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

Abstract

A prominent hypothesis for polyandry says that male–male competitive drivers induce males to coerce already‐mated females to copulate, suggesting that females are more likely to be harassed in the presence of multiple males. This early sociobiological idea of male competitive drive seemed to explain why sperm‐storing females mate multiply. Here, we describe an experiment eliminating all opportunities for male–male behavioral competition, while varying females’ opportunities to mate or not with the same male many times, or with many other males only one time each. We limited each female subject's exposure to no more than one male per day over her entire lifespan starting at the age at which copulations usually commence. We tested a priori predictions about relative lifespan and daily components of RS of female Drosophila melanogaster in experimental social situations producing lifelong virgins, once‐mated females, lifelong monogamous, and lifelong polyandrous females, using a matched‐treatments design. Results included that (1) a single copulation enhanced female survival compared to survival of lifelong virgins, (2) multiple copulations enhanced the number of offspring for both monogamous and polyandrous females, (3) compared to females in lifelong monogamy, polyandrous females paired daily with a novel, age‐matched experienced male produced offspring of enhanced viability, and (4) female survival was unchallenged when monogamous and polyandrous females could re‐mate with age‐ and experienced‐matched males. (5) Polyandrous females daily paired with novel virgin males had significantly reduced lifespans compared to polyandrous females with novel, age‐matched, and experienced males. (6) Polyandrous mating enhanced offspring viability and thereby weakened support for the random mating hypothesis for female multiple mating. Analyzes of nonequivalence of variances revealed opportunities for within‐sex selection among females. Results support the idea that females able to avoid constraints on their behavior from simultaneous exposure to multiple males can affect both RS and survival of females and offspring.

The evolution of sex peptide: sexual conflict, cooperation, and coevolution

“…However, it is not clear that female D. melanogaster experience benefits from polyandry. A number of laboratory‐based studies have failed to detect either direct or indirect benefits (Pitnick, Spicer & Markow, 1997; Brown et al ., 2004; Orteiza et al ., 2005; Priest, Roach & Galloway, 2008; Stewart et al ., 2008; but see Castrezana et al ., 2017 for some evidence of indirect benefits of polyandry in this species). Of course, it is likely that these studies have missed benefits and costs from polyandry that occur in a natural setting; for example, if variance in male quality is higher in natural populations than in the laboratory, then so is the scope for females to benefit from polyandry (e.g.…”

Big data from tiny flies: patterns revealed from over 42,000 phorid flies (Insecta: Diptera: Phoridae) collected over one year in Los Angeles, California, USA

“…Our study is possibly the largest and most complete inventory of an urban fly fauna ever attempted (other similar projects include Avondet et al 2003, Centeno et al 2004, Castrezana et al 2010. Detailed knowledge of a complete fauna allows us to study changes, such as population fluctuations, establishment and spread of invasive species, and extirpation of existing species.…”

Transgenerational effects of multiple mating in Spodoptera litura Fabricius (Lepidoptera: Noctuidae)

“…Multiple mating may benefit females in instances where males transfer resources directly to the females during mating (Castrezana et al, 2017 ), such as replenishing sperm and nutrients in the ejaculate, which may result in an increased number of offspring (Egan et al, 2016 ; Hsu et al, 2014 ; Li et al, 2014 ; Xu et al, 2019 ). In addition, indirect benefits arise from the genetic benefit of increasing offspring genetic diversity (Dunn et al, 2009 ; Egan et al, 2016 ; Johnson & Brockmann, 2013 ; Tregenza & Wedell, 1998 ).…”