Temperature-mediated coexistence in temperate forest ant communities

Patterns of ant species diversity are well documented and yet the mechanisms promoting species coexistence among communities are often elusive. Two emerging hypotheses that account for coexistence in ant communities are the discovery-dominance tradeoff and the dominance-thermal tolerance tradeoff. Here we used behavioral assays and community-level sampling from ant assemblages in the southern Appalachians, USA to test for the discovery-dominance and dominance-thermal tolerance tradeoffs. Species that were behaviorally dominant during interspecific interactions tended to forage in a narrow window of generally warmer temperatures, whereas subordinate species tended to forage in a wide range of temperatures, including colder temperatures. Species that foraged at lower temperature tended to be behaviorally subordinate, suggesting that a dominance-thermal tolerance tradeoff promotes coexistence in this system. Species richness was positively related to site average annual temperature and within-site variation in ground temperature, suggesting that temperature also shapes the structure of ant communities and regulates diversity. There was no relationship between the ability of a species to discover food resources and its behavioral dominance, contrary to the predictions of the discovery-dominance tradeoff hypothesis. In sum, our results show that temperature plays numerous roles in promoting regional coexistence in this system.*[In total, we detected 17 species along the elevational gradient at Coweeta LTER. Based on pitfall trap catches, the most abundant species were A. rudis (83%), P. imparis (16%), & Myrmica punctiventris Roger (15%). We recorded a total of 15 species in pitfall traps, but only 9 of these species were also recorded at baits. Only 2 species, Aphaenogaster rudis Enzmann & Prenolepis imparis Emery (1893) were observed foraging at night.]