Male Genotype Affects Female Longevity in Drosophila Melanogaster

Abstract

Abstract. While it is widely recognized that the manner in which organisms adjust their timing of reproduction reflects evolutionary strategies aimed at minimizing offspring mortality or maximizing reproductive output, the conditions under which the evolutionarily stable strategy involves synchronous or asynchronous reproduction is a matter of considerable discord. A recent theoretical model predicts that whether a population displays reproductive synchrony or asynchrony will depend on the relative scales of intrinsic regulation and environmental disturbance experienced by reproducing individuals. This model predicts that, under conditions of negligible competition and large-scale environmental perturbation, evolution of a single mixed strategy will result in asynchronous reproduction. We tested this prediction using empirical data on large-scale climatic fluctuation and the annual timing of reproduction by three species of flowering plants covering 1300-population-years and four degrees of latitude in Norway. In agreement with model predictions, within populations of all three species reproductive asynchrony increased with the magnitude of large-scale climatic perturbation, but bore no relation to the strength of local density dependence. These results suggest that mixed evolutionarily stable strategies can arise from the interplay of combinations of agents of selection and the scale at which they operate; hence it is fruitless to associate synchronous versus asynchronous timing with particular single factors like climate, competition, or predation. An aspect of life-history theory that has received considerable focus in both empirical and theoretical studies is the evolution of the timing and synchrony of reproduction. This undoubtedly reflects the widespread observation that timing of reproduction is a strong determinant of offspring viability and reproductive success both in animals (Lack 1950; Berger 1992;Landa 1992;Brinkhof et al. 1993;Sih and Moore 1993;Trites and Antonelis 1994;Olsson and Shine 1997; Bowyer et al. 1998;Post and Klein 1999) and plants (Janzen 1976;Harper 1977;Dieringer 1991;Young and Augspurger 1991;Domínguez and Dirzo 1995). However, the conditions under which the evolutionarily stable strategy (ESS) of the timing of reproduction involves synchrony or asynchrony within populations is a matter of debate.For example, synchronous reproduction may be favored in both seasonal and aseasonal environments, depending on whether natural selection operates on the entrainment of individuals within the population to environmental cues (resulting in an optimal date of reproduction), or whether competition and predation are important agents of offspring mortality (Ims 1990). Reproductive synchrony is not the only ESS in seasonal environments, however, because asynchronous reproduction can also be favored in seasonal environments if competition reduces both food availability and neonatal growth (Iwasa 1991;Ezoe 1995).This disparity of views on factors shaping the timing and synchrony of reproduction h...

Assessing the Potential for an Ongoing Arms Race Within and Between the Sexes: Selection and Heritable Variation

“…Our study corroborates previous studies by showing a negative correlation between fidelity and female lifespan (Civetta and Clark 2000) and no correlation between P 2 and female lifespan (Civetta and Clark 2000;Sawby and Hughes 2001). Because our study used completely outbred flies, and the earlier studies used lines homozygous for 40% of their genome, the congruence of results suggests that inbreeding depression alone cannot account for genetic variation in maleinduced harm to their mates' survival.…”

“…In species where males rarely engage in agonistic interactions, male offense and defense phenotypes are mediated predominantly by male-induced changes of female behavior and reproductive physiology. As a consequence, adaptations by males to increase offense or defense may commonly influence the fitness of females via pleiotropy (Parker 1979;Wolfner 1997;Fowler and Partridge 1989;Rice 1996;Holland and Rice 1999;Civetta and Clark 2000;Prout and Clark 2000;Sawby and Hughes 2001;Chapman 2001;Chapman et al 2003). 3 Present address: Animal Ecology, Department of Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, 752 36 Uppsala, Sweden; E-mail: urban.friberg@ebc.uu.se.…”

Genetic Variation in Male and Female Reproductive Characters Associated with Sexual Conflict in Drosophila melanogaster

“…It is worth noting that the female lifespan reducing effect that males had (henceforth, male harm to females) differed in the two exposure treatments, since the effects across male genotypes were uncorrelated in these two environments. I suggest that the effects seen in the limited exposure treatment were, at least on a relative scale, primarily due to the deleterious effects of the seminal fluid (see Chapman et al, 1995;Civetta and Clark, 2000;Sawby and Hughes, 2001). In the lifetime exposure treatment, in contrast, effects of the seminal fluid per se were no doubt augmented to a much higher degree by the costs of remating and male harassment (Fowler and Partridge, 1989;Partridge and Fowler, 1990).…”

“…First, in fruit fly populations cultured under these conditions, with overlapping generations, the phenotypic correlation between lifespan and female fitness is very high, ranging from r = 0.67-0.76 (Friberg and Arnqvist, 2003;Kidwell and Malick, 1967;Partridge, 1988;Tantawy and Rakha, 1964). Second, most studies of sexually antagonistic effects of male adaptations in Drosophila have documented effects primarily on female lifespan rather than, for example, age-specific fecundities (Friberg and Arnqvist, 2003;Rice, 1996;Sawby and Hughes, 2001;Wigby and Chapman, 2004).…”

“…Several recent studies of this species have revealed substantial costs to females, in terms of reduced lifespan and lifetime fecundity, imposed by males. For example, females mated to normal males have reduced lifespan compared to females mated to males that lack accessory gland proteins in their ejaculate (Chapman et al, 1995) and male genotypes differentially affect female lifespan after only one mating Sawby and Hughes, 2001). Further, fecundity and lifespan of females continuously housed with males vary with male phenotype, where larger males impose higher costs to females primarily as a result of elevated courtship and mating (Friberg and Arnqvist, 2003;Pitnick and Garcı´a-Gonza´lez, 2002).…”