Bilateral Asymmetry in Two Secondary Sexual Characters in the Western Fence Lizard (Sceloporus Occidentalis): Implications for a Correlation with Lateralized Aggression

ABSTRACT\ud BILATERAL ASYMMETRY IN TWO SECONDARY SEXUAL\ud CHARACTERS IN THE WESTERN FENCE LIZARD\ud (SCELOPORUS OCCIDENTALIS): IMPLICATIONS\ud FOR A CORRELATION WITH LATERALIZED\ud AGGRESSION\ud by\ud Jackson D. Shedd\ud Master of Science in Biological Sciences\ud California State University, Chico\ud Spring 2009\ud Three forms of bilateral asymmetry (antisymmetry, fluctuating asymmetry,\ud and directional asymmetry) exhibited by animals have been recognized in the literature.\ud A preference for the use of the left visual field during aggressive intraspecific interactions\ud has been found in a variety of vertebrate taxa. However, correlations between the\ud use of bilaterally asymmetric morphological characters and aggressive displays mediated\ud by neurological asymmetry are not well studied. The western fence lizard (Sceloporus\ud occidentalis) exhibits bilateral asymmetry in two secondary sexual characters\ud used in territoriality; blue abdominal signal patches and femoral pores. Abdominal\ud xiii\ud patches are used in visual communication while femoral pores are used in chemical\ud communication. Here I present data that supports implications for a correlation between\ud visual signaling and left-eye aggression in male S. occidentalis. I measured abdominal\ud patch length and femoral pore number for left and right sides of adult male and female\ud lizards from five localities in northern California. The results from this study show that\ud this species collectively exhibits left directional asymmetry (DA) in abdominal patch\ud length across all field sites. Males also showed left DA in patch length separately from\ud females, which were not found to do so. Further, females collectively expressed a significantly\ud higher number of femoral pores on the left hind limb across all field sites, but\ud males did not. However, both male and female voucher specimens examined from one\ud population, the Sutter Buttes, expressed significant left DA in femoral pore number.CSU, Chic