Developmental Cost Theory predicts thermal environment and vulnerability to global warming

Metazoans must develop from zygotes to feeding organisms. In doing so, developing offspring consume up to 60% of the energy provided by their parent. The cost of development depends on two rates: metabolic rate, which determines the rate that energy is used; and developmental rate, which determines the length of the developmental period. Both development and metabolism are highly temperature-dependent such that developmental costs should be sensitive to the local thermal environment. Here we develop, parameterise and test Developmental Cost Theory (DCT), a physiologically explicit theory that reveals that ectotherms have narrow thermal windows in which developmental costs are minimised (Topt). Our DCT-derived estimates of Topt predict the natural thermal environment of 71 species across 7 phyla remarkably well (R2 ~ 0.83). DCT predicts that costs of development are much more sensitive to small changes in temperature than classic measures such as survival. Warming-driven changes to developmental costs are predicted to strongly affect population replenishment, and DCT provides a mechanistic foundation for determining which species are most at risk. DCT predicts tropical aquatic species and most non-nesting terrestrial species are likely to incur the greatest increase in developmental costs from future warming.

Methods
The data are mainly collected from a previous synthesis in Pettersen et al (2019) Ecology Letters.