Meeting Abstract
Male Sceloporus lizards mediate social interactions through multimodal signals involving chemical secretions and visual displays of motion and color. Several independent evolutionary losses of a key visual signaling trait (blue abdominal patches) have occurred in Sceloporus, and previous studies suggest species that have lost the visual signal may use chemical information more than do species with the coloration. In response to elevated androgens, femoral glands (FGs) of breeding season males exude waxy secretions containing volatile organic compounds (VOCs), lipids and proteins. We predicted loss of the blue signal would be associated with increases in the relative proportion of some VOCs, and exogenous androgens would also increase relative proportions of some VOCs. We analyzed VOC components of FG secretions from four Sceloporus spp. (2 blue, 2 white) with gas chromatography-mass spectrometry. We tentatively identified 25 compounds including linear carboxylic acids and methyl ketones. The abundance of carboxylic acids varied among species but showed no distinct pattern associated with abdominal patch color. The abundance of methyl ketones was higher for one white species relative to the more closely related blue species, however, the opposite pattern was observed in the other species pair. Finally, exogenous testosterone implants in males of a blue species, S. occidentalis, increased production of FG secretions as is commonly found, but also increased the relative proportions of some steroid compounds.
