Balogová, M., N. Pipová, P. Papežík, M. Uhrin, I. Majláth, V. Majláthová & P. Mikulíček

Filling a gap in central Europe: morphological and genetic variation in the hybridogenetic complex of water frogs (genus Pelophylax) in Slovakia. pp. 145-159 plus Supplementary material.

Abstract. The central European complex of water frogs (Pelophylax esculentus complex) is one of the best studied hybridogenetic complexes in vertebrates, but also one of the most complicated due to different modes of hybrid reproduction. Although genetic and ecological research on water frogs has been going on for more than fifty years, many areas of Europe are still underexplored, which is also the case of eastern Slovakia. In this study, we fill this gap and investigate local populations from morphological and genetic perspectives. During field surveillance and using genetic markers, we found 146 individuals of P. ridibundus, 17 of P. lessonae and 116 diploid hybrids of P. esculentus in 21 localities. In addition to pure populations of P. ridibundus, we recorded the syntopic occurrence of hybrids with parental species. The sex ratio in parental species was equal, but females strongly dominated in hybrids. Based on several clonality tests, it can be assumed that hybrids primarily eliminate the lessonae genome during gametogenesis and form clonal gametes with the ridibundus genome. The high clonal diversity observed in the ridibundus genome of hybrids is most likely the result of multiple primary hybridization events in sympatric populations. All individuals of P. lessonae, 86.2% of P. esculentus and 8.3% of P. ridibundus had lessonae mtDNA. Introgressed individuals of P. ridibundus shared the same mitochondrial haplotypes with the two other taxa, suggesting relatively recent unidirectional introgression.

Key words. Amphibia, Anura, Ranidae, clonal reproduction, habitat preferences, haplotype diversity, hybridogenesis, mtDNA introgression, ploidy level.