Immediate predation risk alters the relationship between potential and realised selection on male traits in the Trinidad guppyPoecilia reticulata

Abstract

Imminent predation risk affects mating behaviours in prey individuals in a multitude of ways that can theoretically impact the strength of sexual selection, as well as its operation on traits. However, empirical studies of the effects of imminent predation risk on sexual selection dynamics are still scarce. Here we explore how perceived predation affects: (1) the relationship between the opportunity for selection and the actual strength of selection on male traits; and (2) which traits contribute to male fitness and the shape of selection on these traits. We simulate two consecutive reproductive episodes, under control conditions and perceived predation risk using experimental populations of Trinidad guppies. The opportunity for selection is higher under predation risk compared to the control condition, but realised selection on traits remains unaffected. Pre- and postcopulatory traits follow complex patterns of nonlinear selection in both conditions. Differences in selection gradients deviate from predictions based on evolutionary and non-lethal effects of predation, the most notable being strong disruptive selection on courtship rate under predation risk. Our results demonstrate that sexual selection is sensitive to imminent predation risk perception and reinforce the notion that both trait-based and variance-based metrics should be employed for an informative quantification.

Male reproductive phenotype and coercive mating performance in the guppyPoecilia reticulata

“…First, we found that colorful males, with large areas of iridescence and intermediate areas of orange, achieved the highest levels GT (Figure 2). This combination of traits is also associated with reproductive success during cooperative matings in this same guppy population (Devigili et al 2015;Glavaschi et al 2022). Colorful males are expected to be more conspicuous and females should evade their coercive mating attempts more easily, contrary to our result.…”

“…If female choice and male sexual coercion impose different pressures on guppy male phenotypes (Becher and Magurran 2004), we should expect pre-mating traits to be related to our measure of GT performance in opposite ways compared to cooperative mating/reproductive success in this population (Devigili et al 2015, Cattelan et al 2020; Glavaschi et al 2022) and others (Blows et al 2003; Brooks and Endler 2001; Gordon et al 2015). More specifically, body size and male color, which are positively associated with mating success when females are sexually receptive, should be negatively associated with coercive mating success with unreceptive females.…”

“…Here we identified predictors of GT performance in guppies in standard, benign laboratory conditions, but the adoption of this mating behavior in guppies is sensitive to variation in a wide range of environmental factors including: predation risk (Evans et al 2002; Glavaschi et al 2022; Godin 1995), sex ratios (Řežucha and Reichard 2014), population density and sex ratio (Magris et al 2018), light intensity (Chapman et al 2009), food deprivation (Cattelan et al 2020), chemical contaminants (Fursdon et al 2019) and high temperature (Breedveld et al 2023). Therefore, it may be interesting to investigate whether male phenotypes associated with GT performance under different environmental conditions will differ from the ones identified in the present experiment, as is the case for phenotypes favored by females (Cattelan et al 2020; Glavaschi et al 2022).…”

“…Guppy male phenotypes that increase attractiveness and reproductive success in cooperative mating scenarios have been studied in detail. While larger and more colorful males with higher courtship rate are usually preferred by females (Houde 1997), several studies have evidenced that multiple pre- and postcopulatory traits, including body size, gonopodium length, areas of coloration, and courtship rate contribute towards male reproductive success through complex, nonlinear interactions (Blows et al 2003; Brooks and Endler 2001; Cattelan et al 2020; Devigili et al 2015; Glavaschi et al 2022). Sperm reserves and sperm velocity also affect male reproductive success directly in sperm competition (Boschetto et al 2011) and indirectly, through phenotypic (Locatello et al 2006) and genetic correlations with precopulatory traits (Evans 2010).…”

Population‐level food availability affects postcopulatory sexual selection dynamics in the guppy

“…The frequency of polyandry, and hence the relative importance of postcopulatory components in determining male reproductive success can vary extremely among taxa and mating systems (Taylor et al, 2014) and drive the interspecific variation in the expression of male traits associated with mating and fertilization success (Simmons et al, 2017). However, the relative importance of pre‐ and postcopulatory success in determining a male's reproductive fitness can also vary within the same species, not only in association with alternative male phenotypes (Gage et al, 1995) but also as a consequence of the fluctuation of environmental conditions, such as, for example, food availability (Cattelan et al, 2020; Janicke et al, 2015; Winkler & Janicke, 2022), temperature (Gómez‐Llano et al, 2021; Londoño‐Nieto et al, 2023; Moiron et al, 2022; Vasudeva et al, 2014) or predation risk (Glavaschi et al, 2020, 2022). The effect of ecological variation on sexual selection dynamics may vary according to whether the organism is adapted or not to a specific change and may be therefore very specific (Miller & Svensson, 2014).…”