Towards a functional understanding of "good genes"

The Hamilton & Zuk hypothesis (1982) underpins our understanding of the rel ationship between secondary sexual characters, parasites, and immunological function. However, despite the wealth of empirical studies that attempt to address issues raised by the Hamilton a Zuk hypothesis, there have been no overt attempts to identify the "good genes" that females select or how tho se good genes influence the hose's immune system. Behavioural ecologists ha ve generally viewed this aspect of immunity as a black box. In this review we propose candidate good genes in vertebrates, discuss their role in immun e function and parasite resistance, and discuss several aspects of the assu mptions that pervade studies of parasite mediated sexual selection in verte brates. We also examine invertebrates (specifically insects) where our curr ent knowledge of these systems suggests the patterns apparent in vertebrate s are not underpinned by the same genetic mechanisms.