Meeting Abstract

93.4  Thursday, Jan. 7  Non-consumptive effects in a marine food chain with both native and invasive species. GRASON, Emily*; MINER, Benjamin/G; Western Washington University; Western Washington University grasone@students.wwu.edu

Top-down effects by predators are important in structuring marine ecosystems, and predators control prey densities and distributions via consumptive and non-consumptive effects. However, in food chains with invasive species, the magnitude of non-consumptive effects is not yet well studied, and might be different from chains with native species due to different evolutionary histories. In particular, invasive species might not have evolved inducible defenses or offenses to native predators, which should reduce or eliminate non-consumptive effects. We tested whether predator effluent from a native crab altered the avoidance behavior and feeding rates of two invasive oyster drills (the marine whelks Urosalpinx cinerea and Ocinebrina inornata) to determine if non-consumptive effects occur in this system. In both species of drills, individuals increased their avoidance behavior three to five-fold and decreased their feeding rate by 48% – 77% in response to chemical cues from native rock crabs eating conspecific drills. This suggests that rock crabs could help preserve a commercially and ecologically important resource (oysters) through both a consumptive- and non-consumptive trophic cascades. However, the existence of an avoidance response may grant the drills a refuge from predation that prevents the crabs from acting as an effective biotic control. The specificity of the non-consumptive effects was further explored with experiments that attempted to determine what elements of the cue were eliciting a behavioral change. Cue response specificity is particularly relevant in invasive species, as it may help managers predict how novel species will likely incorporate into native communities.