Small But Mighty Female Lizards Control Genetic Destiny


“Be faithful in small things because it is in them that your strength lies.” Mother Teresa's words echo throughout the world. They ring particularly true in the biological kingdom among brown anole lizards.

Smallbutmigh Dartmouth researchers Ryan Calsbeek and Bob Cox study male and female brown anole lizards in the Bahamas. As the researchers point out, one of the most striking features of this species is that the males and females actually look like two entirely different species: the males are two to three times larger than the tiny females, weighing just one to two grams apiece. By measuring the lizards' natural and sexual selection, they learned what traits and, by extension, what genes make a high-quality female–i.e. one with high survival and reproductive success. They also learned the traits and genes of a high-quality male are very different from a high-quality female. This is particularly true for body size.

Calsbeek and Cox report their findings in a paper called “Cryptic sex-ratio bias provides indirect genetic benefits despite sexual conflict.”The research is supported by the National Science Foundation's division of Environmental Biology in its Directorate for Biological Sciences. Natural selection favors large males and small females. As lead author Cox puts it, “In an evolutionary sense, what's good for the goose is not always good for the gander.” In other words, a double standard is alive and well.

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