119.4 Tuesday, Jan. 7 11:00 Intraspecific variation in patterns of morphological selection in the waterfall-climbing goby fish, Sicyopterus stimpsoni KAWANO, S.M.*; BRIDGES, W.C.; SCHOENFUSS, H.L.; BLOB, R.W.; Clemson Univ.; Clemson Univ.; St. Cloud State Univ.; Clemson Univ. email@example.com
Selection is the primary driver of adaptive evolution, and local adaptation can occur when selection is stronger than gene flow. The Hawaiian freshwater goby fish, Sicyopterus stimpsoni, exemplifies how the interplay between selection and gene flow can result in population differentiation. The pelagic larval stage during their amphidromous life cycle allows for gene flow across islands, with returning juveniles facing differing selective pressures: 1) escaping from predators in the lower stream reaches, and 2) climbing waterfalls to reach breeding habitats. However, the primary selective agents between Hawai’i and Kaua’i (climbing vs. predation, respectively) may be driving subpopulation differences since adult morphologies match predictions for improving streamlining and thrust production, respectively. We conducted selection analyses to assess whether juveniles recruiting to Hawai'i and Kaua’i exhibit different patterns of morphological selection in response to a brief, yet intense selective agent: waterfall climbing. Our study found that the Hawaiian subpopulation had greater climbing success, and that nonlinear selection patterns were more similar between two Kauaiian subpopulations than between island subpopulations. Quadratic selection was also ~2x stronger on Kaua’i. Traits under selection generally matched predictions for the primary selective agent on each island: taller body heights that could improve predator evasion on Kaua’i, and shallower bodies that improve streamlining during climbing on Hawai’i. These data provide insight into how patterns of morphological selection can contribute to local adaptation despite gene flow.