Geographic peculiarities of structure and hemicloning reproduction of Pelophylax esculentus water frog complex (Anura, Ranidae) populations in the East European Plain within Ukraine

<p>Geographic peculiarities of population structure and hemicloning reproduction of the water frog <em>Pelophylax esculentus</em> complex of 904 samples within southern East European Plain were analyzed. The proportion of populations of <em>P. ridibundus</em> is 0.667 against those 0.042 of <em>P. lessonae</em>. The RE-type populations are the most common among mixed ones (0.153). The colonies of the two parental species and <em>P.</em> kl. <em>esculentus </em>(REL-type), as well as those of <em>P. lessonae</em> with <em>P.</em> kl. <em>esculentus </em>(LE-type), have the frequencies 0.072 and 0.046, respectively. All-hybrid populations (E-type) are not numerous across the region (0.017). In the populations of Central, Northern and Western Ukraine, the <em>P. lessonae</em> genome is eliminated during gametogenesis within hybrids while in the Lower Dnieper and Lower Danube drainages, genome of <em>P. ridibundus</em> is eliminated. In the Eastern Ukraine populations, hybrids usually produce diploid gametes or haploid gametes with the <em>P. ridibundus</em> genome, less often with the chromosome set of <em>P. lessonae</em> only, and even more rarely a mixture of different types of gametes. The predominance of <em>P. ridibundus</em> in hybrid communities and the elimination of the <em>P. lessonae</em> genome in hybrids inevitably leads to the transformation of hybrid populations into “pure” R-type populations. This circumstance makes hybridization with <em>P. ridibundus</em> a factor in the shrinking of <em>P. lessonae</em> populations. That trend is especially expressed in the Forest steppe zone, where hybridization proceeds most intensively, the <em>P. lessonae</em> genome is eliminated in hybrids, and unstable populations with a numerical superiority of <em>P. ridibundus</em> predominate. </p>