Meeting Abstract

44.9  Saturday, Jan. 5  Endurance and physiology in Urosaurus ornatus: sex and morph differences? FOULKES, EC*; THAKER, M; HEWS, DK; Indiana State Univ. efoulkes@indstate.edu

Locomotory performance has been the focus of many ecological and evolutionary studies, and lizards have been a model system. Less work has examined intraspecific variation in performance and suites of underlying physiological traits, especially in a species with alternative reproductive tactics that show variation in spatial use patterns. To assess the functional ecology of movement behaviors of male morphs and of females, we examine variation in endurance, and in plasma metabolites, plasma steroid hormones, and muscle fiber types in wild ornate tree lizards (Urosaurus ornatus). In our study population, males having orange throats with a central blue patch (OB males) are territorial, and those with solid orange throats (O males) are non-territorial rovers or satellites. We also studied a third morph, mottled, which behaves similarly to OB males in antipredator contexts (territorial behaviors are uncharacterized). We tested the hypothesis that morph differences in space use are reflected in endurance and in key physiological traits. To estimate endurance, lizards were run on a treadmill immediately after capture. The trial ended when the lizard was exhausted and no longer moved forward in response to gentle prodding on the tail base. Immediately after the trial, we obtained a blood sample and either sacrificed the lizard for further histological study or released it. We did not find significant sex or morph effects for endurance. For all males, lighter males ran significantly longer than heavier males. Within the OB morph, there was a trend for males with lower initial body temperatures to run longer. To assess physiological correlations with endurance, we are measuring levels of testosterone, corticosterone and plasma metabolites, and determining muscle fiber-type proportions in a key thigh muscle.