Fig 4.

Evolutionary flux between major trophic resources (top) and rate of trophic evolution (bottom) during the ecological radiation of snakes. Top: Each subpanel illustrates the average number of transitions between a given resource category (e.g., lizards: upper left, yellow) and all resources (numbered circles; see Fig 2); line thickness is proportional to the number of transitions. Reconstructions of ancestral snake diets were inferred using a Dirichlet-multinomial Markov model, and gains and losses between ancestors and descendants were computed under an optimal transport model (see text for details). Colors and numbers follow the same scheme used in Fig 2. Colored lines depict inferred evolutionary gains of different prey categories from the ancestral prey category highlighted in color, and line widths are proportional to the total number of inferred gains. Transitions from only 4 ancestral prey categories are shown. Numerous independent origins of similar feeding strategies occur across the snake tree of life, often from a lizard-eating ancestor. Gains and losses are unequally distributed among prey categories, and some feeding strategies show much greater turnover than others, suggesting that feeding strategies differ in evolutionary accessibility and versatility. Bottom: Reconstructed rates of trophic evolution across 4 major snake radiations indicate that neartic and neotropical (NW) clades exhibit greater net rates of diet evolution than their OW relatives, suggesting that colonization of new biogeographic theaters has been an important source of ecological opportunity in the adaptive radiation of snake diets. In panel (iii), OW relatives include Stichophanes (Dipsadinae) and Pseudoxenodon (Pseudoxenodontinae). Histograms depict the posterior distribution of average clade rates and are derived from evolutionary flux between different trophic resources (see Methods). The data underlying this figure may be found in doi: 10.5281/zenodo.4446064. NW, New World; OW, Old World.