Interrelationships between two bunting species (Yellowhammer Emberiza citrinella and Pine Bunting E-leucocephalos) interbreeding in zones of their ranges overlap [Russian]

摘要

The temporal and spatial dynamics of the Yellowhammer and Pine Bunting hybridization were monitored based on the museum collections and the results of the authors' field studies in Siberia. A scenario is suggested, according to which an initial contact between the species took place in the southeastern part of Western Siberia and adjacent northwestern foothills of the Altai Mountains. By now, the hybridization has resulted in the intensive introgression, so that in some places process of the species fusion is in progress. From these areas, over the 20(th) century, the hybridogenous populations with general phenotypic E. citrinella constitution expanded their ranges westward and, especially, into eastward the original E. leucocephalos range. At the easternmost border of the present contact zone (Baikal Lake region), the hybridogenous populations of the "citrinella" type turned out to be isolated reproductively from those of the local E. leucocephalos. In this region, the hybridization is occasional, but according to the scenario, it will be intensified with time. The data obtained support the hypothesis that under the secondary contact between closely related species, the occasional hybrodization will develop into mass interbreeding and then into introgressive one. The differences in species-specific songs of both species decrease over the whole sympatry zone.