Guppies, popular aquarium fish in the US, are ubiquitous in Trinidad. A new study from the Department of Integrative Biology at Michigan State University shows that they may also be important to our understanding of evolution. In Trinidad, they are called plum fish, and the locals have asked us, “Why are you studying plum fish?” says Professor Sarah Fitzpatrick. “Guppies in Trinidad are kind of like squirrels here,” added Professor Sarah Evans.
Trinidad guppies have long been a research model for evolutionary scientists. Now the research team is using the fish to study how microbes in the gut can help the host’s health and quality of life. It’s not just about guppies: previous research shows that our own health is directly related to the microbes that live in our gut.
Because the microbiome influences fitness – the health and reproduction of an organism – it can influence evolution,” says Prof. Evans, who is principal lecturer in the Ecology, Evolution, and Behavior program at MSU.
Some organisms, such as termites or pandas, actually depend on microbes in their guts to digest food, such as wood or leaves, without which they would not be able to live. These factors may include the shape of the intestines, diet, or environmental factors.
Guppies in Trinidad are often unique to individual streams, never leaving their little pond for their entire lives. Because of this, guppy’s unique ecosystems are easy to find, making it much easier to study evolution.
“Trinidad is a continental island,” says Professor Fitzpatrick. “It separated from South America a very long time ago. It actually contains an extension of the northernmost part of the Andes mountain range.”
Decades ago, in the 1950s, evolutionary researchers experimentally moved guppies from an area with many natural predators to an ecosystem with few predators. Over time, new guppies changed and became more like local guppies, the same thing happened in the opposite direction.
“And it repeats itself. They evolve in much the same way almost every time,” Prof Evans says. “That’s why this system has entered the textbooks. As we unravel the complexities of the evolution of the host microbiome in the wild, research must take into account microbial colonization of the environment, host phenotypic plasticity in nature, and more realistic environmental conditions excluded from laboratory studies.”
The study was published in Proceedings of the Royal Society B.