Diversity Within The Species

As I continue my quest to complete my book on the lizard species of New Mexico, I periodically find myself in awe of the overall diversity in species that have adapted for life in the varried regions of the state. Recently, I have had the pleasure of close examination and study of the species Holbrookia maculata, the lesser earless lizard. The diversity across this species and across the sexes is impressive. And, I have yet to run across the longer-tailed variety of the extreme southwest corner of the state. (See my previous blog regarding my issues accessing this part of New Mexico.)

Holbrookia maculata ruthveni:
The adaptation of the narrow-ranged ruthveni subspecies to the unique white gypsum sands of Dona Ana and Otero counties of New Mexico through evolution of a bleached out appearance, is an obvious benefit. Combine the extent to which they blend with the substrate and their incredible ability to burrown into the sand in the blink of an eye and you certainly have a lizard poised for success!


White Sands


Subspecies ruthveni Specimen from White Sands


Burrowing under!


Periscope up!

Holbrookia maculata approximans:
Across most of the balance of New Mexico, and especially in the brown Mescalaro Sands, the subspecies is Holbrookia maculata approximans. This subspecies demonstrates dramatic sexual dimorphism. The female is quite vividly colored. Hager¹ provides evidence that changes in coloration of the female are used as an indicator for males of her receptiveness to coppulation. Surely, this benefit must outweigh the negative camoflage aspects of this same coloration.


Subspecies approximans, brightly colored female from the Mescalaro Sands


Same female showing subdued (receptive) coloration


Subspecies approximans, a male from the Mescalaro Sands

References:

1. Hager, S. B. 2001. The role of nuptial coloration in female Holbrookia maculata: evidence for a dual signaling system. Journal of Herpetology 35[4]:624-632.