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Evolution of polyandry

Publications filtered by: Evolution of polyandry

Female crickets trade offspring viability for fecundity
Simmons, L. W. & Garcia-Gonzalez, F. 2007 Female crickets trade offspring viability for fecundity Journal of Evolutionary Biology, 20: 1617-1623
A growing number of studies are suggesting that females can improve the viability of their embryos by mating with multiple males. However, the reason why females should have low rates of embryo viability is puzzling. Here we conduct a quantitative genetic study of maternal effects on embryo viability in the field cricket Teleogryllus oceanicus. After controlling for female body size, we find significant additive genetic variance for ovary weight, a measure of fecundity, and egg hatching success, a measure of embryo viability. Moreover, we show a genetic trade-off between these traits that is predicted from life-history theory. High rates of embryo mortality in this highly fecund species might therefore be explained by selection favouring an optimum balance between fecundity and embryo viability that maximizes maternal fitness. Paternal effects on female fecundity and embryo viability are often seen as benefits driving the evolution of polyandrous behaviour. However, we raise the alternative possibility that paternal effects might shift females from their naturally selected optimum, and present some support for the notion that sexual conflict over a female’s optimal fecundity and embryo viability might generate antagonistic coevolution between the sexes.
Sources of genetic and phenotypic variance in sperm performance and larval traits in a sea urchin
Evans, J. P., Garcia-Gonzalez, F. & Marshall, D. J. 2007 Sources of genetic and phenotypic variance in sperm performance and larval traits in a sea urchin Evolution, 61: 2832-2838
In nonresource based mating systems females are thought to derive indirect genetic benefits by mating with high-quality males. Such benefits can be due either to the intrinsic genetic quality of sires or to beneficial interactions between maternal and paternal haplotypes. Animals with external fertilization and no parental care offer unrivaled opportunities to address these hypotheses. With these systems, cross-classified breeding designs and in vitro fertilization can be used to disentangle sources of genetic and environmental variance in offspring fitness. Here, we employ these approaches in the Australian sea urchin Heliocidaris erythrogramma and explore how sire–dam identities influence fertilization rates, embryo viability (survival to hatching), and metamorphosis, as well as the interrelationships between these potential fitness traits. We show that fertilization is influenced by a combination of strong maternal effects and intrinsic male effects. Our subsequent analysis of embryo viability, however, revealed a highly significant interaction between parental genotypes, indicating that partial incompatibilities can severely limit offspring survival at this life-history stage. Importantly, we detected no significant relationship between fertilization rates and embryo viability. This finding suggests that fertilization rates should not be inferred from hatching rates, which is commonly practiced in species in which it is not possible to estimate fertilization at conception. Finally, we detected significant additive genetic variance due to sires in rates of juvenile metamorphosis, and a positive correlation between fertilization rates and metamorphosis. This latter finding indicates that the performance of a male’s ejaculate in noncompetitive IVF trials predicts heritable offspring traits, although the fitness implications of variance in rates of spontaneous juvenile metamorphosis have yet to be determined.
The evolution of polyandry: intrinsic sire effects contribute to embryo viability
Garcia-Gonzalez, F. & Simmons, L. W. 2005 The evolution of polyandry: intrinsic sire effects contribute to embryo viability Journal of Evolutionary Biology, 18:1097-1103
Females typically mate with more than one male despite the costs incurred, thus questioning Bateman’s principle. A series of genetic benefits have been proposed to account for the evolution of polyandry, including the acquisition of viability genes for offspring. The ‘intrinsic male quality’ hypothesis suggests that polyandry increases the probability that females produce offspring sired by males that bestow high viability on their offspring. Heritable variation in viability is the basic requirement for the occurrence of this genetic benefit. By using a half-sib breeding design with a species of cricket in which polyandry is known to increase hatching success, we present clear experimental evidence that intrinsic male quality contributes to embryo viability. Despite recent support for the evolution of polyandry based on compatibility of genotypes between males and females, we show that hatching success is not determined by an interaction between paternal and maternal genotypes but rather that sons inherit paternal genes that influence the viability of eggs laid by their mates. Moreover, our data implicate a potential role for indirect genetic effects of male accessory gland products on embryo viability. Additive genetic contributions to embryo viability may be an important factor underlying the frequently observed benefits of polyandrous behaviour.
Sperm viability matters in insect sperm competition
Garcia-Gonzalez, F. & Simmons, L. W. 2005 Sperm viability matters in insect sperm competition Current Biology, 15: 271-275

Female promiscuity often results in the ejaculates of different males competing to fertilize a female's ova. Experimental studies in insects have shown how sperm competition can be a potent selective force acting on an array of male reproductive traits, including features of the ejaculate such as sperm numbers or sperm size. However, experimental analysis of the role of sperm quality in determining paternity in insects has been neglected, despite the fact that sperm quality has been shown to influence the outcome of sperm competition in vertebrates. A recent comparative analysis found that males of polyandrous insect species show a higher proportion of live sperm in their stores, suggesting that sperm competition has shaped the quality of insect sperm. Here we test the hypothesis that sperm viability influences paternity at the within-species level. We use the cricket Teleogryllus oceanicus to conduct sperm competition trials involving pre-screened males that differ in the viability of their sperm. We find that paternity success is determined by the proportion of live sperm in a male's ejaculate. Furthermore, we were able to predict the patterns of paternity observed on the basis of the males' relative representation of viable sperm in the female's sperm storage organ. Our findings provide the first experimental evidence for the theory that sperm competition selects for higher sperm quality in insects, and indicate that between-male variation in sperm quality needs to be considered in theoretical and experimental studies of insect sperm competition.

Infertile matings and sperm competition: the effect of non sperm representation on intraspecific variation in sperm precedence patterns
Garcia-Gonzalez, F. 2004 Infertile matings and sperm competition: the effect of "non sperm representation" on intraspecific variation in sperm precedence patterns American Naturalist, 164: 457-472

In theoretical and experimental approaches to the study of sperm competition, it is often assumed that ejaculates always contain enough sperm of good quality and that they are successfully transferred and used for fertilization. However, this view neglects the potential effects of infertility and sperm limitation. Permanent or temporal male infertility due to male sterility, insemination failures, or failures to fertilize the ova implies that some males do not achieve sperm representation in the female reproductive tract after mating. A review of the literature suggests that rates of nonsperm representation may be high; values for the proportion of infertile matings across 30 insect species vary between 0% and 63%, with the median being 22%. I simulated P2 (the proportion of offspring fathered by the second male to copulate with a female in a double-mating trial) distributions under a mechanism of random sperm mixing when sample sizes and rates of male infertility varied. The results show that nonsperm representation can be responsible for high intraspecific variance in sperm precedence patterns and that it can generate misleading interpretations about the mechanism of sperm competition. Nonsperm representation might be a common obstacle in the studies of sperm competition and postcopulatory female choice.

Variation in paternity in the field cricket Teleogryllus oceanicus: no influence of sperm numbers or sperm length
Simmons, L.W.; Wernham, J.; Garcia-Gonzalez, F. & Kamien, D. 2002 Variation in paternity in the field cricket Teleogryllus oceanicus: no influence of sperm numbers or sperm length Behavioral Ecology, 14: 539-545
Recent attention has focused on the role that sperm competition may play in the evolution of sperm morphology. Theoretical analyses predict increased sperm size, decreased sperm size, and no change in sperm size in response to sperm competition, depending on the assumptions made concerning the life history and function of sperm. However, although there is good evidence that sperm morphology varies widely within and between species, the adaptive significance of this variation has not been examined. Here we document significant intraspecific variation in sperm length in the field cricket, Teleogryllus oceanicus. Sperm length did not influence the rate of migration of sperm from the spermatophore to the female’s spermatheca. We performed sperm competition trials in which we varied the numbers of sperm transferred by each of two males that differed in the length of sperm they produced. Neither sperm length nor the number of sperm transferred influenced paternity. The same results were obtained using two different methods for assigning paternity. The distribution of paternity across a female’s mates was highly variable, with frequently one, or more in the case of females mated to four males, principal sire. There were no mating order effects on paternity. These data show that sperm do not mix randomly in the female’s spermatheca. We discuss several alternative explanations for the patterns of paternity observed.
Maternal sexual interactions affect offspring survival and ageing
Dowling, D. K., Williams, B. R., and Garcia-Gonzalez, F. 2014 Maternal sexual interactions affect offspring survival and ageing Journal of Evolutionary Biology, 27: 88-97

In many species, females exposed to increased sexual activity experience reductions in longevity. Here, in Drosophila melanogaster, we report an additional effect on females brought about by sexual interactions; an effect that spans generations. We subjected females to a sexual treatment consisting of different levels of sexual activity, and then investigated patterns of mortality in their offspring. We found reduced probabilities of survival, increases in the rate-of-senescence, and a pattern of reduced mean longevities, for offspring produced by mothers that experienced higher levels of sexual interaction. We contend that these effects constitute trans-generational costs of sexual conflict – the existence or implications of which have rarely been considered previously. Our results indicate that ongoing exposure by mothers to male pre-copulatory interactions is itself sufficient to drive trans-generational effects on offspring mortality. Thus, we show that increases in maternal sexual activity can produce trans-generational effects that permeate through to latter life-stages in the offspring. This helps to elucidate the complex interplay between sex and ageing, and provides new insights into the dynamics of adaptation under sexual selection.