Receipt of Seminal Fluid Proteins Causes Reduction of Male Investment in a Simultaneous Hermaphrodite

Nakadera Y, Swart E M, Hoffer J NA, den Boon O, Ellers J, Koene J M. Receipt of Seminal Fluid Proteins Causes Reduction of Male Investment in a Simultaneous Hermaphrodite. Current Biology. 2014;24(8):859-862

Synthesis: Bateman Gradients in Hermaphrodites: An Extended Approach to Quantify Sexual Selection

Sexual selection is often quantified using Bateman gradients, which represent sex-specific regression slopes of reproductive success on mating success and thus describe the expected fitness returns from mating more often. Although the analytical framework for Bateman gradients aimed at covering all sexual systems, empirical studies are biased toward separate-sex organisms, probably because important characteristics of other systems remain incompletely treated. Our synthesis complements the existing Bateman gradient approach with three essential reproductive features of simultaneous hermaphrodites. First, mating in one sex may affect fitness via the opposite sex, for example, through energetic trade-offs. We integrate cross-sex selection effects and show how they help characterizing sexually mutualistic versus antagonistic selection. Second, male and female mating successes may be correlated, complicating the interpretation of Bateman gradients. We show how to quantify the impact of this correlation on sexual selection and propose a principal component analysis on male and female mating success to facilitate interpretation. Third, self-fertilization is accounted for by adding selfed progeny as a separate category of reproductive success to analyses of Bateman gradients. Finally, using a worked example from the snail Biomphalaria glabrata, we illustrate how the extended analytical framework can enhance our understanding of sexual selection in hermaphroditic animals and plants

Receipt of Seminal Fluid Proteins Causes Reduction of Male Investment in a Simultaneous Hermaphrodite

SummaryMating partners often have conflicting interests when copulating [1–3]. One of the major agents affecting female mating partners is seminal fluid, transferred along with sperm. The role of seminal fluid proteins (SFPs) in reproductive success is well studied in separate-sexed animals [4, 5] but is much less so in simultaneous hermaphrodites [6]. The latter potentially have a unique target to exploit for the sperm donor’s own benefit: the male function of their mating partners [7, 8]. Here we show that, in the great pond snail Lymnaea stagnalis, receipt of specific SFPs reduces both sperm transfer and paternity success in a subsequent insemination event. Lowering investment in the mating partner’s male function constitutes a novel role for SFPs. This demonstrates for the first time that hermaphrodites alter their mates’ male as well as female reproductive output [6]. Although it remains to be tested whether this represents mate manipulation or an adaptive response of recipients [9], our findings identify male investment as a new target for postcopulatory sexual selection [10]