Preference for local mates in a recently diverged population of the Lesser Earless Lizard (Holbrookia maculata) at White Sands

When divergent selection favors different phenotypes in different environments, a preference for resident mates can help ensure that offspring are well suited to local conditions, thus increasing an individual's lifetime fitness. Here I use both field and laboratory experiments to investigate the potential for mate choice in a unique color morph of the Common Lesser Earless Lizard, Holbrookia maculata, which inhabits the gypsum dune fields of White Sands in southern New Mexico. I demonstrate that light-colored H. maculata, which have evolved within the last 6,000 years, can discriminate between potential mates. In the field, simultaneous choice experiments revealed that White Sands males in their natural habitat courted females from White Sands sooner than females from a nearby population occupying dark substrate. The use of paint treatments to reverse female dorsal coloration showed that male choice was not based on dorsal coloration alone, if at all. The only variable measured in field trials that correlated strongly with male courtship behavior was female display activity. Resident females displayed in more trials than nonresident females, and males preferentially courted actively displaying females suggesting that behavioral cues may be important in this system. In the lab, sequential choice experiments on an intermediate substrate color showed that preference for local mates was reciprocal, with males of both color morphs preferentially addressing courtship behavior to potential mates from their same locality. By integrating field and lab experiments, I demonstrate that male preference for local mates in the recently diverged White Sands population is robust to experimental design.