Genetic variability and parasite resistance in a wild ungulate population

Multilocus heterozygosity (MLH) is the standardized average observed heterozygosity among all microsatellite marker loci in one individual. MLH declines due to inbreeding, and negative associations between MLH and fitness reported in various vertebrate taxa are thought to reflect inbreeding depression (i.e. the reduction in fitness arising in inbred individuals). Here we report preliminary results on the relationships between MLH and parasite resistance in a population of free-ranging alpine ibex (Capra ibex) in the Gran Paradiso National Park (north-western Italian Alps). We used faecal counts of nematode eggs (FEC) as an indicator of parasite resistance. FEC analyses were performed on fresh faeces collected every two weeks over four summers (2000-2003) from individually marked male alpine ibex. MLH was estimated based on 32 microsatellite loci. No significant relationship between FEC and MLH was found. Statistical power was extremely low, despite sample size and number of loci was larger than in most other studies. The estimated needed sample size was way larger than what is normally possible to obtain in most studies on wild endagered populations. Information on inbreeding-fitness correlations can be vital to direct mangement and conservation efforts on endagered species. A sufficient sample size, however, may in many cases not be reachable in this kind of studies.