Sexual cannibalism and population viability.

Adam M Fisher,Gregory I Holwell,Stephen J Cornell,Tom A R Price

doi:10.1002/ece3.4155

Adam M Fisher, Gregory I Holwell + Show 2 more

Open Access

https://doi.org/10.1002/ece3.4155

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Abstract

Some behaviours that typically increase fitness at the individual level may reduce population persistence, particularly in the face of environmental changes. Sexual cannibalism is an extreme mating behaviour which typically involves a male being devoured by the female immediately before, during or after copulation, and is widespread amongst predatory invertebrates. Although the individual‐level effects of sexual cannibalism are reasonably well understood, very little is known about the population‐level effects. We constructed both a mathematical model and an individual‐based model to predict how sexual cannibalism might affect population growth rate and extinction risk. We found that in the absence of any cannibalism‐derived fecundity benefit, sexual cannibalism is always detrimental to population growth rate and leads to a higher population extinction risk. Increasing the fecundity benefits of sexual cannibalism leads to a consistently higher population growth rate and likely a lower extinction risk. However, even if cannibalism‐derived fecundity benefits are large, very high rates of sexual cannibalism (>70%) can still drive the population to negative growth and potential extinction. Pre‐copulatory cannibalism was particularly damaging for population growth rates and was the main predictor of growth declining below the replacement rate. Surprisingly, post‐copulatory cannibalism had a largely positive effect on population growth rate when fecundity benefits were present. This study is the first to formally estimate the population‐level effects of sexual cannibalism. We highlight the detrimental effect sexual cannibalism may have on population viability if (1) cannibalism rates become high, and/or (2) cannibalism‐derived fecundity benefits become low. Decreased food availability could plausibly both increase the frequency of cannibalism, and reduce the fecundity benefit of cannibalism, suggesting that sexual cannibalism may increase the risk of population collapse in the face of environmental change.

Highlights

Sexual cannibalism typically involves a female devouring a conspecific male immediately before, during or immediately after copulation
There are three main hypotheses that suggest why sexual cannibalism is maintained in nature: (1) adaptive foraging—females devour males in order to gain essential nutrients and are more likely to do so when starved (Barry, Holwell, & Herberstein, 2008; Hurd et al, 1994; Roggenbuck, Pekár, & Schneider, 2011); (2) mate choice—sexual cannibalism represents an extreme form of mate choice in which non-preferred males are devoured to prevent copulation (Elgar, Schneider, & Herberstein, 2000; Hebets, 2003; Persons & Uetz, 2005; for a review see: Prenter, MacNeil, & Elwood, 2006); (3) aggressive spillover—adult female aggression towards conspecific males is a by-product of strong selection for juvenile aggression (Arnqvist, 1992; Henriksson, 1997; Johnson & Sih, 2005)
We have demonstrated that sexual cannibalism can have both positive and negative impacts on population growth rate

Summary

| INTRODUCTION

Sexual cannibalism typically involves a female devouring a conspecific male immediately before, during or immediately after copulation. Female diet can create large variation in sexual cannibalism rates within species; female Pseudomantis albofimbriata (false garden mantis) cannibalise males at an average of 89% of encounters when starved, compared to 0% of encounters when satiated (Barry et al, 2008). In the case of pre-copulatory cannibalism, an adult male is removed from the population and both the male and the female miss out on copulation and the fertilisation of the female’s eggs. Both of these effects of sexual cannibalism are likely to increase the proportion of adults in the population, both male and female, that die as virgins. We compare the population-level effects of pre-and post-copulatory cannibalism separately to give a more holistic overview of how sexual cannibalism can impact on species ecology

| METHODS

| DISCUSSION

Findings

CONFLICT OF INTEREST