Changed environmental conditions weaken sexual selection in sticklebacks

Abstract

Environmental heterogeneity can cause the intensity and direction of selection to vary in time and space. Yet, the effects of human‐induced environmental changes on sexual selection and the expression of mating traits of native species are poorly known. Currently, the breeding habitats of the three‐spined sticklebackGasterosteus aculeatus are changing in the Baltic Sea because of eutrophication and increased growth of algae. Here we show that enhanced growth of filamentous algae increases the costs of mating by inducing an increase in the time and energy spent on courtship and mate choice. This is not followed by a concomitant increase in mate attraction, but instead the strength of selection on male red nuptial coloration and courtship activity is relaxed. Thus, the high investment into the costly sexually selected traits is maladaptive under the new conditions, and the mating system mediates a negative effect of the environmental change on the population. We attribute these environmentally induced changes in the benefit of the mating traits and in the strength of sexual selection to reduced visibility in dense vegetation. Anthropogenic disturbances hence affect the selection pressures that mould the species, which could have long‐term effects on the viability and evolution of the populations.

Swingin' in the rain: condition dependence and sexual selection in a capricious world

“…For example, spatial variation in the risk of predation affects both male secondary sexual characters and female preference functions (Stoner & Breden 1988;Houde & Endler 1990). Similarly, sustained temporal change driven by human-induced climate change or pollution affects both signalling and sexual selection ( Järvenpää & Lindström 2004;Møller 2004;Spottiswoode et al 2006;Candolin et al 2007). In addition, the signal can depend more on the early environmental conditions than the underlying genotype (Griffith et al 1999;Qvarnströ m 1999;Jensen et al 2006).…”

Increased temperature disrupts chemical communication in some species but not others: The importance of local adaptation and distribution

“…Previous studies have shown a reduction in the efficacy of sexual signals of many taxa due to human‐induced environmental change (reviewed in Lürling & Scheffer, 2007). For example, massive algae growth related to eutrophication increased the time and energy spent by Gasterosteus aculeatus males in courtship, while at the same time, relaxed the strength of selection in the male red courtship coloration (Candolin, Salesto, & Evers, 2007). Similarly, increased volatility and reduced permanency of scent marks may decrease the information that receivers can gain from chemical signals, reducing their ability to assess male quality (Martín & López, 2012).…”

Dissolved organic carbon and unimodal variation in sexual signal coloration in mosquitofish: a role for light limitation?

“…It is also plausible that the yellow coloration exhibited by fishes inhabiting the most red optical conditions simply reflects lowered investment in signal production. Disruptive transmission environments can relax selection on sexual signal production [46,47]. If the transmission environment is antagonistic to effective signalling, investment in signal production may constitute a substantial fitness cost [48] which could explain the predominance of yellow signals (i.e.…”