16.2 Wednesday, Jan. 4 Morphological divergence despite gene flow in a Hawaiian waterfall-climbing goby. MOODY, KN*; KAWANO, SM; MAIE, T; BLOB, RW; SCHOENFUSS, HL; BLUM, MJ; PTACEK, MB; Clemson; Clemson; Clemson; Clemson; St. Cloud State; Tulane; Clemson email@example.com
Newly recruiting postlarvae of the Hawaiian waterfall-climbing goby, Sicyopterus stimpsoni, face differential environmental pressures between islands during migration upstream to predator-free breeding habitats. Kaua’i, ~5 MY in age, has long, broad, gradual sloping streams with waterfalls far inland, resulting in long periods of exposure to a non-climbing fish predator placing a premium on adaptations for predator evasion. Hawai’i, ~1 MY in age, has narrow, fast-flowing, steep-sloping streams with waterfalls close to shore, placing a premium on adaptations for waterfall climbing. Our previous work showed that selection favored contrasting body shapes for climbing (streamlined) and predator evasion (tall), potentially promoting local adaptation in shape between island subpopulations. However, the amphidromous life cycle of S. stimpsoni, results in considerable dispersal of oceanic larvae across the archipelago leading to the potential for non-natal recruitment to directly oppose the effects of local natural selection. To examine the interaction between gene flow and local adaptation in shape, we used microsatellite markers and linear morphological measurements to determine the patterns of genotypic and phenotypic differentiation between subpopulations. For adult subpopulations, we found no evidence of between-island or within-island genetic differentiation (FST~0). Morphological differentiation was significant at both levels of island (p<0.0001) and stream-within-island differentiation (both within Hawai’i and Kaua’i p<0.0001). Thus, patterns of morphological differentiation were not congruent with patterns of genetic differentiation at either large or small spatial scales, suggesting an important role for local selection in shaping morphological divergence in the face of high levels of gene flow. NSF IOS-0817794, IOS-0817911.