Allometric Prediction of Locomotor Performance: An Example from Southeast Asian Flying Lizards

Allometric scaling analysis is the standard paradigm for studies attempting to unravel the consequences of evolutionary size change (Huxley 1932; Gould 1966; SchmidtNielsen 1984). Although the value of this approach is clear, prediction of the allometry of performance is often hamstrung by the complexity of biological systems. This complexity derives from the heterogeneous interaction of physiological and morphological variables that together determine maximal performance. Despite this complication, allometric analysis is widely employed primarily because understanding the consequences of size evolution is so important to our field. Not only does size influence virtually every aspect of an organism’s biology (Calder 1984; Schmidt-Nielsen 1984), but it is also remarkably variable, even among closely related species. There is little consensus in the literature regarding the expected relationship between morphology and locomotor performance over a range of sizes. Despite a diversity of alternative models attempting to predict the allometry of performance (Thompson 1917; Hill 1950; Alexander 1968; McMahon 1973, 1975, 1984; Gunther 1975; Bennet-Clark 1977; Rubin and Lanyon 1984; Marsh 1988, 1994; Wakeling et al. 1999), empirical data often fail to conform to any extant model (e.g., Emerson 1978; Garland 1983, 1985; Chappell 1989; Katz and Gosline 1993; Bennett 2000; Wil-