Fig. 1: Parallel reductions in physiological and life-history traits are associated with viviparity in phrynosomatid lizards.
a Five evolutionary transitions from egg laying (red) to live-bearing (blue) occurred in phrynosomatids. b Viviparous lineages are characterized by reductions in the evolutionary optimal trait values (θ) for cold tolerance (CTmin), field-estimated body temperature (Tb), the laboratory-measured preferred body temperature (Tpref), heat tolerance (CTmax), mass-specific metabolic rate during activity (B), the annual number of offspring (No), and mass-specific production (Pr). Evolutionary optimal trait values were inferred from the Ornstein-Uhlenbeck (OU) model-fitting procedure (see Methods). Each point represents a different stochastic character map from our analyses across the maximum clade credibility tree (n = 500 per trait). These patterns are matched with a strong signal of phenotypic convergence among viviparous species (Supplementary Table 6). Source data are provided as a Source Data file.
