Origins of interspecific variation in lizard sprint capacity

1. Data were compiled on maximal sprint speed, body mass and temperature in squamate lizards from the literature and from our own data on lacertid liz ards. 2. Both traditional (i.e. non-phylogenetic) and phylogenetic statistical an alyses showed that sprint speed is positively correlated with body mass ('b igger is better') and temperature ('hotter is better'). 3. Additionally, we tested whether sprint speed correlates with behavioural and ecological characteristics, i.e. foraging mode (sit-and-wait or active ), activity (diurnal or nocturnal), microhabitat use (saxicolous, arboreal or terrestrial) and climate (Mediterranean, xeric, cool or temperate). Liza rds from Mediterranean and xeric climates, diurnal lizards, sit- and wait p redators and terrestrial species are expected to run the fastest. Tradition al tests suggest that lizards from Mediterranean and desert areas are faste r than lizards from cool and tropical regions; that diurnal species are fas ter than nocturnal species; and that saxicolous animals have higher sprint capacities than do arboreal and terrestrial species. No difference was foun d between sit-and-wait predators and actively foraging animals. 4. However, the effects of climate, activity period and microhabitat use we re no longer significant when the data were analysed in a proper phylogenet ic context. This seems to suggest that differences in sprint speed reflect phylogeny, rather than ecology. The discrepancy between the results of phyl ogenetic and traditional analyses forms a strong case for the use of phylog enetic information in comparative studies.