Meeting Abstract

P3.47  Wednesday, Jan. 6  Morphological divergence between subpopulations of newly recruited juvenile climbing gobies from different Hawaiian islands: implications for local adaptation MOODY, K.N.; KAWANO, S.M.; PTACEK, M.B.; MAIE, T.; JULIUS, M.L.; SCHOENFUSS, H.L.; BLOB, R.W.*; Clemson Univ.; Clemson Univ.; Clemson Univ.; Clemson Univ. ; St. Cloud Univ.; St. Cloud Univ.; Clemson Univ. rblob@clemson.edu

Variation in selective pressures across the range of a species can generate phenotypic differences between subpopulations, but intermixing of individuals may hinder such divergence via gene flow. The amphidromous lifestyle of the Hawaiian goby fish Sicyopterus stimpsoni provides a system for examining the interaction of these forces. Juveniles returning to freshwater from the ocean face two major pressures: (1) avoiding predators in lower stream reaches, and (2) climbing waterfalls to reach adult habitats. Shapes of adult fish differ between islands where different pressures predominate: adults from Kaua’i have deeper bodies, improving thrust for predator escape in long estuaries on the way to waterfalls, but adults from the Big Island have shallow bodies, reducing drag in waterfalls that are scaled shortly after juveniles enter streams. Because juveniles from different islands may intermix in the ocean, it is possible that fish arriving at each island are morphologically similar, and that the application of different selection regimes across islands to new recruits leads to adult phenotypic divergence. We tested this possibility with discriminant function analysis of 17 morphological measurements from new recruits of S. stimpsoni from Kaua’i (N=80) and the Big Island (N=100). Body height was shallower and anal width was narrower in juveniles from the Big Island vs. Kaua’i, matching adult phenotypes and differences in functional pressures on each island. These results suggest the potential for local entrainment of recruits and possibly sustained selection across generations that could facilitate genetic differentiation between islands. NSF IOS-0817794, 0817911.