Ectoparasite infestation and sex-biased local recruitment of hosts

Dispersal patterns of organisms are a fundamental aspect of their ecology, modifying the genetic and social structure of local populations(1-4). Paras ites reduce the reproductive success and survival of hosts and thereby exer t selection pressure on host life-history traits(4-6), possibly affecting h ost dispersal(7-9). Here we test experimentally whether infestation by hen fleas, Ceratophyllus gallinae, affects sex-related recruitment of great tit , Parus major, fledglings. Using sex-specific DNA markers, we show that fle a infestation led to a higher proportion of male fledglings recruiting in t he local population in one year. In infested broods, the proportion of male recruits increased with brood size over a three year period, whereas the p roportion of male recruits from uninfested broods decreased with brood size . Natal dispersal distances of recruits from infested nests were shorter th an those from uninfested nests(10). To our knowledge, this study provides t he first evidence for parasite-mediated host natal dispersal and local recr uitment in relation to sex. Current theory needs to consider parasites as p otentially important factors shaping life-history traits associated with ho st dispersal.