Female guppies’ brains and choice of mates

This video says about itself:

4 October 2014

Sustainable Innovation Initiatives (SII) creates bridges between research, business, industry, tourism and educators to make ecological sustainability a priority for societies in tropical forest ecosystems. Our upcoming documentary series helps us accomplish this goal by reaching many people through video. “Home of the Guppy” is our first episode. It highlights unique features of research in the Northern Range of Trinidad and grassroots efforts in habitats critical to this watershed and communities that use it.

Home of the Guppy Summary:

Streams in Trinidad’s Northern Mountain range have been epicenters for breakthroughs in evolutionary theory over the last five decades. A unique combination of isolation, species-diversity and system-replication has created a “natural laboratory” like no other in the world. These unique conditions have allowed scientists to examine every guppy in multiple wild populations for as many as 15 generations. Guppy studies in Trinidad have produced one of the most detailed multi-generation data collections ever compiled in a wild vertebrate. Results from these studies are reshaping longstanding views of evolutionary theory.

What it means for the world

Features of Trinidad’s stream ecology enable mergers between field and laboratory studies that connect traits such as lifespan, age of maturity and mate-selection, to functions such as cognition and cooperation. Work with Trinidad’s guppies demonstrates the first time that so many traits have been connected with such detail in a wild organism under multiple conditions. Data from Trinidad’s streams has powerful implications for models of evolution and conservation, as well as population management of rare, common and commercially valuable species. Work in Trinidad also vastly updates our understanding of how ecology and evolution are intertwined, and has led to upheavals regarding the time-scales on which the two processes were previously thought to function.

Why are we making this film?

Trinidad’s Northern Range exemplifies how diversity contained in less than 400 square miles of habitat is influencing the world of biology. However it is also valued for land-use, extraction and recreation, as increasing numbers of people utilize the range.

Studying ecology of wild guppies has led to insights affecting applications for biology education, behavioral models, health care and the design of cooperative networks. These applications are assigned high value in the global marketplace.

However, Trinidadians have limited access to globally valued information generated by the biodiversity of their land. This documentary connects local communities and global networks for informed management and value-assignment.

This documentary also raises awareness of how guppy studies are affecting standards of modern biology education. We are working with scientists to make this knowledge accessible at multiple levels of outreach. Our documentary contributes to the type of information access needed for the types of societal functionality that enable sustainable management.

From Science News:

Female guppies with bigger brains pick more attractive guys

But the additional mental power has downsides, too

By Susan Milius

3:54pm, March 22, 2017

When choosing more attractive guys, girl guppies with larger brains have an advantage over their smaller-brained counterparts. But there’s a cost to such brainpower, and that might help explain one of the persistent mysteries of sex appeal, researchers report March 22 in Science Advances.

One sex often shows a strong preference for some trait in the other, whether it’s a longer fish fin or a more elaborate song and dance. Yet after millions of years, there’s still variety in many animals’ color, size, shape or song, says study coauthor Alberto Corral-López, an evolutionary biologist at Stockholm University. Somehow generations of mate choice have failed to make the opposite sex entirely fabulous.

Mate choice could require a certain amount of brainpower, with animals weighing the appeal of suitors and choosing among them. Previous research suggests a smaller brain dims guppies’ mental abilities, and the researchers wondered how brain size might affect the fish’s choice of mate.

To test the idea, researchers used female guppies bred for either a larger or smaller brain. Guppy brains are tiny to begin with, but after five generations of breeding the brain sizes in the study differed by about 13 percent, within the range of what biologists find in the wild.

Each female was offered a choice between a colorful male with orange spots and a bigger tail versus a drab male of about the same weight but without much glory behind. The male fish were installed in compartments at either end of a tank, and females swam back and forth, forced to remember and mentally compare one suitor with his rival.

Females with larger brains showed a preference overall for the more colorful male. Smaller-brained females showed no preference. (The difference did not come from differences in color vision, Corral-López says. The researchers checked the eye genes of the fish and also tested their ability to distinguish colors.)

Interest in flashy-looking males may not be just a fashion choice for females. Orange colors come from pigments in food, suggesting that brighter males may be better fed and healthier, which could lead to healthier offspring. And more colorful males are typically better at finding food. Corral-López also tested females that had not been specially bred for brain size, and these fish preferred the colorful males, too.

But bigger-brained females did not beat their small-brained compatriots in all tests. The smaller-brained guppies tended to grow faster when they were young and to have better immune systems and more offspring.

Thus, circumstances might tip the balance toward or against braininess, the researchers say. Having more babies might be more useful than a discriminating brain, for instance, when food is plentiful and most males manage a decent orange. Such changes in fortune might help explain how variety in appearance persists despite strong mating preferences, Corral-López and colleagues argue. Sometimes flashier males win females, but sometimes drab is just fine.

“Exciting work,” says Molly Cummings of the University of Texas at Austin, who studies fish brains and sexual selection. Checking the fish’s vision was especially important, she says. The results show that females were not “simple slaves to their sensory system.”

The new paper, of course, tracked lab animals, and there’s little data on what differences in brain size mean for mate choice in the wild, says evolutionary biologist Kimberly Hughes of Florida State University in Tallahassee. The new guppy study suggests it’s certainly worth looking at what girl guppies do naturally, she says.

Further Reading

L. Hamers. Brain’s blood appetite grew faster than its size. Science News Online, August 30, 2016.

C. Samoray. Forgetful male voles more likely to wander from mate. Science News Online, December 14, 2015.