Abstract
Polyandry, female mating with multiple males, is widespread across many taxa and almost ubiquitous in insects. This conflicts with the traditional idea that females are constrained by their comparatively large investment in each offspring, and so should only need to mate once or a few times. Females may need to mate multiply to gain sufficient sperm supplies to maintain their fertility, especially in species in which male promiscuity results in division of their ejaculate among many females. Here, we take a novel approach, utilizing wild‐caught individuals to explore how natural variation among females and males influences fertility gains for females. We studied this in the Malaysian stalk‐eyed fly species Teleopsis dalmanni. After an additional mating, females benefit from greatly increased fertility (proportion fertile eggs). Gains from multiple mating are not uniform across females; they are greatest when females have high fecundity or low fertility. Fertility gains also vary spatially, as we find an additional strong effect of the stream from which females were collected. Responses were unaffected by male mating history (males kept with females or in male‐only groups). Recent male mating may be of lesser importance because males in many species, including T. dalmanni, partition their ejaculate to maintain their fertility over many matings. This study highlights the importance of complementing laboratory studies with data on wild‐caught populations, where there is considerable heterogeneity between individuals. Future research should focus on environmental, demographic and genetic factors that are likely to significantly influence variation in individual female fecundity and fertility.
Highlights
Female mating with multiple males is found widely across many taxa and is almost ubiquitous in insects (Arnqvist & Nilsson, 2000)
The direct fertility benefit that a female gains from an extra mating will not be a static quantity but will depend on the context in which mating takes place. We examined how these two factors alter the benefits of female remating by means of experimentation in the wild using the Malaysian stalk-eyed fly Teleopsis dalmani (Diptera, Diopsidae)
We modeled the direction of change in individual fertility using a generalized linear mixed-effects models (GLMMs) with a binomial distribution, where changes were coded as 1 s and 0 s
Summary
Female mating with multiple males (polyandry) is found widely across many taxa (mammals: Clutton-Brock, 1989; Ginsberg & Huck, 1989; birds: Griffith, Owens, & Thuman, 2002; fishes: Avise, Jones, Walker, & DeWoody, 2002; general: Jennions & Petrie, 2000; Zeh & Zeh, 2001) and is almost ubiquitous in insects (Arnqvist & Nilsson, 2000). Laboratory studies need to be complemented by experiments conducted on wild-caught individuals, in situations that more closely replicate the natural range of conditions of female and male encounters We apply these principles to consider the consequences of multiple mating on female fertility in the Malaysian stalk-eyed fly Teleopsis dalmanni, when females vary in the degree of sperm limitation. As well as few sperm, the small size of male ejaculates is unlikely to provide any nonsperm benefits (Kotrba, 1996) Given these patterns in stalk-eyed flies, we expect to find that female T. dalmanni remate to gain direct fertility benefits. These experiments allow us to examine, using wild-caught individuals with backgrounds of natural variation, the extent of female and male effects on fertility
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