Collaborative Research: RUI: Transduction of Physiological Stress through Species Interactions: Indirect Effects of Climate Change

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Temperatures on land and in the ocean are rising as a result of increased greenhouse gas concentrations in the atmosphere. Much research to date has focused on the direct physiological influence of rising temperatures on animals. However, an important area that has received less attention is to understand how species interactions will change as a result of warming. This project seeks to characterize the degree to which physiological stresses experienced by one species that is vulnerable to climate change are transduced to a second species through behavioral interactions, even if that second species is not itself vulnerable to climate change. The proposed research will uncover the multifaceted nature of climate change on physiological health, an important problem for all wildlife, including endangered and economically important species. Undergraduate and graduate students will be involved in all aspects of this work, receiving important scientific training. In addition, the researchers are teaming with secondary school teachers to develop educational modules on climate change and ocean life, and school classrooms will be invited to field sites to observe and participate in scientific research. This research will assess physiological and species interaction responses to climate change in a model system for thermal biology: a pair of sympatric intertidal zone porcelain crab species (genus Petrolisthes) that differ in their direct susceptibility to climate change. Both species occur together on rocky Pacific shores but one species lives in the warmer mid-intertidal zone and the other in the cooler low-intertidal and subtidal zones. The mid-intertidal species (the competitive dominant) is more sensitive to rising temperatures than the low-intertidal species (the competitive subordinate) due to the thermal performance of each species and the maximal habitat temperatures they experience. The central hypothesis of the study is that rising temperatures will likely force the mid-intertidal species into the low-intertidal habitat, increasing competitive interactions and causing increased behavioral stress to the low-intertidal species. That hypothesis will be tested in three studies of crabs in the natural habitat, a manipulated field experiment, and a laboratory experiment: (1) Thermal conditions and distributions of crabs will be measured in their natural environments to determine the degree to which warm conditions increase species co-occurrence and the potential for competitive interactions. (2) A manipulative field experiment will be conducted to measure behavioral responses to thermal stress in crabs caged at two intertidal heights. Temperature variation will be regulated by thickness and composition of artificial stones placed over caged crabs, else conditions will vary naturally. (3) Experimental intertidal zone simulation tanks will be used to test for behavioral and physiological responses of each crab species to thermal stress. Heat lamps will be used to regulate temperatures under stones with differing degrees of immersion. In field (2) and laboratory (3) experiments, crab species will be tested separately and in combination. Physiological condition in all three studies will be assessed from hemolymph (blood) samples using existing gene expression thermal stress biomarkers and yolk protein assays of reproductive activity. Gene expression levels of 44 target transcripts and 6 houskeeping genes will be estimated using the NanoString nCounter platform, a non-amplification based direct measurement of mRNA. Assays of yolk protein (vitellin) from oocytes and yolk protein precursor (vitellogenin) from hemolymph will be performed using antibody-based assays (ELISA) with available antibodies.