PARENT-OFFSPRING REGRESSION SUGGESTS HERITABLE SUSCEPTIBILITY TO ECTOPARASITES IN A NATURAL-POPULATION OF KITTIWAKE RISSA-TRIDACTYLA

Little information is available on the genetic variability of host sus ceptibility to parasites in natural populations despite its importance for the understanding of the evolution of host-parasite interactions. A long-term demographic and epidemiologic survey of a seabird populat ion allowed us to investigate the potential correlation between parent and offspring ectoparasite load, while controlling for various enviro nmental factors. In particular, parasite loads were measured for all i ndividuals (i.e., parents and offspring) when they were nestlings and the effect of the year and breeding cliff were taken into account. The positive correlation found between parent and offspring parasite load s suggests a heritable susceptibility to ectoparasitism by ticks in th is host population and that this character has the potential to respon d to natural selection.