Guppies are helping us understand evolution

Guppies, the popular aquarium fish in the US, are ubiquitous in Trinidad. New research from Michigan State University’s Department of Integrative Biology shows they may also be important to our understanding of evolution.

“In Trinidad, they’re called drain fish and locals would ask us, ‘Why are you studying drain fish?’” said Professor Sarah Fitzpatrick. “Guppies in Trinidad are kind of like squirrels here,” added Professor Sarah Evans.

Trinidadian guppies have long been a research model for scientists looking at evolutionary questions. Now, the research team is using the fish to study how microbes in the gut can help a host’s health and quality of life. It’s not just guppies either, previous research shows that our own health is directly connected to the microbes living in our gut.  

“Because the microbiome affects fitness – an organism’s health and reproduction – it can affect evolution,” said Professor Evans, who is a core faculty member of MSU’s Ecology, Evolution and Behavior Program.

Some organisms like termites or pandas actually depend on microbes in their guts to digest their food like wood or leaves – without which, they wouldn’t be able to live. The Michigan State researchers wanted to understand what factors drive certain microbes to take up residence. These factors may include gut shape, diet or environmental characteristics. 

Guppies in Trinidad are often unique to individual streams, not leaving their little water course for their entire lives. Due to this, unique guppy ecosystems are easy to find and make studying evolution quite easy. 

“Trinidad is a continental island,” said Professor Fitzpatrick. “It split off from South America a long time ago. It actually has a continuation of the northernmost part of the Andes mountain range.” 

Decades back in the 1950s, evolution researchers experimentally transferred guppies from an area with lots of natural predators to an ecosystem with few predators. Over time, the new guppies would change to be more similar to the native guppies, and the same works in reverse as well. 

“And it’s repeatable. They evolve in many of the same ways almost every time,” said Professor Evans. “That’s why this system is in textbooks.”

“As we unravel the complexities of host–microbiome evolution in the wild, studies should consider environmental microbial colonization, host phenotypic plasticity in nature, and more realistic environmental conditions excluded from laboratory studies,” wrote the researchers.

The research is published in the journal Proceedings of the Royal Society B.

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By Zach Fitzner, Earth.com Staff Writer