The biologically rich Northern Range Mountains on the island of Trinidad are home to a small species of freshwater fish that has made a big name for itself in science. The Trinidadian guppy is famous for its rapid adaptation to changes in the environment. Studying evolution in the wild is difficult, however these fish that adapt to life with or without predators, depending on where they are found in the streams, provide a rare window into evolutionary processes on a short time frame.
Luckily for me, the time frame fits into the span of a PhD dissertation even. Though a long history of guppy research makes these fish an excellent model system for studying evolution in the wild, my work aims to use guppies as a model system for conservation.
A major question for wildlife managers is, “when is it useful to introduce immigrants to rescue a declining population?” This dilemma stems from a historic debate in evolutionary theory in which it is argued that new genetic material can enhance adaptation and ‘rescue’ a small, inbred population or immigrants could bring in disease or genes that do poorly in the new environment and therefore cause the population to crash. This question that I study has rarely been tested empirically, especially in the wild.
Back to Trinidad, underneath the canopy and surrounded by echoing calls of Bell Birds and Channel Billed Toucans, scientists moved guppies from streams with many predators to streams absent of predators. I study the effects on native guppies, who are already adapted to low predation environments, as they receive immigration from the introduced populations of high predation fish.
For two and a half years I visited my focal sites monthly and gave every single guppy a small colored tattoo to recognize individuals. I also took genetic samples and pictures of every guppy so that I can determine if they are native, immigrant, or a hybrid. Combining information about each individual with ultimate patterns of population growth will allow me to understand how immigration from guppies that are adapted to a different environment affects the local populations. This experiment in natural populations will help inform managers make decisions about when to artificially introduce individuals for the sake of conservation.
Beyond experimentation and data collection, through my experiences in Trinidad I’ve gained more than just a lifetime’s worth of mosquito bites, a Trini street dog that now lives with me on the Poudre River, and a bout with tropical fever. Field research is grueling and sometimes imperfect due to the whim of the elements (flash floods, sprained ankles, treefalls) – yet the connections to place, the careful observations, the awareness of subtle change that happens as you become immersed in a field site all contribute to a more nuanced understanding of natural processes. These are the intimate insights we need more of in order to inspire, educate, and conserve.