MATE CHOICE AND MATERNAL SELECTION FOR SPECIFIC PARASITE RESISTANCES BEFORE, DURING AND AFTER FERTILIZATION

As Hamilton and Zuk pointed out, some loci may be of special importanc e for sexual selection because they play a crucial role in the co-evol ution between parasites and hosts. In previous work I have tried to ex tend Hamilton and Zuk's parasite hypothesis for sexual selection, part ly by including findings of immunologists and endocrinologists: in som e species, handicapping signals may specifically reveal the current ne eds of the immune system which depends on the host's susceptibilities to different parasites. In other species, depending on the constellati on of some key variables, non-handicapping signals could directly reve al the identity of resistance genes. Despite the general conflict of i nterests between the sexes, sexual selection may, in these cases, lead to signallers (i.e. mostly the males) focusing on improving their off spring's survival chances instead of trying to maximize their number. Males achieve this by allowing choosy females to optimize costs and be nefits of each resistance. Both parts of the extended parasite hypothe sis suggest that female choice for specific heritable mate-qualities a im to optimize the resistance genetics of the unfertilized eggs. Howev er, intersexual selection could go further than just choosing a mate. Here, I list the possible selection levels at which the mother and/or her ova could select for specific sperm haplotypes before, during and after the formation of the zygote. For many of these possible selectio n levels, evidence suggests that selection after mating might favour h eterozygosity or even certain specific allele combinations at loci whi ch are involved in the parasite-host co-evolution (e.g. the major hist ocompatibility complex or the transferrin locus).