MACDOUGALL-SHACKLETON, E.A.; DERRYBERRY, E.P.; FOUFOPOULOS, J.; DOBSON, A.P.; HAHN, T.P.; University of Western Ontario; Duke University; University of Michigan; Princeton University; University of California, Davis: Parasite-mediated heterozygote advantage in an outbred songbird population
Coevolution with parasites is thought to maintain genetic diversity in host populations. However, while there are sound theoretical reasons to expect heterozygosity and parasite resistance to be related, this pattern has generally been shown only in inbred laboratory and island populations. This leaves doubt as to whether parasite-mediated selection for genetic diversity is in fact a general process. Here we show that haematozoan parasite load is linked to two complementary measures of microsatellite variability, in an outbred population of mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) for which we know that parasites reduce fitness. Moreover, each of the genetic measures predicts a subtly different aspect of parasitism: heterozygosity is related to the risk of parasitism, and mean d2 to the severity of infection among parasitized individuals.
