On morphology and genetics of a successfully restored beaver population in Lithuania
At least six centres of spread of reintroduced or naturally immigrated animals have influenced the formation of the present beaver (Castor fiber) population in Lithuania. Phenetic (non-metrics of skull) and genetic (allozyme electrophoresis) analyses show that beaver subpopulations of different origin have preserved their specificity even in conditions of dense population, 30-40 years since the first releases and arrivals. This specificity might be the result of the founder effect in small geographically and temporally isolated groups of reintroduced beavers. Conversely, subpopulations from the supposed zone of intensive hybridisation were found to be very phenetically similar. Metric parameters of the skull varied slightly among subpopulations, showing the higher metric differentiation between reintroduced beavers and natural immigrants. However, beaver skulls from Lithuania were found to be significantly larger than those from the basic maternal population in the Gomel region (Belarus) and of similar size when compared with the skulls from the Voronezh population (Russia). Our investigations show the complicated morphological and genetic structure of a hybrid beaver population and its considerable morphological changes in comparison with the maternal populations.