Genetic diversity of Great Cormorants Phalacrocorax carbo in the eastern Baltic region

Abstract

A rapid expansion of the continental subspecies of the Great Cormorant (Phalacrocorax carbo sinensis) has been recorded in Europe since the 1980s. Evaluation of genetic variability of the  Great Cormorant using molecular markers is necessary for investigation of the mechanisms of formation of the newly established breeding populations in the  eastern Baltic region (in the Kaliningrad region of Russia and in Lithuania). The  samples for molecular investigation were collected in the largest breeding colonies of Great Cormorants located on the coast of the Curonian Lagoon of the Baltic Sea and in their smaller, later formed breeding colonies located in the continental part of Lithuania. After sequencing and alignment of partial fragments of mtDNA control region, 21 different haplotypes, including 8 new haplotypes never identified before, and 13 haplotypes described earlier were found. They were distributed with different frequency in different sampling sites. The haplotype network constructed using 342 bp D-loop sequences identified during the  current study and all available sequences of Great Cormorants deposited in GenBank by previous investigators revealed haplotypes attributed to subspecies P. c. sinensis being distinguished from haplotypes of subspecies P. c. carbo in the separate part of haplotype network. The newly described haplotypes did not form a phylogenetically uniform group indicating possible colonization of the Kaliningrad region and the continental part of Lithuania by individuals descending from the  largest breeding colonies spread at the  coast zone of the  Baltic Sea. A  high level of genetic population diversity in different breeding colonies recorded in the Kaliningrad region and in eastern Lithuania confirms the formation of a highly variable and well-adapted population of the Great Cormorant participating in the process of colonization of new breeding areas in the Baltic region.