Joelle Gouy de Bellocq

Parasite-mediated selection on major histocompatibility complex (MHC) genes has mainly been explored at the intraspecific level, although many molecular studies have revealed trans-species polymorphism. Interspecific patterns of MHC diversity might reveal factors responsible for the long-term evolution of MHC polymorphism. We hypothesize that host taxa harbouring high parasite diversity should exhibit high levels of MHC genetic diversity. We test this assumption using data on rodent species and their helminth parasites compiled from the literature. Controlling for similarity due to common descent, we present evidence indicating that high helminth species richness in rodent species is associated with increased MHC class II polymorphism. Our results are consistent with the idea that parasites sharing a long-term coevolutionary history with their hosts are the agents of selection explaining MHC polymorphism.

We investigated the endo- and ectoparasitic fauna of 45 specimens of Rattus rattus and 44 specimens of Mus musculus collected in Sicily. This study is the second survey of the parasitic fauna of these 2 rodent species on this Mediterranean island. Four nematode species, 1 cestode species, 2 flea species, and 1 tick species were recovered from R. rattus. Six nematode species, 3 cestode species, 1 digenean species, 1 flea species, and 1 tick species were recovered from M. musculus. As noted on other western Mediterranean islands, both rodent species show a depauperate parasite species richness in comparison with continental situations.