ИСТИНА

The differences in the songs structures are widely recognized to be a key factors in reproductive isolation in songbirds. Acoustic relationships between closely related taxa in zones of contact and hybridization provide an extremely interesting but still poorly studied problem. There are a number of intriguing subjects concerning these relationships such as mixed singing, asymmetric vocal copying, dependencies between acoustic and genetic traits. We analyze these issues based on our genetic and bio-acoustic researches in the areas of contact and hybridization between European and Siberian Chiffchaff in South Ural, Western and Eastern Greenish Warbler in Sayan Mountains, Thrush and common Nightingale in southern Russia. In all zones studied, no clear evidences of song divergence between co-occurring taxa were registered while the mixed singing was found to be very common phenomenon. The convergence characteristics of the song occurs at the frequency-temporal and syntactic parameters. In mixed populations of the Chiffchaff in addition to individuals with a mixed singing, there are also bilingual individuals performing typical songs of both taxa alternately. In playback experiments, the males of Chiffchaff and Greenish Warbler tested in contact zones vigorously responded to the non-conspecific song while no male tested in allopatric populations did responded to the latter. In the zones of hybridization, the vast majority of males performs the song matching to their genotypic characteristics as they were determined by mtDNA analysis. The mismatches between gaplotypes and morphology (body measurements and plumage coloration) were found to be much more frequent. Thus our data suggest that song dialects in Chiffchaffs are determined primarily on the genetic level.