Meeting Abstract

P3.9  Sunday, Jan. 6  Is more really merrier? A case for increased success under high conspecific densities in the New Zealand mudsnail, Potamopyrgus antipodarum. HANSEN, B.K.*; KRIST, A.C.; MARTINEZ DEL RIO, C.; University of Wyoming; University of Wyoming; University of Wyoming bhanse11@uwyo.edu

Although in its native range Potamopyrgus antipodarum (the New Zealand mudsnail) occurs in populations of sexual and asexual individuals, as an invasive species this snail occurs only as asexual, polyploid females. Asexual P. antipodarum should have a high demand for dietary phosphorus (P) because of high somatic P, high growth rates and increased ploidy. This demand for P may be impacted further by the high population densities that can occur in the invaded range and by the P limitation common in freshwater habitats. Although high densities typically reduce fitness, recent studies suggest P. antipodarum benefits from high densities of conspecifics through increased fecundity. To determine whether conspecific density also affects foraging, we compared preference for high quality food and foraging behavior under increasing densities of conspecifics. Preliminary experiments did not support the hypothesis that P. antipodarum preferred high quality food, but did suggest that feeding activity increased with conspecific density. Consistent with preliminary results, we found no evidence that P. antipodarum preferred high quality food. Previous experiments established that they compensate for low quality food by increasing feeding rate. The probability of P. antipodarum feeding activity increased with conspecific density. Unexpectedly, few P. antipodarum fed in our trials, possibly due to an inability to locate food patches. However, preliminary experiments with an alternate food source suggest that it is more likely that animals found our food unpalatable. Our results may provide insight into the natural history and invasion success of this species.