Faster male lizards are better defenders not sneakers

Abstract

Locomotion is an important trait to individual fitness in numerous animal taxa for predator escape and prey acquisition. However, the role of locomotion in mating success has been largely unexplored. Even studies linking sprint speed with proxies of fitness (e.g. dominance) and actual measures of mating success (e.g. genetic reproductive success) have struggled to test explicit hypotheses as to how high-performance individuals attain higher fitness. We studied a free-ranging population of male collared lizards, Crotaphytus collaris , to determine why faster males sire more offspring. Specifically, we tested the alternative hypotheses that faster males are ‘fast defenders’ versus ‘fast sneakers’ by using molecular genetic techniques to examine patterns of maternity and paternity in the population. We found that females that were defended by faster males had a lower proportion of offspring sired by males that did not defend them (support for a fast defender hypothesis). In contrast, we found no relation between males' sprint speed and the proportion of their offspring that were produced by females other than those they defended (no support for a fast sneaker hypothesis). In species in which locomotor performance is important to male competition, these alternative hypotheses should be simultaneously tested and complemented with behavioural data to discriminate them from female choice.