Polyandry and Fitness of Offspring Reared Under Varying Nutritional Stress in Decorated Crickets

Abstract

Females, by mating with more than one male in their lifetime, may reduce their risk of receiving sperm from genetically incompatible sires or increase their prospects of obtaining sperm from genetically superior sires. Although there is evidence of both kinds of genetic benefits in crickets, their relative importance remains unclear, and the extent to which experimentally manipulated levels of polyandry in the laboratory correspond to those that occur in nature remain unknown. We measured lifetime polyandry of free-living female decorated crickets, Gryllodes sigillatus, and conducted an experiment to determine whether polyandry leads to an increase in offspring viability. We experimentally manipulated both the levels of polyandry and opportunities for females to select among males, randomly allocating the offspring of experimental females to high-food-stress or low-food-stress regimes to complete their development. Females exhibited a high degree of polyandry, mating on average with more than seven different males during their lifetime and up to as many as 15. Polyandry had no effect on either the developmental time or survival of offspring. However, polyandrous females produced significantly heavier sons than those of monandrous females, although there was no difference in the adult mass of daughters. There was no significant interaction between mating treatment and offspring nutritional regimen in their effects on offspring mass, suggesting that benefits accruing to female polyandry are independent of the environment in which offspring develop. The sex difference in the extent to which male and female offspring benefit via their mother's polyandry may reflect possible differences in the fitness returns from sons and daughters. The larger mass gain shown by sons of polyandrous females probably leads to their increased reproductive success, either because of their increased success in sperm competition or because of their increased life span.

Polyandry Promotes Enhanced Offspring Survival in Decorated Crickets

“…Although the results of our study add to a growing body of evidence that genetic benefits play a paramount role in the evolution of polyandry in crickets Wedell 1998, 2002;Simmons 2001;Sakaluk et al 2002), the fitness benefits that females obtain vary both across species and between studies of the same species. For example, some studies have demonstrated an increase in hatching success with an increase in polyandry, but no increase in offspring viability or performance (Tregenza and Wedell 1998;Simmons 2001), whereas others have failed to detect any effect on hatching success, but have reported significant effects on offspring quality (Simmons 1988;Sakaluk et al 2002); one study has reported positive effects of polyandry on both hatching success and offspring quality (Fedorka and Mousseau 2002).…”

“…In distinguishing between two of the major classes of indirect genetic benefits, the avoidance of genetic incompatibility and the acquisition of ''good genes'' (review in Zeh and Zeh 2003), it has become customary to attribute any increase in hatching success resulting from polyandry to a reduction in genetic incompatibility, whereas any increases in offspring viability and performance are typically attributed to genes obtained from superior sires (e.g., Tregenza and Wedell 1998;Kempenaers et al 1999;Simmons 2001;Sakaluk et al 2002). However, this distinction is probably overly simplistic because the effects of genetic incompatibility and ''good genes'' can be manifest at any stage of reproduction.…”

“…For example, some studies have demonstrated an increase in hatching success with an increase in polyandry, but no increase in offspring viability or performance (Tregenza and Wedell 1998;Simmons 2001), whereas others have failed to detect any effect on hatching success, but have reported significant effects on offspring quality (Simmons 1988;Sakaluk et al 2002); one study has reported positive effects of polyandry on both hatching success and offspring quality (Fedorka and Mousseau 2002). In a previous study of G. sigillatus, Sakaluk et al (2002) found that the mass of male offspring increased with increasing opportunities for female polyandry, but they detected no effect on offspring survival, contrary to the present study. Although the earlier study did not control for number of matings, there were also a number of differences with respect to the environmental conditions under which females were maintained (e.g., temperature, photoperiod).…”

“…Some studies have not controlled for the number of matings experienced by females (e.g., Simmons 1988;Sakaluk et al 2002), or have not included treatments involving females mating repeatedly with the same male or treatments involving females mating with different males (Keil and Sachser 1998;Watson 1998;Vahed 2003). While other studies strongly suggest a genetic rather than material benefit to polyandry, other explanations cannot be completely ruled out, as the inferences rely on correlation (i.e., number of partners or amount of extrapair paternity correlated to some aspect of offspring viability or quality) (see Madsen et al 1992;Olsson et al 1994; and see Griffith et al 2002 for discussion of this problem in studies involving birds).…”

Good genes and the maternal effects of polyandry on offspring reproductive success in the bulb mite

“…Provided that there is enough genetic variance for mate quality (or compatibility), genetic benefits will always accompany any direct benefits ( Jennions & Petrie 2000;Fedorka & Mousseau 2002). Studies that have found some support for genetic benefits tested the prediction that polyandrous females should have fitter progeny than monogamous females (Madsen et al 1992;Olsson et al 1996;Watson 1998;Tregenza & Wedell 1998;Evans & Magurran 2000;Bernasconi & Keller 2001;Konior et al 2001;Fedorka & Mousseau 2002;Pai & Yan 2002;Sakaluk et al 2002;Kamimura 2003). However, the increased opportunity to choose a mate by polyandrous females could influence their investment in their progeny (Simmons 1987;Wedell 1996;Pearse et al 2002).…”