Meeting Abstract
We study pleiotropic effects of mechanisms underlying pigment production. Melanin, and molecules regulating melanin, can directly and indirectly affect other traits such as aggression and stress physiology. Our earlier study revealed population differences in breeding-season male Sceloporus occidentalis from two elevations. Here we examine four additional populations (two high, two low). As expected, the two new higher-elevation populations were significantly darker than the lower-elevation populations. Principle-components analysis on behavioral responses to staged territorial intrusions revealed that males in the two darker (higher-elevation) populations were more aggressive than males in the two lighter populations, as we found in our earlier two-population comparison. Analyzing baseline plasma testosterone (TESTO) we found no differences associated with elevation and no differences among these four populations. Analyses of plasma corticosterone (CORT) revealed population differences in stress reactivity (CORT after 60-min of captivity) between high and low elevation populations. Hence these high- and low-elevation differences in aggression and stress-reactivity but the lack of an association of behavior with TESTO appear to be robust results. Assays of plasma α-MSH are underway to determine if population differences in the melanization or aggression are associated with differences in plasma levels of this peptide.
