Upper Lalaja stream, Trinidad
Experimental Studies of Evolution in
Natural Populations of Trinidadian Guppy
Key Publications can be found in the Publications Tab
The streams draining the rainforests of the Northern Range Mountains have diverse communities of predators downstream and predator free communities upstream, above barrier waterfalls that exclude predators but not guppies. Moreover, these differences in predation risk are repeated in multiple streams, each of which represents an independent instance in which guppies have adapted to life with and without predators. This setting allows comparative studies of guppies to see how the life histories of those who lived with and without predators differed. Early in my career, I used these comparisons to test the predictions of life history theory.
My comparative work led me to discover that evolution by natural selection is a remarkably fast process in guppies. I documented the evolutionary process in just a few years. Guppy evolution can happen in the same time frame as ecological interactions. What are the consequences of evolution being a contemporary, as opposed to historical, process? One answer is that evolution and ecology can interact in ways that can change the outcome of both. To address these interactive dynamics, I am engaged in integrative experimental studies in the natural streams where I began my work on guppies. This work aims to characterize how introduced populations of guppies change their environment, how and how quickly guppies evolve, and how they contribute to shaping their own evolution via their impacts on the ecosystem.
Our ongoing research includes four experimental streams in which we track the pulse of evolution with monthly mark-release-recapture censuses. Our methods allow us to reconstruct the family tree, quantify each individual’s lifetime reproductive success, and quantify the evolution of individual attributes like the life history, morphology, male coloration and all else that changes as guppies adapt to life without predators. Thus far, these experiments have enabled us to characterize eco-evo dynamics as guppies have adapted to their new environment.
In this novel setting, we have begun to address a diversity of important questions on sexual selection and sexual conflict, the evolution of many aspects of the phenotype, species invasions, coevolution and coexistence between guppies and other fish species, the effects of long term climatic trends (e.g., the El Nino cycle or climate change) on population dynamics, and the genetics of adaptation. We often conduct more direct tests of the patterns that we observe in nature in replicate, artificial streams or in the lab.
Guanapo Gorge, Trinidad