Extrapair paternity in Parus major

Mating systems, as an evolutionary stable strategy, play an important role in animal reproductive process and result from an animal’s adaption to their environment, including their inter-specific environment. In the 1980s, extrapair paternity (EPP) was first noted in the eurychoric species, the Great Tit, Parus major. As earlier studies indicated, morphology, physiology, behavior, ecological characteristics and mating systems of eurychoric species differ greatly between areas or populations. Accordingly, we analyzed the mating system of the Great Tit (P.m.minor) in Fairy Cave National Nature Reserve, Liaoning, China. We collected total parent-offspring blood samples from 22 broods. We used 8 hypervariable loci, which were selected from 11 reported microsatellite loci for paternity test. In conjunction with the known genetic pattern of the female parent, the accuracy of the paternity testing reached 99.98% with this genetic data. Results of paternity testing showed that 7 of 22 broods (31.8%) had extra-pair nestling, with 16 of 197 nestlings (8.12%) a result of extra-pair fertilizations. The EPP rate of the Great Tit we noted in Liaoning is obviously lower than those in other passerine forest birds (less than 10%). Though between 55.6% and 9.1% extrapair offspring were found among the different nests, we were, however, unable to find any explanatory rule.