Mate choice for non-additive genetic benefits: a resolution to the lek paradox.
ABSTRACT In promiscuous mating systems, females often show a consistent preference to mate with one or a few males, presumably to acquire heritable genetic benefits for their offspring. However, strong directional selection should deplete additive genetic variation in fitness and consequently any benefit to expressing the preference by females (referred to as the lek paradox). Here, we provide a novel resolution that examines non-additive genetic benefits, such as overdominance or inbreeding, as a source of genetic variation. Focusing on the inbreeding coefficient f and overdominance effects, we use dynamic models to show that (1) f can be inherited from sire to offspring, (2) populations with females that express a mating preferences for outbred males (low f) maintain higher genetic variation than populations with females that mate randomly, and (3) preference alleles for outbred males can invade populations even when the alleles are associated with a fecundity cost. We show that non-additive genetic variation due to overdominance can be converted to additive genetic variation and becomes "heritable" when the frequencies of alternative homozygous genotypes at fitness loci deviate from equality. Unlike previous models that assume an infinite population size, we now show that genetic drift in finite populations can lead to the necessary deviations in the frequencies of homozygous genotypes. We also show that the "heritability of f," and hence the benefit to a mating preference for non-additive genetic benefits, is highest in small populations and populations in which a smaller number of loci contribute to fitness via overdominance. Our model contributes to the solution of the lek paradox.
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ABSTRACT: Females of many animals mate with more than one male even when it is costly. We conducted experiments to evaluate the benefits of mating with multiple males, using naturally occurring pairs of horseshoe crabs. We found that egg development increased with additional males for some female types, but not for others. Further, we show that male quality and compatibility between pairs may provide an advantage to offset the costs of multiple mating in this system.Females of many species mate with multiple males even when it is costly. Multiple mating may allow females to exploit postcopulatory mechanisms to ensure that their eggs are fertilized by high quality (good genes) and/or genetically compatible males. We conducted a series of noncompetitive in vitro fertilization experiments to evaluate the benefits of polyandry in naturally occurring pairs of horseshoe crabs, Limulus polyphemus. In this externally fertilizing species, attached pairs migrate to shore to spawn; unpaired males are attracted to spawning pairs by visual and chemical cues and become satellites of some (polyandrous) females while ignoring others (monandrous). When present, satellites may fertilize a high proportion of the females eggs, but their presence is costly to female nesting success. We measured developmental success for monandrous and polyandrous females crossed with attached and satellite males. We found that satellite males increased the success of polyandrous but not monandrous females. We then examined the effect of good genes and genetic compatibility on developmental success and offspring size using a North Carolina II breeding design. Results indicate that both incompatibilities between males and females and paternal good genes effects may provide a selective advantage that offsets the costs of multiple mating in this species.Behavioral Ecology 08/2013; 24(5):1218-1228. DOI:10.1093/beheco/art056 · 3.16 Impact Factor
Canadian Journal of Fisheries and Aquatic Sciences 01/2015; DOI:10.1139/cjfas-2014-0472 · 2.28 Impact Factor