Conspicuous Social Signaling Drives The Evolution Of Chameleon Color Change

What drove the evolution of color change in chameleons?

Chameleons can use
color change to camouflage and to signal to other chameleons, but a new
paper published in the open-access journal PLoS Biology shows that the
need to rapidly signal to other chameleons, and not the need to camouflage
from
predators, has driven the evolution of this characteristic trait.



The research, conducted by Devi Stuart-Fox and Adnan Moussalli, shows that
the dramatic color changes of chameleons are tailored to aggressively
display to conspecific competitors and to seduce potential mates. Because
these signals are quick-chameleons can change color in a matter of
milliseconds-the animal can afford to make it obvious, as the risk that a
predator will notice is limited. This finding means that the evolution of
color change serves to make chameleons more noticeable, the complete
opposite of the camouflage hypothesis. The amount of color change possible
varies
between species, and the authors cleverly capitalise on this in their
experiments.



Stuart-Fox and Moussalli measured color change by setting up chameleon
"duels": sitting two males on a branch opposite each other and measuring
the color variation. By comparing species that can change color
dramatically to those that only change slightly, and considering the
evolutionary
interrelationships of the species, the researchers showed that dramatic
color change is consistently associated with the use of color change as a
social signal to other chameleons. The degree of change is not predicted
by the amount of color variation in the chameleons' habitat, as would be
expected if chameleons had evolved such remarkable color changing
abilities in order to camouflage.

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