Sexual selection on female collared lizards favours offspring production with multiple males

Abstract

Females in diverse vertebrate and invertebrate clades often mate and produce offspring with multiple male partners. Deciphering the evolutionary mechanisms underlying the origins of females producing offspring with multiple sires remains a challenging problem, because a single male can usually provide enough sperm to fertilize all eggs produced by individual females. We tested the hypothesis that having multiple males sire individual clutches is adaptive for female eastern collared lizards, Crotaphytus collaris, by examining both the fitness costs and benefits for females of producing offspring with one versus multiple male partners. We found no support for the hypothesis that females produce offspring with multiple sires to acquire access to higher-quality food resources or refuges. However, hatching success of clutches increased with the number of males that inseminated eggs, which suggests that accepting sperm from multiple males may improve offspring hatching success through one or more mechanisms. Our results also indicate that females producing offspring with multiple male partners gained genetic advantages. Although offspring mortality from clutches sired by one versus multiple males was similar, females producing clutches sired by multiple males had more total offspring that survived to maturity, resulting in a net fitness advantage for these females. Our results suggest that producing offspring with multiple males is adaptive for female collared lizards because it promotes acquisition of several fitness benefits.