A male Trinidadian guppy, Poecilia reticulata
Some questions are too big to answer with larger fish we've studied, so we turned to a very small fish that can be housed and manipulated in the lab more easily. I was first introduced to guppies, and how they have helped us learn about evolution, by David Reznick when I was at the University of California, Riverside. Sparked by our interactions, I applied for and received a NSF Postdoctoral Fellowship in Biology to work with Cameron Ghalambor to use guppies to start to understand how integration of feeding and swimming is involved in patterns of evolutionary change in organisms.
Trinidadian guppies (Poecilia reticulata) live in freshwater streams and rivers throughout the Caribbean and South America. Their location on the island of Trinidad is unique because they have repeatedly colonized upstream reaches of streams where major predators can't survive. Other differences between these habitats include decreased productivity and prey availability as well as increased population density and competition in new upstream environments. Because of these changes, guppies evolve differences from their downstream counterparts in body size and shape, male color patterns, life history, behaviors, and many more traits. This has happened over and over again, independently in each river, making guppies a natural evolutionary experiment that can be used to test questions about how animals adapt to new environments.
A schematic showing the differences in environments between guppy populations above and below waterfall barriers in Trinidad
We're interested in how this natural variation in the environment results in changes in swimming and feeding traits, and how these changes influence the ability to coordinate swimming and feeding during prey capture. So far, we've primarily described natural variation in feeding and integration with locomotion within and across wild populations. For example, we showed that female guppies repeatedly evolve an integrated relationship in more recently colonized low predation habitats, but this relationship is absent in high predation habitats (see the paper here). This pattern suggests that as guppies evolve to their new upstream habitats, they also evolve integration.
Work in the lab continues to build on these ideas using using guppies and other closely related fishes to further understand several main questions:
How does selection from the environment act on integration, and can we replicate these processes in the lab?
What do patterns of integration and environmental variability look like in other species? Can we identify broad patterns or "rules" to explain this complexity?
Check out some highlights from our collection trip to Trinidad in March 2017 as well as the work we've been doing since then.: