Macroecology of Australian and New World reptiles, with emphases on life history, geographic range, and conservation

This dissertation comprises investigations of numerous aspects of herpetofaunal macroecology, primarily based on analyses of entire continental assemblages of higher herpetofaunal taxa. First, I examine factors determining whether a species is obvious to collectors. For some taxa, species of small body size tend to be described later than large-bodied species. I examine the relationships between body size and date of description for the entire herpetofaunas of North America and Australia. I found that body size is generally a poor predictor of description date. Even within taxa exhibiting a negative relationship between these variables, recently described species could not be distinguished from a random draw from overall species pools. I interpret my results in the light of the history of exploration of these continents and the biology of reptiles and amphibians. Second, I examine life history trade-offs in Australian elapid snakes, which exhibit remarkable plasticity in reproductive traits. I found trade-offs between clutch size and clutch number to be strongly influenced by maternal body size, but the nature of the trade-off differed between oviparous and viviparous taxa. Volumetric or morphological constraints may limit selection on offspring size among oviparous species, while the costs of viviparity may not be especially strong for viviparous species. In general, climatic effects on life history were not pervasive among the entire assemblage of snakes. In Chapter 3, I examined whether ecological characteristics of some species render them especially vulnerable to extinction. I investigated ecological differences between threatened and nonthreatened Australian venomous snakes (Family Elapidae). Correlates of conservation vulnerability identified in previous studies did not discriminate successfully between threatened versus nonthreatened species. However, threatened species tended to rely on ambush foraging; this foraging mode is associated with low rates of feeding, growth, and reproduction. Endangered species typically lacked male-male combat. Next, I analyzed patterns of geographic range size among pitvipers and coral snakes of the New World. Species richness generally peaked in tropical regions, and range size distributions were strongly right-skewed on arithmetic axes. Geographic range size increased with body size in both families. There was little support for Rapoport's Rule except at high northern latitudes. Available continental area had a significant effect on geographic range sizes, while phylogeny had little effect. Finally, I examine the effects of standard museum preservation techniques on body size of snakes. Preserved specimens are often used in studies of life history, but the risks of analytical errors caused by preservative-induced changes in length and mass are poorly quantified. My results indicate that length and mass changes due to preservation are minimal, and I conclude that use of preserved specimens should not bias analyses.