Leo J Borkin’s research while affiliated with Zoological Institute, Russian Academy of Sciences and other places

Animal translocations provide striking examples of the human footprint on biodiversity. Combining continental-wide genomic and DNA-barcoding analyses, we reconstructed the historical biogeography of the Asian black-spined toad (Duttaphrynus melanostictus), a toxic commensal amphibian that currently threatens two biodiversity hotspots through biological invasions (Wallacea and Madagascar). The results emphasize a complex diversification shaped by speciation and mitochondrial introgression that comprises two distinct species. One species (true D. melanostictus) is distributed in the Indian subcontinent and is invasive in Wallacea. The other species, whose nomenclature remains unsettled, diverged from D. melanostictus in the Miocene era (~7 Mya) and diversified across Southeast Asia, from where it was introduced to Madagascar. Remarkably, the Indonesian population of D. melanostictus was recently established from India, which suggests historical, possibly human-assisted dispersal across the Bay of Bengal, reflecting the centuries-old connection between these regions.

The study of genome size variation in cells of vertebrates using the DNA flow cytometry makes it possible to precisely determine polyploid individuals, which is extremely important when studying the processes of reticulate speciation. In addition, in many groups of vertebrates, closely related species often differ in the nuclear DNA content. Therefore, the purpose of our study was to explore the variability of genome size and ploidy in populations of 29 species and subspecies of mountain lizards of the genus Darevskia, as well as their hybrids. As a result of the study, the range of variability in individuals of different ploidy (91% of diploid and 9% of triploid individuals) was established not to overlap. Among diploid species, no correlation was found between the nuclear DNA content and phylogenetic relationships, geographic coordinates, altitude, average annual temperatures and precipitation. Representatives of all studied species complexes (with the exception of D. adjarica) had approximately the same limits of variability. Two species (D. derjugini and D. saxicola) show significant intraspecific variability. Comparisons of the genome size of parthenogenetic and bisexual species generally revealed no noticeable differences between them. Studies of triploid hybrids have shown that their genome size as a whole roughly corresponds to the sum of the average size of the diploid genome of the maternal parthenogenetic species and the haploid genome of the paternal species. The variability of genome sizes within samples of triploid hybrids was on average slightly higher than in most parthenogenetic species, but some lower than in bisexual species. The paper discusses peculiarities of reticulate speciation in this group of animals.

Snake-eyed, or ablepharine skinks, are common residents of the highest mountain ranges on Earth, including the Himalayas, the Tibetan Plateau, Karakoram, Pamir, and Tian Shan, colloquially known as the Roof of the World. Historically, these skinks were alternatively assigned to the genera Scincella, Ablepharus, Asymblepharus, and Hi-malblepharus, but recent revisions proposed to group them in only two genera, namely Protoblepharus (the eastern Himalayan taxa) and Ablepharus (all other taxa). The taxonomy of this group yet remains in a state of flux due to the limited informativeness of available phylogenies (often with little material from the Himalayan region), discrepancies in morphological patterns of variation, and the potentially high yet unconsidered degree of diversity of the group. To shed some light, we assess the mitochondrial diversity and evolution of Himalayan snake-eyed skinks based on >200 individuals sampled across Pakistan, India, Nepal, and China, representing nine out of ten Himalaya currently recognized species. Phylogenetic relationships were inferred from 2998 bp of mitochondrial sequences (12S, 16S, ND2, cyt b). Our analyses reveal a remarkably high cryptic diversity, including 14 to 16 species level lineages within Ablepharus and four species-level lineages within Protoblepharus, which would substantially increase the number of species by at least twofold. This hidden diversity highlights the Himalayas as a center of phylogeographic diversification and endemism, likely shaped by geological and climatic factors associated with orogenesis, which now houses over half of the ablepharine skink species.

The path taken by I. S. Darevsky to the discovery of natural parthenogenesis in rock lizards of the Caucasus (1957, 1958) is tracked, as well as his further developments of the problem of parthenogenesis in lizards in his main papers (1962, 1966, 1967) and monograph (1967). The following issues are considered: geographic and hybrid parthenogenesis, subspecies and species in unisexual lizards, spontaneous males in parthenogenetic species, the essence of I. S. Darevsky’s discovery in the context of different categories of clonal reproduction in animals, the formation of the concept of reticular speciation, and the evolutionary age of clonal forms in various groups of animals.

The problem of the border between Europe and Asia remains open, and quite different opinions have been expressed. Nevertheless, in recent years, they tend to mark it along the foot of the eastern slope of the Ural Range, to the south drawing the border between the Mugodzhary mountains and the Shoshkakol ridge (attributed to the Northern Ustyurt), along the northern Caspian and Ciscaucasia. To the north of this line, there is Europe, and to the south – Asia. The use of different approaches (tectonic, geomorphological, landscape, floristic, faunal, not to mention political and historical-social) to marking the boundary makes it very uncertain. In our work, based on data on the distribution of amphibians and reptiles, we tried to analyze the course of one of the southern sections of the border that falls into the territory of the Aktobe district of Kazakhstan. 32 species of amphibians and reptiles live on the territory of the Aktobe district, but the habitat of 7–8 more needs to be clarified. The heterogeneity of the composition of the fauna can be traced: European and European-Mediterranean species account for about 30%, and Turanian species – for almost 60%. We asked ourselves the question: Can an analysis of their spatial distribution in the light of the problem of interest to us, the border of Europe and Asia? In two European species (Bombina bombina, Coronella austriaca), the eastern boundaries of the ranges are in one way or another confined to the region of the Ural Range. Pelobates vespertinus and Emys orbicularis reach the valley of the Turgay river. All these species do not enter the Caspian lowland. Some Turanian species do not go north of the line Northern Aral Sea – Northern Ustyurt – Northern Caspian and do not go west of the rivers Emba or Ural. However, the toad-headed agamas (Phrynocephalus guttatus, Ph. mystaceus, Ph. helioscopus) and some Eremias species (E. arguta, E. velox) along accumulative and denudation plains penetrate to the north almost to the borders of the Aktobe district with Russia. In the west, they reach valleys of the Volga river. Such data show that in terms of the distribution of animals (here, amphibians and reptiles) it is impossible to draw the border between Europe and Asia as a line. It's more like a crossroads. The biosphere components are flexible. At the "crossroads" of geographical landscapes, in the understanding of S.V. Kalesnik, the "living matter" moving in space, according to V.I. Vernadsky, inevitably has a choice, where "everyone chooses for himself." An example of such a crossroads is the Aktobe district, which is unique in many ways and to a large extent in terms of the population of amphibians and reptiles. Of the actual tasks of studying the herpetofauna of the Aktobe district, one should mention the updating of the species checklist, the analysis of the recent distribution of amphibians and reptiles, and the restoration of the history of their settlement of this unique territory. It is also tempting to elucidate the factors that determine the ecological well-being of European and Turanian species in the region. This will also make it possible to assess the depth of recent changes in the composition of the herpetofauna, and the spatial and quantitative distribution of species against the background of climate transformations and anthropogenic influence.

Hybridogenesis is well-known attributes of water frogs of the genus Pelophylax. The P. esculentus complex consists of two parental species, P. lessonae and P. ridibundus, as well as their hemiclonal (sometimes meroclonal) hybrid, P. esculentus. DNA flow cytometry, genetic and morphometric analyses were used to examine water frog compositions in 27 localities (n = 212) throughout the Dniester River valley in Moldova. Two species were revealed in the studied region (42% individuals were P. esculentus and 58% P. ridibundus). All frogs proved to be diploid. We registered the first species in 74% localities and the second in 78%. Populations, where we found only P. ridibundus occurred in 26% localities and only P. esculentus in 22%, while mixed population systems in 52%. Both species were usually observed in open water bodies and rivers that flow down through agricultural land and urban areas. In populations of P. esculentus the number of males strongly exceeded (90%) the number of females. The half of studied hybrid males was sterile, and most of fertile hybrid males produced sperm with the genome of P. lessonae. Several hybrid males gave the mixture of sperm with genomes of P. lessonae and P. ridibundus (amphispermy) and only one male with the P. ridibundus genome. Both species had the mitochondrial DNA of P. ridibundus. Based on nuclear markers, in P. esculentus and P. ridibundus we revealed the presence of alleles of the closely related Anatolian species P. cf. bedriagae. This might affect the successful reproduction of hybridogenetic P. esculentus. However, comparison of percentage of sterile males and alleles of P. cf. bedriagae among hybrids showed no correlation.

The relict, endemic taxa Allopaa and Chrysopaa are key elements of the Hindu Kush–Himalayan amphibian fauna and potentially share a similar biogeographic evolution, making them important proxies for the reconstruction of the palaeoenvironmental and palaeotopographic history of the Himalaya–Tibet–Orogen. However, little is known about the taxonomy, phylogeography, genetic diversity and distribution of these taxa. We here provide new molecular data on Himalayan spiny frogs and species distribution models (SDMs) for A. hazarensis and C. sternosignata. The results reveal a better resolved phylogeny of these frogs compared to previous trees and strongly support the placement of A. hazarensis in the genus Nanorana. We further identify a so far unknown clade from the western Himalayas in Nanorana, apart from the subgroups Chaparana, Paa and the nominal Nanorana. In A. hazarensis, genetic diversity is relatively low. The results strengthen support for the recently proposed out-of-Tibet-into-the-Himalayan-exile hypothesis and a trans-Tibet dispersal of ancestral spiny frogs during the Palaeogene. Moreover, SDMs provide the first detailed distribution maps of A. hazarensis and C. sternosignata and strong evidence for distinct niche divergence among the two taxa. Our findings contribute to the knowledge about the distribution of these species and provide basic information for guiding future conservation management of them.

The relict, endemic taxa Allopaa and Chrysopaa are key elements of the Hindu Kush-Himalayan amphibian fauna and potentially share a similar biogeographic evolution, making them important proxies for the reconstruction of the palaeoenvironmental and palaeotopographic history of the Himalaya-Tibet-Orogen. However, little is known about the taxonomy, phylogeography, genetic diversity and distribution of these taxa. We here provide new molecular data on Himalayan spiny frogs and species distribution models (SDMs) for A. hazarensis and C. sternosignata. The results reveal a better resolved phylogeny of these frogs compared to previous trees and strongly support the placement of A. hazarensis in the genus Nanorana. We further identify a so far unknown clade from the western Himalayas in Nanorana, apart from the subgroups Chaparana, Paa and the nominal Nanorana. In A. hazarensis, genetic diversity is relatively low. The results strengthen support for the recently proposed out-of-Tibet-into-the-Himalayan-exile hypothesis and a trans-Tibet dispersal of ancestral spiny frogs during the Palaeogene. Moreover, SDMs provide the first detailed distribution maps of A. hazarensis and C. sternosignata and strong evidence for distinct niche divergence among the two taxa. Our findings contribute to the knowledge about the distribution of these species and provide basic information for guiding future conservation management of them.

A known haven of amphibian diversity, South Asia is also a hotspot of taxonomic confusions. Vastly distributed from Saudi Arabia to Myanmar, the dicroglossid genus Euphlyctis (“skittering” or “skipper” frogs) is a representative example. Combining phylogenetic analyses with 16S barcoding and genome size variation of 403 frogs from 136 localities, we examined genetic diversity and distributions across the whole range of Euphlyctis, with a particular focus on taxonomic and nomenclatural issues. We recovered two deeply divergent mitochondrial clades totalling ten lineages that we considered as species, and eight could be attributed valid taxonomic names and junior synonyms. The first clade (subgenus Phrynoderma) is confirmed in South India, Bangladesh and Sri Lanka, and comprises six species: E. karaavali, E. hexadactyla, E. aloysii, E. kerala and two undescribed taxa. Five are endemic to the Western Ghats biodiversity hotspot and four of them form the E. aloysii species complex. The second clade (subgenus Euphlyctis) extends across South Asia and neighbouring regions, and comprises four species: E. ehrenbergii, E. jaladhara, and two widespread lineages erroneously called “E. mudigere” and “E. kalasgramensis” in recent literature, while their oldest valid names appear to be E. cyanophlyctis and E. adolfi, respectively. Additional analyses on this pair of taxa highlighted strong phenotypic resemblance, notable intraspecific phylogeographic structure, and an extensive contact zone along the southern slopes of the Himalaya, with putative signs of genetic introgression. Through an independent investigation of the historical literature, we identified overlooked issues and misconceptions regarding the status of many old and recent taxa, and proposed solutions, such as transferring “E. ghoshi” to the genus Limnonectes. Our study illustrates how range-wide genetic barcoding can clarify taxonomic confusions, and we call to solve remaining issues prior to the description of new taxa