Meeting Abstract
Global change is predicted to increase the physiological stress of many organisms. At the cellular level, nearly all organisms respond to stress by upregulating a highly conserved set of genes in what is known as the cellular stress response (CSR). Though induction of the CSR is typically associated with variation in abiotic stress, there is increasing evidence that stress associated with biotic interactions, such as predation risk and competition, can also induce the CSR. This has many potential implications, including the possibility that biotic and abiotic stress can produce physiologically synergistic negative effects under global change. We investigated species interactions and the CSR using a pair of sympatric, congeneric intertidal crabs: Petrolisthes cinctipes and P. manimaculis. Warming is predicted to cause an increase in the distributional overlap of these species at a microhabitat level. We conducted controlled laboratory experiments in which focal crabs were housed with either conspecifics or heterospecifics. We quantified the number of agonistic interactions focal individuals experienced, and subsequently measured the expression of a number of Heat Shock Proteins (hsps) associated with the CSR. We found that crabs engaged in significantly more agonistic interactions with heterospecifics than with conspecifics; however, there was no difference in hsp expression for crabs with heterospecifics vs. conspecifics. In addition, the number of agonistic interactions an animal experienced did not correlate with hsp expression. This suggests that induction of the CSR may not be a general feature of competitive interactions. Our future work will replicate these experiments under varying density regimes, as we have found evidence that hsp expression is enhanced at high densities in single-species groups.
