Meeting Abstract

P2.48  Sunday, Jan. 5 15:30  Turns out males are picky: no evidence for reproductive interference in an amphipod species complex COTHRAN, RD*; STIFF, AR; CHAMPAN, K; WELLBORN, GA; RELYEA, RA; Univ. of Pittsburgh; Univ. of Pittsburgh; Univ. of Pittsburgh; Univ. of Oklahoma; Univ. of Pittsburgh rdcothran@gmail.com

The co-occurrence of phenotypically similar species at local scales challenges traditional explanations for how communities are structured in nature. This challenge arises because we typically invoke species differences or similarities (e.g., abiotic tolerances, ability to compete for resources or ability to deal with natural enemies) to explain why species do or do not coexist on local scales. However, when species share the same mating biology, reproductive interference (i.e. interspecific mating interactions that are costly for at least one of the species involved) may affect species distributions. Here, we explored the potential for reproductive interference to explain the distribution of cryptic amphipod species that co-occur at local scales in lakes. Through a series of experiments, we discovered that these amphipod species are unlikely to interfere with each other’s reproduction. When not given a choice (i.e. conspecifics were not available as mates), heterospecific mating occurred in 5% of trials. When given a choice, however, heterospecific mating dropped to 0.04%. Surprisingly, detailed behavioral observations revealed that males avoid heterospecifics as mates despite circumstantial evidence that males mate indiscriminately within a species. We discuss these results within the context of a broader research program centered on understanding the distribution of these species and conclude that tradeoffs between competitive ability and predator avoidance likely explain the distribution of these species across microhabitats in lakes.