Consequences of anthropogenic hybridization in wild red-legged partridge (Alectoris rufa) populations

Resumen del trabajo presentado al XXXth International Union of Game Biologists and Perdix XIII, celebrados en Barcelona (España) del 5 al 9 de septiembre de 2011.Hybridization and introgression can threat natural populations, especially when they occur as a consequence of human activities. Populations of wild red-legged partridge (Alectoris rufa) have recently declined and the release of farm-reared partridges has become a widespread strategy. Although wild red-legged and chukar partridge (A. chukar) do not breed in sympatry, captive red-legged partridges have often been hybridized with chukar partridges to increase their productivity, and hence game releases have spread hybrid birds into the wild. In this study, we investigated the occurrence of hybrids and differences in the fitness (survival and breeding) between hybrid and “pure” red-legged partridges to evaluate the consequences of genetic introgression into a wild population located in central Spain. We captured 115 wild red-legged partridges in late winter/early spring (fieldwork was carried out in February-October 2003-2005), among four game estates (central Spain; 38º 80´ N, 3º 80´ W, 610 m a.s.l.) with three different hunting management policies. To detect introgression, we used 8 diagnostic microsatellite loci and a cytochrome b sequence. We found introgression in 28.7 % wild partridges. We used generalized lineal models. The proportion of hybrids was higher among estates where restocking with farm-reared birds was conducted. Incubation probability was similar in hybrids and “pure” partridges. Hybrid females laid larger clutches than “pure” ones, but hatching success did not differ between hybrid and “pure” partridges. Hybrid birds had lower survival rate than “pure” ones, mainly because of higher predation rates. Our results show that, despite lower survival, hybrid partridges breed in natural populations and confirm a serious risk of genetic contamination of wild pure partridge populations, because of widespread releasing of farmed hybrid birds. Controlling introgression from allochthonous genomes is of vital importance for red-legged partridge long-term conservation.Peer Reviewe