Unexpected high fitness payoff of subordinate social tactics in male collared lizards

摘要

Sexual selection theory often predicts that dominant males will sire more offspring than males displaying subordinate social tactics. We combined the records of space use by collared lizard, Crotaphytus collaris, females and records of social and spatial behaviour of males displaying two markedly different social tactics (territorial and nonterritorial) with genetic determination of parentage to test how variation in male social tactics influences the distribution of reproductive success. In marked contrast with predictions based on their social and spatial behaviour, territorial males did not monopolize paternity of offspring with the females that they defended, and on average, nonterritorial males obtained reproductive success equal to that of territorial males, both within and among successive clutches. When all males were analysed together, none of the traits that are often hypothesized to promote fitness in other lizards were under strong sexual selection in collared lizard males. Among territory owners alone, however, there was positive directional selection on body size. Both the unexpected success of non-territorial males and exceptionally high levels of multiple paternity appear linked in part to features of the habitat at our study site that diminish the ecological potential for territorial males to monopolize mating opportunities with females that reside in their defended areas. If female collared lizards derive any fitness benefits by mating with multiple males, it is likely that these are genetic rather than material.