Abstract
MHC genes form essential part of adaptive immunity and as the most polymorphic genes have attracted interest of evolutionary biologists during the last decades. MHC studies in wild organisms pose a challenge due to extreme numbers of alleles and frequent loci duplications, and hence the low diversity and non-duplicated nature of the Eurasian beaver (Castor fiber) MHC seem to provide a useful unique model.
The Eurasian beaver undergone dramatic bottleneck culminating at the end of the 19th century, when only 1200 individuals were surviving, with these scattered in several different locations. Subsequently it was followed by a phenomenal re-expansion supported by multiple reintroductions.
As a result, beavers of various origin meet in newly-established populations. We aim to demonstrate how the different periods influenced MHC variability in beavers using sequences of DRB and DQA loci.
While the allele sequences show signs of both positive and balancing selection in the past pre-bottleneck times, the reduced variability illustrates the effect of drift during the bottleneck. Moreover, the signal of divergent allele advantage suggests the importance of re-established selection in the present-day populations.