Audience effects in the Atlantic molly (Poecilia mexicana)–prudent male mate choice in response to perceived sperm competition risk?

Abstract

Background: Multidirectional interactions in social networks can have a profound effect on mate choice behavior; e.g., Poecilia mexicana males show weaker expression of mating preferences when being observed by a rival. This may be an adaptation to reduce sperm competition risk, which arises because commonly preferred female phenotypes will receive attention also from surrounding males, and/or because other males can copy the focal male's mate choice. Do P. mexicana males indeed respond to perceived sperm competition risk? We gave males a choice between two females and repeated the tests under one of the following conditions: (1) an empty transparent cylinder was presented (control); (2) another ("audience") male inside the cylinder observed the focal male throughout the 2 nd part, or (3) the audience male was presented only before the tests, but could not eavesdrop during the actual choice tests (non-specific sperm competition risk treatments); (4) the focal male could see a rival male interact sexually with the previously preferred, or (5) with the non-preferred female before the 2 nd part of the tests (specific sperm competition risk treatments).

Does Individual Variation in Male Mate Choice Copying Reflect Differences in Social Responsiveness?

“…This score, therefore, represents an equivalent to the copying score described before while being negative instead of positive when focal males changed their preferences. However, to keep our data comparable to previous studies [48,50], we kept those two different designations and formulas.…”

“…We compared association times near either females during the two preference tests and calculated an 'audience score' [48,50] as the difference between the relative association time near the initially preferred female with an audience (2nd preference test) and the relative association time near the same female without an audience (1rst preference test). No change in male association times lead to a score of zero, negative values indicate that the focal males spent less time near the initially preferred female in the 2nd part of a trial and positive values indicate that males spent relatively more time near the initially preferred female.…”

“…We investigated so-called 'audience effects' [43,44] during which males alter their mate choice behavior strategically in response to rival presence [45][46][47]. Poeciliid males, when faced with a rival male during their mate choice (which may observe and later copy their mating decisions) lower their sexual effort and conceal their mate preference, or they even trick their observers by interacting with the previously non-preferred female [32,[48][49][50][51][52][53][54].…”

Male fish use prior knowledge about rivals to adjust their mate choice

“…an audience) when choosing a mate [12,13]. It seems that males respond to the risk of being copied [14][15][16] and thus, cease expressing mating preferences [12,13]. We asked whether males would gather information about rivals when allowed to familiarize themselves with other males.…”

“…We asked whether males would gather information about rivals when allowed to familiarize themselves with other males. Based on the assumption that audience effects are a counterstrategy employed by males to reduce the risk of sperm competition arising from male mate choice copying [12,14], audience effects should occur only when the audience male is either (a) unfamiliar (i.e. its sexual competitiveness is unknown) or (b) familiar, but had been perceived as sexually active and attractive to females.…”