Meeting Abstract

P2.111  Monday, Jan. 5  Comparative Morphological Selection: Waterfall-climbing in Gobiid Fishes from Dominica versus Hawai'i KAWANO, S.M.*; SCHOENFUSS, H.L.; MAIE, T.; BRIDGES, W.C.; BLOB, R.W.; Clemson University; St. Cloud State University; Clemson University; Clemson University; Clemson University

When closely related species are exposed to similar selection pressures, will they respond in similar ways? To investigate this question, we subjected juveniles of the amphidromous gobiid fish Sicydium punctatum from the Caribbean island of Dominica to climbing trials up an artificial waterfall (~100 body lengths) to evaluate body shape differences between successful and unsuccessful climbers, and then compared our results to those of previous studies on the closely related species Sicyopterus stimpsoni from Hawaii (Big Island). Failure rates were greater in fish from Dominica (>50%) than in fish from Hawaii (~30%). However, selection did not yield the same patterns between the two species. Although numerous morphological differences were found to be significant between successful and unsuccessful climbers in S. stimpsoni from Hawaii, calculations of selection differentials and gradients showed very few significant patterns of directional selection on morphology induced by climbing in S. punctatum from Dominica. The differing responses of Hawaiian and Dominican gobiids may be related to differences in the selective pressures that have acted on these species through their evolutionary history. For example, while the waterfalls scaled by Dominican gobiids are typically less severe than those scaled by gobiids on the Big Island, Dominican gobiids are exposed to in-stream predators that are absent above waterfalls on Hawaii. Our findings suggest that selection need not operate in a uniform manner amongst closely related groups, and that several factors might act to counter expected effects of natural selection on specific aspects of performance. Supported by NSF (IOS-0817794, IOS-0817911).