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

• Main Authors: Kronmarck Claudia, Hennige-Schulz Carmen, Mahlow Kristin, Ziege Madlen, Tiedemann Ralph, Streit Bruno, Plath Martin
• Format: Article
• Language: English
• Published: BMC 2009-08-01
• Series: Frontiers in Zoology
• Online Access: http://www.frontiersinzoology.com/content/6/1/17

<p>Abstract</p> <p>Background</p> <p>Multidirectional interactions in social networks can have a profound effect on mate choice behavior; e.g., <it>Poecilia mexicana </it>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 <it>P. mexicana </it>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^ndpart, 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^ndpart of the tests (specific sperm competition risk treatments).</p> <p>Results</p> <p>The strength of individual male preferences declined slightly also during the control treatment (1). However, this decrease was more than two-fold stronger in audience treatment (2), i.e., with non-specific sperm competition risk including the possibility for visual eavesdropping by the audience male. No audience effect was found in treatments (3) and (5), but a weak effect was also observed when the focal male had seen the previously preferred female sexually interact with a rival male (treatment 4; specific sperm competition risk).</p> <p>Conclusion</p> <p>When comparing the two 'non-specific sperm competition risk' treatments, a very strong effect was found only when the audience male could actually observe the focal male during mate choice [treatment (2)]. This suggests that focal males indeed attempt to conceal their mating preferences so as to prevent surrounding males from copying their mate choice. When there is no potential for eavesdropping [treatment (3)], non-specific specific sperm competition risk seems to play a minor or no role. Our results also show that <it>P. mexicana </it>males tend to share their mating effort more equally among females when the resource value of their previously preferred mate decreases after mating with a rival male (perceived specific sperm competition risk), but this effect is comparatively weak.</p>