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Waterfall climbing fishes of Hawai'i

Functional selection and population divergence

In many species of gobiid fishes native to island streams, juveniles are flushed to the ocean after hatching and must climb massive waterfalls (up to 10,000x body length) to return to adult habitats.  Before reaching waterfalls these fish must swim through gauntlets of predators. My lab is collaborating with Heiko Schoenfuss and Matt Julius (St. Cloud State) and Margaret Ptacek (Clemson) on studies of biomechanics, ecology, and population genetics that examine how these remarkable fishes survive such extreme demands, focusing on species from the Hawaiian Islands. 

Functional studies have examined waterfall-climbing mechanics in goby juveniles and adults (Schoenfuss and Blob 2003, 2007; Blob et al. 2006, 2007); recolonization of volcanically disturbed streams (Schoenfuss et al. 2004); goby feeding mechanics and performance (Maie et al. 2009a, 2009b, 2014; Cullen et al. 2013); and differences in the performance of goby suckers (Maie et al. 2007; Maie et al. 2012, 2013) and muscle fiber types (Cediel et al. 2008; Maie et al. 2011) across species. We have extended this work to evaluate morphological and genetic divergence between populations across the archipelago (Hawai’i vs. Kaua’i) subject to different levels of selection for climbing performance versus evasion of predators (Schoenfuss et al. 2013; Moody et al. 2015).  We found significant morphological divergence between juveniles from these islands that met our predictions based on the primary pressure each presents: streamlined bodies to improve climbing on younger Hawai’i, where waterfalls are close to shore, versus taller bodies to aid thrust production for predator escape on older Kaua’i, where most falls have eroded further inland (Blob et al. 2008, 2009, 2010).  We have also conducted laboratory selection experiments for both climbing performance and predator evasion, providing evidence that these pressures generated observed patterns of morphological divergence through the tradeoff between their competing demands (Blob et al. 2008, 2009, 2010). 

This material is based upon work supported by the National Science Foundation under Grant No. 0817794.  Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author and do not necessarily reflect the views of the National Science Foundation.