Meeting Abstract

95.6  Monday, Jan. 6 14:45  Behavioral and hematological changes in relation to melanization in western fence lizard, Sceloporus occidentalis SEDDON, R. J.*; HEWS, D. K.; Indiana State University; Indiana State University rseddon@sycamores.indstate.edu

A growing area of behavioral ecology examines how mechanisms underlying production of animal coloration can affect traits other than body coloration. Melanin, and molecules that regulate melanin, can directly and indirectly affect other phenotypic traits such as aggression or the immune system. Such associations have been studied mainly in birds and mammals, and potential correlates of differences in melanization in reptiles are less well studied. As a first step in examining an elevational gradient in melanization in a lizard, we studied adult males in one high- and one low-elevation population of the western fence lizard, Sceloporus occidentalis. This previously-characterized elevational gradient exhibits increasingly darker-bodied and larger adults at higher elevations. To compare the two populations, we measured agonistic behaviors of males in response to standardized staged territorial intrusions (STIs) during the breeding season (early June 2013, low elevation population; later June 2013, high elevation population) along the Merced River and in Yosemite National Park. We also asked whether there were morphological, hematological, and hormonal differences associated with elevation. Principle-components analysis on behavioral responses to the STIs revealed that darker (higher-elevation) males were more aggressive than males in the lighter population. Males of the darker population had higher mite loads, but did not differ significantly in the white blood cell measures (e.g., heterophil: lymphocyte ratio). We currently are assaying plasma testosterone and corticosterone, and will determine if population differences in the traits examined are associated with difference in plasma levels of these steroid hormones.