Species richness in agamid lizards: chance, body size, sexual selection or ecology?
Article first published online: 18 JUN 2003
Journal of Evolutionary Biology
Volume 16, Issue 4, pages 659–669, July 2003
How to Cite
Stuart-Fox, D. and Owens, I. P. F. (2003), Species richness in agamid lizards: chance, body size, sexual selection or ecology?. Journal of Evolutionary Biology, 16: 659–669. doi: 10.1046/j.1420-9101.2003.00573.x
- Issue published online: 18 JUN 2003
- Article first published online: 18 JUN 2003
- Received 2 December 2002; accepted 12 February 2003
- comparative analysis;
- species richness;
- sexual selection
Why does species richness vary so greatly across lineages? Traditionally, variation in species richness has been attributed to deterministic processes, although it is equally plausible that it may result from purely stochastic processes. We show that, based on the best available phylogenetic hypothesis, the pattern of cladogenesis among agamid lizards is not consistent with a random model, with some lineages having more species, and others fewer species, than expected by chance. We then use phylogenetic comparative methods to test six types of deterministic explanation for variation in species richness: body size, life history, sexual selection, ecological generalism, range size and latitude. Of eight variables we tested, only sexual size dimorphism and sexual dichromatism predicted species richness. Increases in species richness are associated with increases in sexual dichromatism but reductions in sexual size dimorphism. Consistent with recent comparative studies, we find no evidence that species richness is associated with small body size or high fecundity. Equally, we find no evidence that species richness covaries with ecological generalism, latitude or range size.