Susceptibility to intestinal parasites and juvenile survival are correlated with multilocus microsatellite heterozygosity in the Capercaillie (Tetrao urogallus)

Abstract

Inbreeding can have a negative influence on several life-history traits as well as disease resistance in birds and mammals through different geneticmechanisms. Endangered and declining populationsmay be at particular risk for inbreeding. The level of inbreeding can be estimated by assessing individual heterozygosity at neutralmicrosatellitemarkers.We studied the relationships between intestinal helminth infections, age, sex and heterozygosity in Capercaillie (Tetrao urogallus).We assessedmicrosatellite heterozygosity at eight autosomal loci and calculated two different indices (multilocus heterozygosity MLH and mean d 2) to quantify individual heterozygosity. Capercaillie were infected by three species of cestodes (Paroniella urogalli, Skrjabinia cesticillus and Hymenolepis sp.) and one nematode species (Ascaridia compar).We found that the probability of nematode infection decreased as the level of heterozygosity (measured by mean d 2) increased. Also, the intensity of nematode infection decreased as heterozygosity (measured by MLH) increased. However, we did not observe correlation between heterozygosity and the occurrence of cestodes. In addition, heterozygosity (bothMLHandmean d 2)was dependent on age class: adultCapercaillie had higher heterozygosity than juveniles. Results suggest selection for heterozygosity which can be reinforced by differences in genetic parasite resistance.