Animals make more complex decisions about choosing mates than earlier thought

June 9th, 2009 - 1:30 pm ICT by ANI  

Washington, June 9 (ANI): Purdue University researchers have shown that animals make more complex decisions about choosing mates than earlier thought.

Andrew DeWoody, who led the study published in the journal Molecular Ecology, says that it is not just major histocompatibility complex (MHC) genes that animals use as the sole basis for mate choice.

“Our data indicate that mate-choice decisions aren’t solely dependent on MHC, tail length, body size or any other single factor. Mate choice is a complex process that takes many factors into account,” said DeWoody, a professor of genetics.

Working in collaboration with former postdoctoral assistant David Bos, who is presently a continuing lecturer at Purdue, DeWoody set out to see how much MHC genes affected mate choice in wild animals.

Most prior research showed that an animal would choose a mate with MHC that is the most divergent from its own so that offspring will have more effective immune systems.

Earlier studies in mice suggest that MHC diversity was the sole genetic basis for mate choice.

However, DeWoody contends that those studies used mice that were genetically the same in every way except for MHC.

“Sure, mice might base mate-choice decisions wholly on MHC if there is no other consideration, if they don’t have any other factors to choose from. But wild animals have a lot of different characteristics they can choose from, not just MHC,” DeWoody said.

The researchers used tiger salamanders for their study because of their unique mating habits in which females make the sole decision on choosing a mate.

Males deposit spermatophores, or sperm packets, for females, who choose the ones that will be used to fertilize their eggs.

DeWoody said that the females are choosy because they want a mate whose attributes will increase the fitness of their offspring.

During the study, the researchers gave each female a choice between two males, and checked the offsprings’ genotypes to identify parentage.

They found that the largest females chose the more MHC-similar mates, not the most divergent ones as expected under prevailing theory. The remaining females seemed to mate at random with regard to MHC.

The research team said that apart from MHC, tail length plays a role in reproductive success, for male salamanders with longer tails were found to be twice as likely as those with shorter tails to be chosen as sires.

Bos said that it was possible that other factors outweighed MHC for some of the females.

“There may very well be trade-offs. Getting a mate with diverse MHC, large body size and other characteristics might be nice, but getting all of those characteristics might not be practical,” Bos said.

Both DeWoody and Bos would like to conduct similar tests on other MHC genes or on animals in more complex environments.

Bos said that understanding the factors used to determine mate choice could lead to better understanding of mating habits in all animals, including humans. (ANI)

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