Rapid increase in snake dietary diversity and complexity following the end-Cretaceous mass extinction

Abstract

The Cenozoic marked a period of dramatic ecological opportunity in Earth history due to the extinction of non-avian dinosaurs as well as to long-term physiographic changes that created new biogeographic theaters and new habitats. Snakes underwent massive ecological diversification during this period, repeatedly evolving novel dietary adaptations and prey preferences. The evolutionary tempo and mode of these trophic ecological changes remain virtually unknown, especially compared with co-radiating lineages of birds and mammals that are simultaneously predators and prey of snakes. Here, we assemble a dataset on snake diets (34,060 observations on the diets of 882 species) to investigate the history and dynamics of the multidimensional trophic niche during the global radiation of snakes. Our results show that per-lineage dietary niche breadths remained remarkably constant even as snakes diversified to occupy disparate outposts of dietary ecospace. Rapid increases in dietary diversity and complexity occurred in the early Cenozoic, and the overall rate of ecospace expansion has slowed through time, suggesting a potential response to ecological opportunity in the wake of the end-Cretaceous mass extinction. Explosive bursts of trophic innovation followed colonization of the Nearctic and Neotropical realms by a group of snakes that today comprises a majority of living snake diversity. Our results indicate that repeated transformational shifts in dietary ecology are important drivers of adaptive radiation in snakes and provide a framework for analyzing and visualizing the evolution of complex ecological phenotypes on phylogenetic trees.

Evolution of degrees of carnivory and dietary specialization across Mammalia and their effects on speciation

“…A dataset compiled from quantitative data for each of the >5,600 mammalian species would both be a valuable community resource and strengthen the inferences of the current study. However, while it is possible to construct large datasets using such dietary data (e.g., Grundler 2020; Grundler and Rabosky 2021), these datasets require substantial time and effort to produce using standardized estimation approaches and are still limited to several hundred species, rather than the thousands that represent all of Mammalia. To analyze diet across almost all mammals, as in this study, we are currently limited to using comprehensive dietary datasets constructed using qualitative, verbal diet descriptions from secondary sources.…”

Shifts in food webs and niche stability shaped survivorship and extinction at the end-Cretaceous

“…Our results show that the weighted degrees and centrality scores of very small herbivores and small faunivores were almost 10 times greater in the Maastrichtian than in the Campanian. This emphasizes that the latest Cretaceous was also a pivotal time for the trophic and ecological evolution of terrestrial non-dinosaurian vertebrates, as attested by the records of multituberculate, metatherian, and early-diverging eutherian mammals (18,68,72,75), squamates (12,20,76), crocodyliforms (77), and enantiornithine and early-diverging ornithurine birds (7,60).…”

“…On the other hand, groups such as freshwater salamanders, turtles, and crocodylians seemingly survived nearly unscathed (13). In the aftermath of this Cretaceous/Paleogene (K/Pg) mass extinction, surviving lineages recovered relatively rapidly (13)(14)(15)(16), accompanied by concomitant ecospace shifts that favored their expansion into vacated niches and large-scale explosive radiations in placental mammals (17,18), neornithine birds (8,19), and squamates (20), laying the foundations for the diverse range of faunas that we share the planet with today.…”

Giant gar from directly above the Cretaceous–Palaeogene boundary suggests healthy freshwater ecosystems existed within thousands of years of the asteroid impact

“…This event was responsible for the loss of 70-80% of biodiversity [3][4][5], including the infamous demise of the non-avian dinosaurs [6,7]. At the same time, this extinction opened numerous ecological opportunities and is associated with adaptive radiations and prolonged diversifications in major extant lineages like neoavian birds [8][9][10], placental mammals [1,11], snakes [12,13], spiny-rayed fishes [14,15] and flowering plants [16]. Many lineages also experienced a pronounced decrease in average body size across the K-Pg boundary, a phenomenon known as the Lilliput effect [17][18][19].…”