PARENT SESSION
Oral Session #12: Aquatic Ecology: Marine.
Presiding: R. Lewison
Monday, August 5. 8:00 AM to 11:30 AM. Mesquite Room, Radisson.

Life at the edge: Examination of the northern geographic range limit of an intertidal snail.

Gilman, Sarah^*,1, ¹ University of California, Davis, Davis, CA

ABSTRACT- For many terrestrial species, the poleward edges of ranges are determined by climate and physiological stress while the equatorward edge is determined by species interactions. There is substantially less evidence for this paradigm among marine specieswhile data on intertidal species hare to sparse to evaluate the pardigm at all. For species with a planktonic (swimming) larval stage, ocean currents could also determine the location of range limits. The intertidal snail Macclintockia scabra is distributed from Mexico to Cape Mendocino, CA. To determine whether the northern range of M. scabra is caused by climate, I conducted a transplant experiment of individuals from two sites within the range to four locations spanning the northern range limit. There was no evidence that snails transplanted beyond the range limit performed worse than control snails transplanted within the range. In contrast, monitoring of larval settlement showed much lower rates of larval settlement into northern populations relative to more central portions of the range. Taken together, these results suggest that factors controlling larval dispersal are responsible for determining the northern range limit of M. scabra, and that physiological tolerance plays a negligible role.

KEY WORDS: geographic range limits, climate, dispersal, Macclintockia scabra