Genetic and morphological data describing the hybrid zone between Bufo bufo (Linnaeus, 1758) and Bufo verrucosissimus (Pallas, 1814) in Northeastern Anatolia

The purpose of the thesis is identifying potential contact areas between the Bufo bufo and B. verrucosissimus species within the boundaries of Rize and Artvin in northeastern Türkiye, as well as the expected hybridization patterns in these areas. The method is composed of four main sections as fieldwork, mtDNA analysis, microsatellite DNA analysis, and morphological analyses. In this content, 22 different populations were sampled from 16 different districts in Artvin and Rize provinces. To determine phylogeographic patterns and contact regions, 65 samples were examined by phylogenetic and demographic analyses based on Cytochrome b gene region sequences. To reveal the hybrid zone between species, 201 individuals were genotyped using 14 microsatellite loci based on multiplex PCR technique. The obtained data were examined using structural and spatial analyses and evaluated within the framework of the clin concept. To understand morphological differences between pure species and hybrids, 145 adult individuals representing all populations were subjected to univariate and multivariate analyses using 31 different morphological characters. According to mtDNA analyses, Pazar, Hemşin and Çamlıhemşin were determined as the districts with mitochondrial haplotypes belonging to both taxa and formed contact areas. According to demographic analyses, glacial cycles that occurred during the Quaternary Period shaped the expansion patterns of these species, and secondary contact was established following the end of the glacial periods. Microsatellite based analyses revealed the presence of a hybrid zone for the first time exhibiting a narrow and bimodal pattern classified as a tension zone, around the Yaylacılar Village of Fındıklı district. The strong selection pressure and limited introgression obviously validated that these taxa are distinct species. According to microsatellite data, B. bufo species was distributed in Rize whereas B. verrucosissimus species was distributed in Artvin. The asymmetric patterns aroused between nuclear and mitochondrial markers suggested that it may have occurred due to the ongoing expansion of B. bufo species due to the male biased dispersal or a historically eastward hybrid zone movement. Morphological analyses showed that pure species diverged in eyes, inner metatarsal tubercle, and parotoids, but these characters were not as diagnostic for hybrids.