We studied two populations of the mesquite lizard (Sceloporus grammicus), which are both polymorphic for throat color, an important sexual signal. Males in one population exhibit orange, yellow, or blue throats; whereas males in the other exhibit orange, yellow, or white throats. We used mate choice trials to test whether females in each population were better able to discriminate allopatric from sympatric males when the allopatric male was of a morph that did not occur in the female’s home population.
Results/Conclusions
We found that females showed stronger courtship rejection behavior towards allopatric males relative to sympatric males when males in a pair were more different in throat color. Our findings have important implications for the mechanisms by which reproductive isolation may accumulate between populations with polymorphic sexual signals.