystacinus individuals with concordant nuclear and mitochondrial genotypes were identified in relatively few locations, suggesting that the indigenous populations might have been largely replaced by invading M. davidii. Changing environmental conditions coupled with ecological competition is the likely reason for this replacement. Our study presents one possible example of a historical population replacement that was captured in phylogeographic patterns.

The complete mitochondrial genome of the lesser sac-winged bat Saccopteryx leptura (Chiroptera: Emballonuridae) from Costa Rica.

Here we present the first complete mitochondrial genome of the lesser sac-winged bat Saccopteryx leptura (Chiroptera: Emballonuridae) from Costa Rica, assembled from next-generation sequencing data. The mitogenome of Saccopteryx leptura measures 16,577 bp in length, and contains 13 protein-coding genes, 2 ribosomal RNA genes and 22 transfer RNA genes. A slight A + T bias was observed in the mitogenome of Saccopteryx leptura with an overall base composition of 31.5% A, 28.3% T, 25.8% C, and 14.2% G, and a GC content of 40.1%. The gene arrangement was identical to that of previously described bat mitogenomes.

Cryptic diversity of the bent-wing bat, Miniopterus schreibersii (Chiroptera: Vespertilionidae), in Asia Minor.

BACKGROUND: Two or more species are cryptic, if they are morphologically similar, biologically distinct, and misclassified as a single species. Cryptic species complexes were recently discovered within many bat species and we suspect that the bent-wing bat, Miniopterus schreibersii, found in Europe, northern Africa, and Asia Minor, could also form such a complex. Populations of M. schreibersii decline in most of the European countries and the species is currently listed as Near Threatened in the IUCN Red List. Finding that M. schreibersii is not a single species, but a species complex, would have a considerable impact on its conservation strategies, as the abundance of each component taxon would be much smaller than the one estimated for the nominal species. RESULTS: Miniopterus schreibersii in Asia Minor consists of two genetically diverged lineages, which are reciprocally monophyletic on three mitochondrial DNA markers, have a diagnostic set of multilocus allele frequencies, and show a marked difference in their population structures. The lineages differ slightly in their size, wing shape, and echolocation call parameters. Although these differences are sufficient to discriminate between the lineages, they are not fully diagnostic in reference to individuals. We suggest that the lineages endured the major Northern Hemisphere glaciations in different glacial refugia and colonized Asia Minor after the last glacial maximum. The lineages are allopatric, which is neither delineated by the presence of geographical barriers nor associated with the specific climatic conditions, and which we link to competitive exclusion. CONCLUSIONS: The distinctions between the lineages comply with most of the criteria required for species delineation imposed by various species concepts. Accordingly, we conclude that M. schreibersii in Asia Minor is represented by two cryptic species. Our results imply that the distributional range of the nominal species is almost exclusively limited to Europe and the coastal zones of Asia Minor. As populations of M. schreibersii seem to be much smaller than currently assumed, conservation strategies regarding this taxon need to be revised. The exact distributional range and the vulnerability of the suggested sister species to M. schreibersii is yet to be assessed.

Regionally and climatically restricted patterns of distribution of genetic diversity in a migratory bat species, Miniopterus schreibersii (Chiroptera: Vespertilionidae).

BACKGROUND: Various mechanisms such as geographic barriers and glacial episodes have been proposed as determinants of intra-specific and inter-specific differentiation of populations, and the distribution of their genetic diversity. More recently, habitat and climate differences, and corresponding adaptations have been shown to be forces influencing the phylogeographic evolution of some vertebrates. In this study, we examined the contribution of these various factors on the genetic differentiation of the bent-winged bat, Miniopterus schreibersii, in southeastern Europe and Anatolia. RESULTS AND CONCLUSION: Our results showed differentiation in mitochondrial DNA coupled with weaker nuclear differentiation. We found evidence for restriction of lineages to geographical areas for hundreds of generations. The results showed that the most likely ancestral haplotype was restricted to the same geographic area (the Balkans) for at least 6,000 years. We were able to delineate the migration routes during the population expansion process, which followed the coasts and the inland for different nested mitochondrial clades. Hence, we were able to describe a scenario showing how multiple biotic and abiotic events including glacial periods, climate and historical dispersal patterns complemented each other in causing regional and local differentiation within a species.