Meeting Abstract
117.1 Tuesday, Jan. 7 10:15 The dangers of an over-extended phenotype: social and ecological costs of increasing male attractiveness JORDAN, LA; University of Texas, Austin lyndonjordan@utexas.edu
Experimentally testing the costs and benefits of sexual traits is difficult because manipulating one trait often has uncontrolled effects on other traits. Here I use an extended sexual phenotype to measure the cost and benefits of increased male attractiveness in the highly social cichlid fish Neolamprologus multifasciatus using natural experiments at Lake Tanganyika. In this species males uncover shells from the sediment that females use as nest sites, and prior work has shown that shell number directly influences male sexual attractiveness, suggesting that male territories operate as extended phenotypes. Although sexual selection favors males with more shells, I found that territory size in the wild is consistently smaller than in captivity. This is despite the fact that males can easily extend their territory and that shells are an effectively unlimited resource under natural conditions. To examine the paradoxical limitation males place on their own attractiveness, I made experimental additions of increasing numbers of shells to 140 wild groups and measured the social and ecological response. I found that increasing shell numbers caused new females to join, but these were followed by additional males also joining, thereby diluting the potential paternity share of the original male. The most striking cost of the male’s ‘over-extended’ phenotype was that larger piscivorous cichlids usurped many augmented territories entirely, using them as breeding sites and driving off or killing all residents. Even though increasing shell number affords increased access to females, there are strong social and ecological costs of increased attractiveness that are only revealed through experimental manipulation. This study provides a remarkably clear example of classic selection and counter-selection on a sexual trait in the wild.
