Lizard moms pick larger mates to have sons, smaller for daughters

March 5th, 2010 - 3:24 pm ICT by ANI  

Washington, Mar 5 (ANI): Brown anole lizards are pretty clever when it comes to choosing males to father their kids-they mate with large fathers to produce more sons and go for smaller fathers to produce more daughters, revealed two Dartmouth biologists.

The researchers believe that the lizards do this to ensure that the genes from large fathers are passed on to sons, who stand to benefit from inheriting the genes for large size.

“This species has figured out a clever way to pass on genes with gender-specific effects on fitness. Usually, when natural selection pulls genes in different directions for each gender, the species faces an evolutionary dilemma. But these lizards have solved this puzzle, they’ve figured out how to get the right genes into the right gender,” said Bob Cox, the lead author on the paper.

Researchers manipulated opportunities for females to mate with males of different sizes and found that females prefer larger males.

But, when the choice of partners was limited to small males, females minimized the production of sons.

For researchers, the reason behind this tendency is that the genes that make males more fit are often different from the genes that benefit females, which presents a conundrum because males and females share most of their DNA.

The valuable traits for one gender are not always the same for the other.

“In an evolutionary sense, what’s good for the goose is not always good for the gander,” said Cox.

However, in these lizards, mothers can enhance the fitness of their offspring by manipulating their gender depending on the size of the father.

To demonstrate this, the researchers measured the survival rates of sons and daughters over eight months when released to their natural habitat in The Bahamas.

“As we predicted, the survival of the male offspring increased if they had large fathers. But, we found that the survival of the daughters was not influenced by the size of the father. This suggests that the genetic benefits of large size are specific to sons,” said Calsbeek.

However, the researchers don’t know how do females control the gender of their progeny?

“That’s the big question at this point,” said Cox.

The study is published in the latest issue of Science Express, the advance online publication of the journal Science. (ANI)

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