Meeting Abstract

73.2  Sunday, Jan. 6  Does community composition affect performance in Rivulus hartii? OUFIERO, Christopher E.*; WALSH, Matthew R.; DO, Tuan; U C, Riverside coufi001@student.ucr.edu

The purpose of this study was to determine the effect of community composition on performance in Hart�s killifish (Rivulus hartii). R. hartii is an egg laying fish that occurs throughout the streams of Trinidad, where much work has been conducted examining evolutionary changes in the guppy (Poecilia reticulata) across sites that differ in predation intensity. Rivulus are also located in the same �high� (HP) and �low� (LP) predation sites as guppies, and are also found in sites by themselves (R). The presence of predators has been shown to cause evolutionary shifts in performance. The general prediction is that HP fish should evolve to maximize their escape abilities, while LP fish should evolve higher endurance to maximize foraging, mating, etc. However, contrasting underlying ecological interactions between the fish communities that lack predators may have differential effects on performance. For instance, the density of Rivulus declines 3-fold in sites with guppies, preliminary evidence suggests that guppies prey upon larval Rivulus, and both species compete for limited resources. Therefore, the predictions for the R and LP sites might not be as easy to disentangle because of these interactions. Using mature, wild-caught, lab-acclimated fish we tested whether the community composition of a species affects its performance. We measured the critical swimming speed (U_crit), sprint speed, and body size of fish from 7 populations (3 R, 3 LP, 1 HP) in 3 river drainages. Preliminary analysis suggests that while there is no significant difference in U_crit between R and LP sites within and among rivers; the HP fish have a significantly lower U_crit than the R and LP sites, consistent with predictions. Additional analyses incorporating body size and sprint speed will be explored. Supported by NSF DDIG IOS-0709788 to T. Garland, Jr. and C.E.O.