Ecology and Behavior of Lizards of the Parthenogenetic Cnemidophorus laredoensis Complex and Their Gonochoristic Relative Cnemidophorus gularis: Implications for Coexistence

Abstract

The Cnemidophorus laredoensis complex consists of two, all-female parthenogenetic lizard species, designated LAR-A and LAR-B, that commonly coexist with their gonochoristic (= bisexual) relative Cnemidophorus gularis in southern Texas. The ecology and behavior of these Cnemidophorus lizards was studied in a Texas state park where LAR-A, LAR-B, and C. gularis coexist. I used time of capture records to estimate daily activity periods and used focal animal observations of free-ranging individuals to determine what proportion of time lizards spent using different microhabitats, occupying different exposures (full sun, partial sun, shade), and performing different behaviors during the May-June breeding seasons of 1994- 1996. There was little difference among the three species in daily activity period, microhabitat use, or exposure occupancy; added to previously published data on diet similarity, these results suggest that com- petition between the two parthenogens and C. gularis potentially is severe. The greatest behavioral differ- ences were between male C. gularis and female C. gularis, LAR-A, and LAR-B: male C. gularis spent a much greater percentage of their time interacting with other lizards and moved significantly farther per unit time than did females. These results reflect the large proportion of time male C. gularis devoted to trailing and courting female C. gularis as well as parthenogenetic females, especially LAR-A. The only major difference between C. gularis and the two parthenogens was that the latter spent a greater proportion of their time searching for prey. Despite this, LAR-A and LAR-B did not achieve a greater prey capture rate, nor a greater success at locating the preferred prey of termites than did C. gularis, suggesting the two parthenogens are less efficient foragers than their gonochoristic relative. This may account for the reason why the two par- thenogens are not competitively excluding C. gularis from the park despite advantage of a much greater population size. Overall, data from this and other studies lend support to the idea that parthenogenetic Cnemidophorus are ecologically and behaviorally inferior to their gonochoristic congeners and should, therefore, be able to coexist with them only in habitats where selective forces are relaxed.