Meeting Abstract
Intraguild predation (IGP), where two consumer species compete for a shared resource and also prey upon each other, commonly occurs in nature, but ecological theory suggests that this complex interaction can only persist under a relatively narrow range of conditions. A variety of behavioral mechanisms can facilitate the coexistence of intraguild predators, including temporal or spatial specialization. The IGP interactions of Trinidadian killifish (Rivulus hartii) and Trinidadian guppies (Poecilia reticulata) in the headwater streams of the Northern Range Mountains of Trinidad present an opportunity to test these mechanisms in nature. We experimentally introduced guppies into 4 previously guppy-free, killifish only streams in 2008-2009 to simulate the natural colonization of killifish-only habitat by guppies. We paired experimental introduction reaches with reaches located upstream above barrier waterfalls that provided a killifish-only control. Each stream habitat is naturally divided into pools and riffles. Guppies are diurnal and tend to specialize in pool habitats, so we assessed the hypotheses that killifish would become more nocturnal and lay more eggs in riffle habitats in introduction sites relative to controls to minimize IGP interactions with guppies. We found that killifish significantly changed their diel activity patterns to become more nocturnal in one stream (χ23=17.8, p<0.001). Similarly, introduction killifish laid significantly more eggs in riffles than pools, while control killifish favored pools over riffles for egg laying across all 4 streams (χ21=7.0, p=0.008). Thus, behavioral adjustment of diel patterns and habitat use may reduce antagonistic IGP interactions between guppies and killifish and facilitate coexistence.
