Fedorov V.V., Formozov N.A., Surin V.L., Val'chuk O.P., Kerimov A.B.
Zoologicheskiy zhurnal 2006; 85(5): 621-628
In the zone of overlapping their ranges (the middle Amur River basin, Pashkovo, Jewish Autonomous Region), the great tit forms major and minor hybridized with a frequency of 10% of mixed pairs (in relation to the total number of breeding pairs, including mates of major phenotype). Despite this hybridization rate, both forms maintained their specific features over many generations. To evaluate the rate of genetic introgression, the control region of mitochondrial (mt-) DNA in sympatric (74 specimens of major phenotype, 14 specimens of minor phenotype, and 6 intermediate specimens from the middle Amur River basin) and allopatric (major - 25 birds from Moscow region and 22 from the Netherlands; minor - 10 birds from Primorski Territory) populations were studied. Contrary to the author's previous hypothesis of the possible accumulation of genes minor in tits of the form major, the introgression rate was much higher in migrant minor population, than in sedentary major one. Among tits with minor phenotype, 35.7% birds had major mt-DNA, while minor mt-DNA was detected only in 6.8% birds of major appearance.
