Prey Morphology

Much of my work has focused on examining predator-prey interactions in a food web context, but this framework also provides a direct link to other areas of research in ecology and evolutionary biology. For example, in work headed by Brian Langerhans (Washington University), I am studying how prey morphologies may vary across natural and human-altered predation regimes. This work began in Texas, where we demonstrated distinct morphologies in mosquitofish (Gambusia affinis) among predator- and predator-free ponds (see photos). The same general shifts in morphology appear to characterize populations of the Bahamas mosquitofish (Gambusia hubbsi). Freshwater inland blueholes are exceedingly common in the Bahamas, many of which support unique fish assemblages, allowing detailed study of mosquitofish morphology among sites with different suites of predators. In the long-term, we are seeking to link mosquitofish morphology to performance (e.g. burst speed), sexual selection (e.g. morphology-based mate choice), and natural selection (ability to evade predators), providing insights into ecological mechanisms of diversification and speciation.

Human species exploitation and habitat alteration clearly affect assemblage composition and food web structure, but may also drive intra-specific differences among populations. In Venezuelan rivers, commercial netting is becoming increasingly commonplace, and may result in a predation gradient that varies substantially among floodplain lagoons. We are currently investigating whether this human-created predation gradient drives intra-specific morphological differences in prey fishes among lagoons. Similarly, we are examining morphological differences of mosquitofish among blocked and unblocked creeks on Andros Island, Bahamas, as human fragmentation of these systems affects assemblage composition (e.g. fewer piscivores are found in blocked systems) and other environmental gradients (such as flow regime).

One especially interesting finding has been that genital size in mosquitofish may reflect a balance between premating sexual selection (females prefer to mate with males having large gonopodia) and natural selection via predation (males with large gonopodia suffer reduced burst-swimming speed, an important antipredator behavior). More on this line of research can be found on Brian Langerhan’s web site at:

http://biology4.wustl.edu/~lososlab/langerhans/gonop.html

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