An Ecological Specialization Gradient Does Not Lead to Performance Specialization in Suction-Feeding Guppies

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The way an organism interacts with its environment is the result of multiple systems working together, often in the face of one or more tradeoffs. Therefore, as organisms adapt along environmental gradients, the balance between these system also likely shifts. For example, Trinidadian guppies (Poecilia reticulata) have repeatedly evolved correlated changes in morphology, diet, and behavior along an environmental gradient of predation risk and competition for prey, suggesting a shift in the balance from predator escape to feeding performance, respectively. Much work has demonstrated differences in locomotor morphology, performance, and survival in guppies along this gradient, but demonstration of reciprocal changes in feeding performance have been few. One study suggested that higher feeding rates in the absence of predation were the result of morphological changes in the jaws, indicative of potentially faster movements and stronger suction during prey capture. We tested this hypothesis directly by examining the suction-feeding mechanics of replicate high and low predation pairs of guppies capturing suspended live plankton prey. Our work presents three lines of evidence refuting this hypothesis: there were no differences between populations in induced prey velocity due to suction, suction-feeding kinematics, or capture success rates. Therefore, a tradeoff in suction-feeding is not apparent across a shift in selection gradients in guppies. We propose either that guppies represent a generalist feeding phenotype that does not specialize to habitat, or that performance differences may instead be apparent when guppies capture prey using biting, as this is a more morphologically specialized type of prey capture for these fish.


Society for Integrative and Comparative Biology Annual Meeting (SICB)


San Francisco, CA