Experimental constraints on mate preferences inDrosophila pseudoobscuradecrease offspring viability and fitness of mated pairs

Abstract

Using Drosophila pseudoobscura, we tested the hypothesis that social constraints on the free expression of mate preferences, by both females and males, decrease offspring viability and reproductive success of mating pairs. Mate preference arenas eliminated intrasexual combat and intersexual coercion. The time female and male choosers spent in arena tests near either of two opposite-sex individuals measured the preferences of choosers. We placed choosers in breeding trials with their preferred or nonpreferred discriminatee when they met the minimum criteria for showing the same preference in two consecutive tests. There was no statistically significant difference in the frequency of female and male choosers meeting minimal preference criteria. There was a significant difference between female and male choosers for offspring viability, with female choice having the greater effect, but there was not a significant difference in the overall reproductive success of male and female choosers. There were significant differences in fitness between matings to preferred and nonpreferred partners. Female and male choosers paired with their nonpreferred discriminatees had offspring of significantly lower viability, as predicted by the constraints hypothesis. Reproductive success, our measure of overall fitness, was greater when males or females mated with the partner they preferred rather than the one they did not prefer.constraints hypothesis S ocial constraints on the free expression of mate preferences may affect offspring viability and reproductive success of choosers as suggested by commentators (1) on Partridge's (2) classic study, which was the first to associate offspring viability with mate choice. That mate preferences affect offspring viability also is an important prediction of hypotheses about the cues mediating mate preference (3), particularly those focused on mate compatibility at loci affecting immune function in offspring (4-6). Many studies have demonstrated that females prefer males with more elaborate secondary sexual characteristics (7), and other studies have shown that males with the most exaggerated secondary sexual traits are healthier than other males (8-12). However, relatively few studies (13-15) have shown benefits in offspring viability for females reproducing with males having traits preferred by most females. In contrast, recent studies on the benefits of mate preferences for choosers, without reference to traits of discriminatees that may mediate preferences, showed that mate preferences of females and males affect offspring viability (16-21), productivity of mating pairs (22), and chooser longevity (23). We tested the constraints hypothesis (24-26) that says social or ecological constraints on reproductive decisions, those that prevent individuals from reproducing with their preferred partner(s), result in lower offspring viability and lower overall reproductive success.To test predictions of the constraints hypothesis, we used the same methodology with Drosophila pseudoobscura as Drickamer ...

Reproductive decisions under ecological constraints: It's about time

“…Then, they carry out pretouching arena (such as the one pictured in ref. 46) tests, to measure the fraction of potential mates acceptable to focal individuals. Note that the experiments evaluating accept/ reject responses must be tightly controlled so that subject's responses are not contaminated by intrasexual interactions among the discriminatees or sexual coercion (55).…”

“…Additionally, until relatively recently, few data existed in support of the good genes hypothesis of mate choice. However, female and male choice studies in flies (46), cockroaches (47,48), ducks (49,50), and mice (39,51,52) have demonstrated that offspring viability was significantly higher when choosers were mated with discriminatees they preferred, as was productivity (the number of offspring surviving to reproductive age). In contrast, fecundity (the numbers of eggs laid or offspring born) was almost always lower and sometimes significantly lower when choosers were experimentally paired with partners they preferred compared with partners they did not prefer (53).…”

“…Why are these studies (39,(46)(47)(48)(49)(50)(51)(52)53) of interest in an article on sex roles? (i) They provide powerful empirical counterpoint to theory that argues that indirect fitness effects are unlikely to accrue from mate preferences.…”

Polyandry increases offspring viability and mother productivity but does not decrease mother survival in Drosophila pseudoobscura

“…This conclusion came from an experimental study in which females who copulated with the same male repeatedly compared with females who copulated only one time had a significantly higher number of offspring at the age of eclosion (5), a likely result of sperm limitation (because females do not receive enough sperm and/or that the sperm she does receive are inviable) in single mated females. Previous mate choice studies in D. pseudoobscura (22)(23)(24) showed that females and males paired with their individually preferred partners had offspring with higher egg-to-adult survival, higher numbers of eclosed offspring (i.e., productivity), and higher net reproductive success than individuals constrained to pairings with their nonpreferred partners. Because mating with preferred partners in nature may be constrained by dispersal limitation or social competition or sexual coercion (25), the constrained female hypothesis (7,26) predicts that a benefit of polyandry beyond that from multiply mating with the same male is enhanced offspring health.…”

Polyandry enhances offspring viability with survival costs to mothers only when mating exclusively with virgin males in Drosophila melanogaster

“…The differences indicate an advantage in egg number for M L females at younger ages and P E females at older ages, therefore, given our interest in offspring viability, we truncated the comparison of offspring viability to subjects less than 43 days old: On 28 of 36 days difference scores were positive indicating greater egg‐to‐adult survival for P E than M L females. Assuming that M L females had stronger constraints on mate choice than P E females, the over‐lifetime observations of P E advantage over M L are consistent with the hypothesis (Anderson et al., 2007; Gowaty, 2008; Gowaty et al., 2007a) saying that females breeding under constraints compensate for expected deficits in health of offspring by increasing egg number.…”