Meeting Abstract

60.6  Wednesday, Jan. 6  The effect of male group size on female multiple mating and male reproductive success in the golden silk spider RITTSCHOF, C.C.; University of Florida critter@ufl.edu

Across a variety of animal taxa, the outcome of male-male contests depends on size. Winners are larger or have bigger weapons. However, in some cases, large-male advantage changes with density of males. For example, if high male density increases the intensity and frequency of male-male contests, increased male density increases large-male competitive advantage. Conversely, in some cases, at high male densities, defending or guarding females is no longer a successful strategy, and small males who are quicker at finding females copulate more successfully than larger males. In the golden orb spider Nephila clavipes, large males have a competitive advantage in male-male contests. However, male body size and male density are highly variable. In order to test how male density affects large-male advantage, I manipulated male density on female webs and used behavioral observations and molecular paternity analysis to address how density affects the rate of male-male challenges, the body size of successful fathers, and the ability of the mated-male to prevent other males from copulating with the female. I found that large males have a reproductive advantage in higher male density where fighting among males is intense, but small and large males are equally likely to successfully copulate at low male densities where fighting rates are low. Because large-male advantage in N. clavipes is a function of male density, small males could overcome their competitive disadvantage by employing mating strategies that avoid female webs with high numbers of competitors.