It is likely that sex was in their history as within the same genus, there are sexually reproducing whiptail lizards...strange why they gave it up...must have been a lousy dating scene
J Neuroendocrinol. 1995 Jul;7(7):567-76. Related Articles, Links
Species differences in estrogen receptor and progesterone receptor-mRNA expression in the brain of sexual and unisexual whiptail lizards.
Young LJ, Nag PK, Crews D.
Department of Zoology, University of Texas at Austin 78712, USA.
Circulating concentrations of gonadal steroid hormones and reproductive behavior in female vertebrates vary as a function of ovarian state. Steroids secreted by the ovary, specifically estrogen and progesterone, influence the expression of behaviors associated with reproduction by intracellular sex steroid receptors located in specific regions of the brain. Using in situ hybridization, we analyzed estrogen receptor and progesterone receptor messenger RNA expression in several brain regions of ovariectomized, vitellogenic, and postovulatory individuals from two species of whiptail lizards (Cnemidophorus uniparens and C. inornatus). Although these species are genetically very similar, they differ in two aspects of their reproductive biology: (i) the unisexual C. uniparens alternate between expressing female-typical and male-like pseudosexual behaviors while female C. inornatus normally express only female receptive behavior, and (ii) circulating estradiol concentrations in reproductively active female C. uniparens are approximately five-fold lower than in reproductively active female C. inornatus. We found that the regulation of sex steroid receptor gene expression was region specific, with receptor-mRNA expression being increased, unchanged, or decreased during vitellogenesis depending on the area. Furthermore, several species differences in the amount of sex steroid receptor-mRNA were found that may be relevant to the species differences in circulating estrogen concentrations and sexual behavior.