PARASITES, AGE AND THE HAMILTON-ZUK HYPOTHESIS - INFERENTIAL FALLACY

Hamilton and Zuk's hypothesis suggests that male showiness allows fema les to assess male's ability to resist parasites. In this hypothesis t he full expression of secondary sexual traits and parasite load are re spectively assumed to mainly depend on individual vigour and genetic r esistance. Here, we propose that a negative correlation between bright ness and parasite load can incorrectly suggest a causal relationship b etween parasitism and mating success. Parasitism can negatively covary with host age in certain circumstances of host mortality induced by p arasite accumulation, while both male brightness and female preference s positively covary with age. Thus some properties of host-parasites a ssociations, coupled with host reproductive behaviour can provide fort uitous support for the Hamilton-Zuk hypothesis.