An Indirect Cue of Predation Risk Counteracts Female Preference for Conspecifics in a Naturally Hybridizing Fish Xiphophorus birchmanni

Pamela M Willis,Gil G Rosenthal,Michael J Ryan,Vincent Laudet

doi:10.1371/journal.pone.0034802

Abstract

Mate choice is context dependent, but the importance of current context to interspecific mating and hybridization is largely unexplored. An important influence on mate choice is predation risk. We investigated how variation in an indirect cue of predation risk, distance to shelter, influences mate choice in the swordtail Xiphophorus birchmanni, a species which sometimes hybridizes with X. malinche in the wild. We conducted mate choice experiments to determine whether females attend to the distance to shelter and whether this cue of predation risk can counteract female preference for conspecifics. Females were sensitive to shelter distance independent of male presence. When conspecific and heterospecific X. malinche males were in equally risky habitats (i.e., equally distant from shelter), females associated primarily with conspecifics, suggesting an innate preference for conspecifics. However, when heterospecific males were in less risky habitat (i.e., closer to shelter) than conspecific males, females no longer exhibited a preference, suggesting that females calibrate their mate choices in response to predation risk. Our findings illustrate the potential for hybridization to arise, not necessarily through reproductive “mistakes”, but as one of many potential outcomes of a context-dependent mate choice strategy.

Highlights

Mate choice is influenced by multiple factors, including mate preference and the current context in which mate choice decisions are made [1,2]
In many species, searching for and choosing among potential mates can conflict with predator avoidance (e.g., [21]), causing individuals to adjust their mate choices to the level of risk [3,4,22]
We have shown that, when conspecific and heterospecific males are distant from shelter, female X. birchmanni prefer conspecifics

Summary

Introduction

Mate choice is influenced by multiple factors, including mate preference and the current context in which mate choice decisions are made [1,2]. Internal and environmental conditions influence the costs and benefits individuals accrue from their choice of mate. Mate choice often varies according to environmental factors such as the level of predation risk [3,4] or the density of potential mates [5,6], and attributes of the choosers themselves such as age, condition, or reproductive state [7,8,9]. Female tungara frogs become less choosy about potential mates as the time remaining for successful reproduction declines [10]. Context-dependent variation in mate choice is important because it may influence evolution by sexual selection; for example, the evolution of novel male traits or the ease of speciation [1,11,12]

Methods

Results

Conclusion