Environmental Deterioration Compromises Socially Enforced Signals of Male Quality in Three‐Spined Sticklebacks

Abstract

Social costs are often important in promoting the honesty of sexually selected traits. What happens, then, when social costs are relaxed? In species that breed in shallow coastal waters, increases in the frequency and severity of phytoplankton blooms may undermine the value of visual signals by reducing visibility and, in so doing, lead to dishonest signaling by relaxing the social consequences of high signaling effort for poor-quality individuals. Here, we experimentally test the effects of algally induced water turbidity on the role of male-male competition in facilitating reliable sexual displays in three-spined sticklebacks. We found that males in poor condition reduced their courtship effort in the presence of competition in turbid water. This reduction, however, was to a much lesser extent than that observed in clear water. Thus, courtship under conditions of algal turbidity did not reflect male condition as honestly as courtship in clear water. Algal turbidity also influenced breeding coloration, with males in poor condition reducing their area of red nuptial coloration in turbid conditions. Our findings suggest that anthropogenic disturbance to the signaling environment can potentially reduce the evolutionary potential of sexual selection by diminishing the efficacy of visual displays and weakening socially enforced signals of male quality.

Fluctuating mate preferences in a marine fish

“…water temperature and food availability). Furthermore, male sexual signals, and hence female mating decisions, are sometimes influenced by non-stable environmental factors, as has been shown in three-spined sticklebacks (Gasterosteus aculeatus), in which socially enforced signals of male quality are compromised under turbid conditions (Wong et al 2007). Alternatively, as females of some species exhibit individual differences in mate preferences (Brooks & Endler 2001), population-level preferences could fluctuate among years owing to corresponding fluctuations in the abundance of different female types.…”

Does eutrophication-driven evolution change aquatic ecosystems?

“…Dominant males courted more actively and exhibited a larger area of red coloration, which positively influenced female mate choice [22]. Under eutrophication-induced turbidity, social control of the signalling was relaxed and subordinate males were able to vigorously court females and express bright colours, despite the presence of males in better condition [23]. Eutrophication also resulted in a dense mat of filamentous algae around male stickleback nests.…”

Alert signals enhance animal communication in “noisy” environments

“…How animals minimize the effects of environmental degradation on signal propagation is a classic focus of communication research (1)(2)(3) and is often central to understanding the way animals communicate (4)(5)(6) and interact with each other (7)(8)(9). Signal detection theory (10) and empirical studies (3) show that simple signal components suffer lower rates of environmental attenuation than more complex, information-rich components.…”