The Panamanian slender anole (Anolis apletophallus).

In keeping with the previous year, Albert Chung (now a Ph.D. student at UCLA with Shane Campbell-Staton), presented in the prestigious Division of Ecology and Evolution Raymond B. Huey best student paper session of SICB2020. Albert’s work encompasses a very old, enduring, and important question in biology: how males and females of the same species exhibit differences in so many traits, despite the fact that males and females share a common genome.

A male brown anole from the island of Great Exuma, in The Bahamas.

This dynamic is called sexual conflict: when what is best for one sex might not be the best for the other sex, and has challenged biologists for decades to study a multitude of incredible organisms to answer this question, including anoles! Albert and his collaborators addressed this question by studying two species of anole, the brown anole (Anolis sagrei) and the Panamanian slender anole (Anolis apletophallus). Brown anoles are one species where males are super large compared to females, whereas in the slender anole, males and females are relatively the same size.

Albert et al. described differences in the genes expressed in both males and females to understand what factors promote the development of male-biased size dimorphism. They found that differences in gene expression between males and females was highest in gonad tissue compared to liver and brain tissue, and that when female lizards are supplemented with additional testosterone (traditionally viewed as a hormone more highly concentrated in males of a given species), their gene expression profiles look like those of male lizards. They also found that liver tissue exhibits the greatest differences in sex-biased gene expression, because the liver is one organ responsible for supplying the body with the energy and molecules needed for growth. They suggest that differences in gene expression between males and females might be one factor promoting the evolution of size differences between the sexes, and that physiological controls on these genes could play prominent roles in having males and females exhibit huge differences in traits despite sharing a similar genetic makeup.

 

Anthony Gilbert
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