•Natural History of Vertebrates •
| Research Interests |
Comparative locomotor performance in Lampropeltinine snakes The metabolic capacities of an organism can place important constraints on the types of behaviors that are possible or on the frequency and intensity with which a particular behavior can be displayed. For example, locomotor abilities (e.g., maximal sprint speed, stamina) define an "envelope" within which such activities as foraging or searching for mates may occur. In turn, organismal performance abilities are determined by numerous lower-level traits, including aspects of morphology, physiology, and biochemistry. For a comprehensive picture of how behavior evolves it is, therefore, necessary to take an integrative approach that considers variation at multiple levels of biological organization.
Predictors of heart position in snakes The relationship between form and lifestyle or habitat in organisms has frequently been noted by biologists. Such relationships have often been taken as evidence for the adaptive nature of particular morphologies or behaviors. Snakes are remarkably constrained morphologically (save for body size). In essence, all snakes are long tubes and, as such, their musculature and anatomy are modified to fit a tube-like body plan. Additionally, snakes completely lack a pectoral girdle. Absence of the pectoral girdle eliminates a constraint on heart position in snakes. Thus, the heart is relatively free, evolutionarily, to move its anatomical position in the body cavity among taxa. Several studies have attempted to add Gartner, G.E.A., Hicks, J.W., Manzani, P.R., Andrade, D., Abe, A.S., Wang, T., Secor, S.M., and Garland T. Jr., (In Review). Phylogeny, ecology, and heart position in snakes. Physiological and Biochemical Zoology
Is scale variation adaptive to temperature extremes?
Oufiero, C.E., Adolph, S.C., G.E.A. Gartner, T.G. Garland, Jr. 2007. (In Prep). Is variation in scale size and number an adaptive response to climate? A test within the lizard genus Sceloporus. To be submitted to Journal of Evolutionary Biology.
Adaptation in Egg-Eating Snakes (Dasypeltis) A key component to any adaptive hypothesis is that the purported adaptive trait in question must confer a performance advantage (relative to those organisms without the trait) which leads directly to higher Darwinian fitness. Among the most striking hypothesized adaptations in vertebrates are those found in the egg-eating snakes, Dasypeltis. Detailed analyses, dating back 50 years, has highlighted numerous features that appear adaptive to eating exclusively bird eggs, yet no explicit test of egg-eating performance has ever been conducted. We first compared egg-eating performance between Dasypeltis and a facultative egg-eater, Lampropeltis getula. We found that Dasypeltis can eat significantly larger eggs than L. getula. Next, to investigate potential selective pressures (selective regimes) that could lead to the fixation of egg-eating traits, we examined the relative proportions of ground nesting birds in Africa and the United States. There are more birds that lay eggs on the ground, of a readibly ingestible size for Dasypeltis in Africa than in the United States. Natural History of Reptiles I have broad and varied interests in the natural history and conservation of reptiles and amphibians.
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Locomotion is an ecologically relevant measure of integrated organismal function. Furthermore, locomotor behavior is critical in many natural activities, such as escaping from predators. My research aims to first quantify interspecific variation in locomotor performance of snakes, including performances based primarily on either aerobic or anaerobic metabolism. Second, to elucidate mechanisms of proximate causation, the variation in performance will be related to subordinate traits (e.g., heart size, muscle enzyme activities) that are hypothesized to determine performance abilities. Third, performance variation will be related to aspects of behavioral ecology (e.g., habitat use, diet, predatory mode -- obtained from the literature) in order to develop hypotheses about the ultimate (evolutionary) causes of diversity in locomotor behavior. In addition, analyses will consider possible trade-offs between different aspects of locomotor performance (in particular, speed vs. stamina), how these trade-offs are mediated by interactions among the lower-level traits, and whether any trade-offs between performance abilities may relate to (constrain or facilitate) the evolution of behavioral syndromes. 
The Lampropeltinine tribe (Colubridae: king snakes, gopher snakes, etc.) and closely related allies (coach-whips, racers, whip-snakes, etc.) will be studied. These animals are an ecologically and behaviorally diverse group of North American snakes. Their evolutionary relationships are reasonably well resolved, thus allowing application of phylogenetically based statistical analyses. 
ress the question as to why snakes show such a high degree of variation in the placement of the heart within the body cavity. Among the most popular hypotheses is that arboreal snakes have more anteriorly placed hearts to counter the detrimental effects of gravity on blood flow when animals assume vertical postures. While these studies show that arboreal snakes, in general, have more anterior hearts there is considerable overlap among snakes from different habitat types. Further, certain families of snakes (e.g., Viperids) show significant grade shifts (all viperids have more posterior hearts). Our study addresses certain gaps in the previous research. Most notably, advances in snake systematics allow us to use new phylogenetic comparative methods to correct for the non-independence of closely related species. Using an independent data set of 155 primarily South American taxa, we determined what variable (body size, habitat, or phylogeny) best predicted heart position in snakes. We found that in general, phylogeny was a better predictor of heart position than habitat. Thus, heart position in snakes does not seem to show a correlated pattern of phenotype with environment that would be expected from a strictly adaptive mechanism. While habitat can explain a significant amount of the variation in heart position, other causal factors may play an important evolutionary role in determining the placement of the heart in snakes.
genus Sceloporus. Our results show that after controlling for phylogenetic relationships, latitude may be a significant predictor of scale size and number in Sceloporus. Thus, variation in scale number may be an adaptive response to temperature as has been predicted. 