Three Lizards, Three Behaviors

Male side-blotched lizards come in three throat colors--blue, orange, and yellow--and scientists have noticed that each variety displays strikingly different behavior.

The blues form partnerships, the oranges are aggressive, and the yellows are sneaky.

For example, if a pair of blue-throated males are protecting their territory from orange-throated bullies. One blue throat will selflessly step forward to battle the intruder, thereby sacrificing his own chances to successfully mate. As the blues and oranges battle it out, the yellow throats sneak into unprotected territories to find females.

Scientists have long wondered why this altruistic behavior exists since it runs contradictory to an animal's goals of surviving to pass its genes to future generations.

Now Barry Sinervo, of the University of California, Santa Cruz, and colleagues have shown that while altruism may hurt a fighting blue throat's own reproductive chances, it secures the persistence of their genes in future generations by enabling other blue males to mate.

After studying the genomes of males of each throat color, Sinervo determined that at least three other genetic factors other than throat color are at play during the self-sacrificing behavior.

"On the surface, cooperation in the absence of close-relatedness can seem to be evolutionarily counterproductive--but Sinervo explored the genes that underlie cooperative behavior and discovered how they can affect the genetic composition of future generations," said Mark Courtney of the National Science Foundation, which supported Sinervo's research, published in the May 9 Proceedings of the National Academy of Sciences.