Vlastimil Šlechta’s research while affiliated with Czech Academy of Sciences, Institute of Animal Physiology and Genetics and other places

Eurasia has undergone substantial tectonic, geological, and climatic changes throughout the Cenozoic, primarily associated with tectonic plate collisions and a global cooling trend. The evolution of present-day biodiversity unfolded in this dynamic environment, characterised by intricate interactions of abiotic factors. However, comprehensive, large-scale reconstructions illustrating the extent of these influences are lacking. We reconstructed the evolutionary history of the freshwater fish family Nemacheilidae across Eurasia and spanning most of the Cenozoic on the base of 471 specimens representing 279 species and 37 genera plus outgroup samples. Molecular phylogeny using six genes uncovered six major clades within the family, along with numerous unresolved taxonomic issues. Dating of cladogenetic events and ancestral range estimation traced the origin of Nemacheilidae to Indochina around 48 mya. Subsequently, one branch of Nemacheilidae colonised eastern, central, and northern Asia, as well as Europe, while another branch expanded into the Burmese region, the Indian subcontinent, the Near East, and northeast Africa. These expansions were facilitated by tectonic connections, favourable climatic conditions, and orogenic processes. Conversely, aridification emerged as the primary cause of extinction events. Our study marks the first comprehensive reconstruction of the evolution of Eurasian freshwater biodiversity on a continental scale and across deep geological time.

Eurasia has undergone substantial tectonic, geological, and climatic changes throughout the Cenozoic era, primarily associated with tectonic plate collisions and a global cooling trend. The evolution of present-day biodiversity unfolded in this dynamic environment, characterised by intricate interactions of abiotic factors. However, comprehensive, large-scale reconstructions illustrating the extent of these influences are lacking. We reconstructed the evolutionary history of the freshwater fish family Nemacheilidae across Eurasia and spanning most of the Cenozoic era on the base of 471 specimens representing 279 species and 37 genera. Molecular phylogeny using 6 genes uncovered six major clades within the family, along with numerous unresolved taxonomic issues. Dating of cladogenetic events and ancestral range estimation traced the origin of Nemacheilidae to Indochina around 48 million years ago. Subsequently, one branch of Nemacheilidae colonised eastern, central, and northern Asia, as well as Europe, while another branch expanded into the Burmese region, the Indian subcontinent, the Near East, and northeast Africa. These expansions were facilitated by tectonic connections, favourable climatic conditions, and orogenic processes. Conversely, aridification emerged as the primary cause of extinction events. Our study marks the first comprehensive reconstruction of the evolution of Eurasian freshwater biodiversity on a continental scale and across deep geological time.

Eurasia has undergone substantial tectonic, geological, and climatic changes throughout the Cenozoic era, primarily associated with tectonic plate collisions and a global cooling trend. The evolution of present-day biodiversity unfolded in this dynamic environment, characterised by intricate interactions of abiotic factors. However, comprehensive, large-scale reconstructions illustrating the extent of these influences are lacking. We reconstructed the evolutionary history of the freshwater fish family Nemacheilidae across Eurasia and spanning most of the Cenozoic era. Molecular phylogeny uncovered six major clades within the family, along with numerous unresolved taxonomic issues. Dating of cladogenetic events and ancestral range estimation traced the origin of Nemacheilidae to Indochina around 48 million years ago. Subsequently, one branch of Nemacheilidae colonised eastern, central, and northern Asia, as well as Europe, while another branch expanded into the Burmese region, the Indian subcontinent, the Near East, and northeast Africa. These expansions were facilitated by tectonic connections, favourable climatic conditions, and orogenic processes. Conversely, aridification emerged as the primary cause of extinction events. Our study marks the first comprehensive reconstruction of the evolution of Eurasian freshwater biodiversity on a continental scale and across deep geological time.

Eurasia has undergone substantial tectonic, geological, and climatic changes throughout the Cenozoic era, primarily associated with tectonic plate collisions and a global cooling trend. The evolution of present-day biodiversity unfolded in this dynamic environment, characterised by intricate interactions of abiotic factors. However, comprehensive, large-scale reconstructions illustrating the extent of these influences are lacking. We reconstructed the evolutionary history of the freshwater fish family Nemacheilidae across Eurasia and spanning most of the Cenozoic era. Molecular phylogeny uncovered six major clades within the family, along with numerous unresolved taxonomic issues. Dating of cladogenetic events and ancestral range estimation traced the origin of Nemacheilidae to Indochina around 48 million years ago. Subsequently, one branch of Nemacheilidae colonised eastern, central, and northern Asia, as well as Europe, while another branch expanded into the Burmese region, the Indian subcontinent, the Near East, and northeast Africa. These expansions were facilitated by tectonic connections, favourable climatic conditions, and orogenic processes. Conversely, aridification emerged as the primary cause of extinction events. Our study marks the first comprehensive reconstruction of the evolution of Eurasian freshwater biodiversity on a continental scale and across deep geological time.

Eurasia has undergone substantial tectonic, geological, and climatic changes throughout the Cenozoic era, primarily associated with tectonic plate collisions and a global cooling trend. The evolution of present-day biodiversity unfolded in this dynamic environment, characterised by intricate interactions of abiotic factors. However, comprehensive, large-scale reconstructions illustrating the extent of these influences are lacking. We reconstructed the evolutionary history of the freshwater fish family Nemacheilidae across Eurasia and spanning most of the Cenozoic era. Molecular phylogeny uncovered six major clades within the family, along with numerous unresolved taxonomic issues. Dating of cladogenetic events and ancestral range estimation traced the origin of Nemacheilidae to Indochina around 48 million years ago. Subsequently, one branch of Nemacheilidae colonised eastern, central, and northern Asia, as well as Europe, while another branch expanded into the Burmese region, the Indian subcontinent, the Near East, and northeast Africa. These expansions were facilitated by tectonic connections, favourable climatic conditions, and orogenic processes. Conversely, aridification emerged as the primary cause of extinction events. Our study marks the first comprehensive reconstruction of the evolution of Eurasian freshwater biodiversity on a continental scale and across deep geological time.

The Schistura robertsi species complex is a group of freshwater fish inhabiting streams in southeast Myanmar as well as in western and southern Thailand. In southern Thailand, the distribution exceeds the biogeographically important ‘Surat Thani – Krabi line’. The complex is believed to include five described and one undescribed species, but monophyly and systematics of the group have never been studied explicitly. The present study aims to resolve the number of species within the Schistura robertsi group as well as their distribution areas and phylogenetic relations. We analysed mitochondrial and nuclear sequence data of 86 specimens from 47 localities and 18 morphological characters of 193 specimens. The phylogenetic analyses revealed the S. robertsi complex to be monophyletic and to be composed of ten major lineages. Six of them correspond to the known described or undescribed species, but another four newly identified clades reveal the existence of an overlooked diversity within the group. All genetic lineages are statistically highly supported and all are morphologically diagnosable, suggesting that they represent distinct species. The distribution areas of several clades overlap, the cases of direct co-occurrence show no sign of hybridisation.

Western Southeast Asia is hosting one of the world’s most diverse faunas, and one of the reasons for this huge diversity is the complex geologic past of the area, increasing the frequency of isolation and expansion events over evolutionary time scale. As an example case, the present study reveals the phylogeny and biogeographic history of the Paracanthocobitis zonalternans species complex, small benthic freshwater fish (Teleostei: Nemacheilidae) that are commonly occurring across western Southeast Asia (from central Myanmar through western and southern Thailand to northern Malaysia). The group is particularly interesting since it occurs in three biogeographic subdivisions (Burmese, Indochinese, Malay/Sundaic) and across all of the major biogeographic barriers in the region. Basing on mitochondrial and nuclear sequence data of 93 samples from about 50 localities we found six major clades, most with exclusive geographic distribution. Divergence time dated the origin of the P. zonalternans species complex to early Miocene (17.8 MYA) and a biogeographic analysis identified the Tenasserim region as the ancestral region. From this region the fish spread during periods of lowered global sea level, particularly during late Miocene (11-8 MYA) northwards into all Burmese river basins and southwards into south Thailand and northern Malaysia. Besides lowered global sea level periods, local stream capture events allowed the complex to expand, e.g. into the Mae Klong basin. Strong fragmentations during periods with elevated sea level during the Pliocene and Pleistocene repeatedly restricted populations to refuges and shaped the observed major lineages. Our results document a higher diversity within the P. zonalternans species complex than formerly believed and a strong impact of global sea level on its evolutionary history. Low sea levels promoted dispersal and elevated sea levels fragmentation events. A very similar impact of sea level changes can be expected in all stationary fauna (freshwater and terrestrial) in all non-mountainous coastal regions worldwide.

One of the most efficient mechanisms to keep animal lineages separate is a difference in ploidy level (number of whole genome copies), since hybrid offspring from parents with different ploidy level are functionally sterile. In the freshwater fish family Botiidae, ploidy difference has been held responsible for the separation of its two subfamilies, the evolutionary tetraploid Botiinae and the diploid Leptobotiinae. Diploid and tetraploid species coexist in the upper Yangtze, the Pearl River and the Red River basins in China. Interestingly, the species 'Botia' zebra from the Pearl River basin combines a number of morphological characters that otherwise are found in the diploid genus Leptobotia with morphological characters of the tetraploid genus Sinibotia, therefore the aim of the present study is to test weather 'B.' zebra is the result of a hybridisation event between species from different subfamilies with different ploidy level. A closer morphological examination indeed demonstrates a high similarity of 'B.' zebra to two co-occurring species, the diploid Leptobotia guilinensis and the tetraploid Sinibotia pulchra. These two species thus could have been the potential parental species in case of a hybrid origin of 'B.' zebra. The morphologic analysis further reveals that 'B.' zebra bears even the diagnostic characters of the genera Leptobotia (Leptobotiinae) and Sinibotia (Botiinae). In contrast, a comparison of six allozyme loci between 'B.' zebra, L. guilinensis and S. pulchra showed only similarities between 'B.' zebra and S. pulchra, not between 'B.' zebra and L. guilinensis. Six specimens of 'B.' zebra that were cytogenetically analysed were tetraploid with 4n = 100. The composition of the karyotype (18% metacentric, 18% submetacentric, 36% subtelocentric and 28% acrocentric chromosomes) differs from those of L. guilinensis (12%, 24%, 20% and 44%) and S. pulchra (20%, 26%, 28% and 26%), and cannot be obtained by any combination of genomes from L. guilinensis and S. pulchra. Phylogenetic reconstructions based on sequence data of the mitochondrial cytochrome b gene and the nuclear RAG-1 gene invariably places 'Botia' zebra as sister species to S. pulchra, while L. guilinensis is only distantly related. The presented combination of genetic data demonstrates that 'B.' zebra is not the result of a hybridisation, but a species of tetraploid genus Sinibotia with a striking morphological evolution towards an enormous similarity with a co-occurring, but not directly related species. The complete lack of knowledge of the ecology of these species, their main predators or their ecological interactions hampers any conclusion regarding the evolutionary advantage of such adaptation.

Over the years, researchers have used presumptively neutral molecular variation to infer the origins of current species' distributions in northern latitudes (especially Europe). However, several reported examples of genic and chromosomal replacements suggest that end-glacial colonizations of particular northern areas may have involved genetic input from different source populations at different times, coupled with competition and selection. We investigate the functional consequences of differences between two bank vole (Clethrionomys glareolus) haemoglobins deriving from different glacial refugia, one of which partially replaced the other in Britain during end-glacial climate warming. This allows us to examine their adaptive divergence and hence a possible role of selection in the replacement. We determine the amino acid substitution Ser52Cys in the major expressed β-globin gene as the allelic difference. We use structural modelling to reveal that the protein environment renders the 52Cys thiol a highly reactive functional group and we show its reactivity in vitro. We demonstrate that possessing the reactive thiol in haemoglobin increases the resistance of bank vole erythrocytes to oxidative stress. Our study thus provides striking evidence for physiological differences between products of genic variants that spread at the expense of one another during colonization of an area from different glacial refugia.

The study focuses on the phylogenetic origin and genetic diversity of brown trout in the eastern part of the Balkan Peninsula. It further aims to reveal the impact of human-mediated transfers and stocking with non-indigenous trout on the populations in this area. For these purposes, mtDNA control region and microsatellite variation of 204 individuals from 16 populations were analysed. The results indicate that mtDNA haplotypes from the lower Danube basin and southern Black Sea basins differ substantially from a subclade of the Danubian lineage consisting of haplotypes found so far in the most of the Danube basin and in the Caspian and Aral Sea basins. Considering also the results of demographic analyses, this study evidences a complex evolutionary history of brown trout in the southern and western parts of the Black Sea basin. In the Aegean Sea basin, a high frequency of the central haplotype of Adriatic mtDNA lineage has been found. The other Adriatic lineage haplotypes found in this basin differ from the central haplotype by one mutational step only, indicating a recent evolution of the Adriatic lineage in the Aegean Sea basin. Substantial genetic differentiation among populations and basins was revealed. The hybridization with Atlantic brown trout was indicated in both sea basins, but especially in the Danube basin. Compared to other European regions, it can be inferred that the introgression of exogenous brown trout in the eastern Balkan populations is rather low.