On the list of scientific tools that help us understand health, evolution, or the environment, the Trinidadian guppy doesn’t often come to mind.
The fish are seen more as aquarium pets in the US, and in their native Trinidad, wild guppies are so ubiquitous that they’re almost taken for granted.
“In Trinidad, they’re called drain fish, and locals asked us, ‘Why are you studying drain fish?'” said Sarah Fitzpatrick, an assistant professor in Michigan State University’s Department of Integrative Biology.
“Guppies in Trinidad are like squirrels here,” said Sarah Evans, associate professor and peer reviewer of Fitzpatrick at the College of Natural Science.
But thanks to a unique combination of biology and ecology, guppies have been providing researchers with insight into evolution for decades. Evans and Fitzpatrick have taken these findings a step further, demonstrating the potential of guppies to study important questions about how microbes living in host organisms contribute to health, survival and quality of life.
A research team led by the Spartans, both based at the WK Kellogg Biological Station, published their findings May 25 in the journal Proceedings of the Royal Society B.
As scientists learn more about the gut microbiome — the collection of microbes that live in a host organism’s digestive tract — it is becoming increasingly clear that it plays an important role in the well-being of its host. In fact, human health is closely linked to our gut microbiome.
Evans and Fitzpatrick are interested in some of the big questions in biology and wanted to better understand how microbiomes change as organisms evolve.
“Because the microbiome affects fitness — an organism’s health and reproduction — it can affect evolution,” said Evans, a core faculty member of MSU’s Ecology, Evolution, and Behavior program, or EEB.
Nature is full of interesting examples of this, including termites. In their evolutionary path, termites have adapted to welcome populations of unicellular protozoa into their guts, which allow them to digest wood.
Giant pandas are another example. Diet affects a microbiome and pandas only eat leaves. Still, panda microbiomes may be more similar to those of their carnivorous relatives than some of their herbivorous relatives. That’s likely due to the shape and size of the panda’s gut itself, which evolved from a carnivorous ancestor.
Evans and Fitzpatrick wanted to better study what are the biggest drivers of microbiomes as host organisms evolve. It could be things like gut shape, diet, or characteristics of a new environment likely to contain microbes foreign to the host. The researchers knew that guppies could borrow a fin from their unique “natural laboratory.”
“Trinidad is a continental island,” said Fitzpatrick, who is also a core faculty member of the EEB program and coordinator of the Molecular Ecology and Genomics Lab at the Kellogg Biological Station. “It split away from South America a long time ago. It actually has a continuation of the northernmost part of the Andean chain.”
Rivers and streams flow down the mountains of Trinidad in independent systems. Within each water system there are independent ecosystems of guppies, which by nature do not stray far from home.
In the 1950s, evolutionists realized they could take guppies from one ecosystem where the fish had many natural predators and put them in another where they didn’t have any. Over time, the fish’s genes and traits would adapt to reflect native populations in these low-predation environments. Likewise, fish transferred from locations of low predation would adapt when transferred to streams with high numbers of predators.
“And it’s repeatable. They almost always evolve in the same way,” Evans said. “That’s why this system is in the textbooks.”
Materials provided by Michigan State University. Originally written by Matt Davenport. Note: Content can be edited for style and length.