Data and code from: Live birth in lizards: A process-based model for the roles of temperature, behavior, and life-history

Life-history traits evolve to optimize fitness trade-offs across an
organism’s life cycle. Potentially to mediate the trade-off between
survival and fecundity, multiple animal groups have independently evolved
live birth (viviparity), including at least 70 transitions in lizards
alone. In lizards, viviparity is thought to evolve as a mechanism to
improve embryonic development in cold climates (cold climate hypothesis,
or CCH), possibly at the expense of the mother’s survival. Past
comparative studies often align with the CCH’s predictions, but they
usually treat core features of the hypothesis as implicit and, most
importantly, infer process from pattern rather than testing causal
mechanisms. To address this, we developed a process-based model that
integrates behavior, thermal physiology, life history, and climate to
predict optimal gestation length in lizards globally. We generated a
comprehensive trait database of 89 lizard populations that vary in parity
mode, and we used ecophysiological modelling to test our model’s
predictive power. Our model produced accurate predictions, strongly
supporting the hypothesis that cold climates favor the evolution of
viviparity in lizards and revealing the ecological contexts and underlying
mechanisms by which this life history strategy evolves.