invest any energy towards their reproductive or immune systems. Therefore, these females are influenced by resource competition between their reproductive and immune systems. This competition, however, only manifests itself when there are limited resources, and the intensity of this tradeoff depends on the abundance of resources. Since the abundance of resources is malleable because of the constantly changing environment, the intensity of the tradeoff is also malleable. Territoriality Territoriality is an important part of reproduction for many males in this species. Males often defend territories by aggressively excluding other males. This aggression can, in part, be enhanced with higher levels of the steroid hormones testosterone and progesterone. Females have home ranges but they do not defend territories. When the number of females on a male's territory is experimentally reduced by removing the females, the male is more likely to abandon his territory. Phenotype and reproduction Females also can vary in throat coloration, although this is not as well-studied. When gravid with eggs, females tend to be orange or red. Recent experiments also suggest females have association, and perhaps mating preferences for different male types, and that this female preference varies with the throat color of the female herself, and with the colors of the two males that she was presented. Subspecies Ten subspecies are recognized as being valid, including the nominotypical subspecies. U. o. ornatus – Texas tree lizard U. o. caeruleus U. o. chiricahuae U. o. lateralis U. o. levis – smooth tree lizard U. o. linearis – lined tree lizard U. o. schmidti – Big Bend tree lizard U. o. schottii – Schott's tree lizard U. o. symmetricus – Colorado River tree lizard U. o. wrighti – northern tree lizard Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Urosaurus. Etymologies The subspecific name, schmidti, is in honor of American herpetologist Karl P. Schmidt. The subspecific name, schottii, is in honor of German-American naturalist Arthur Carl Victor Schott. The subspecific name, wrighti, is in honor of American herpetologist Albert Hazen Wright. References Further reading Baird SF, Girard C (1852). "Characteristics of some New Reptiles in the Museum of the Smithsonian Institution. Second part". Proc. Acad. Nat. Sci. Philadelphia 6: 125-129. (Uta ornata, new species, p. 126). Behler JL, King FW (1979). The Audubon Society Field Guide to North American Reptiles and Amphibians. New York: Alfred A. Knopf. 743