| Summary: | Vertebrates have evolved to gigantic sizes repeatedly over the past 250 Myr, reaching their extreme in today's baleen whales (Mysticeti). Hypotheses for the evolution of exceptionally large size in mysticetes range from niche partitioning to predator avoidance, but there has been no quantitative examination of body size evolutionary dynamics in this clade and it remains unclear when, why or how gigantism evolved. By fitting phylogenetic macroevolutionary models to a dataset consisting of living and extinct species, we show that mysticetes underwent a clade-wide shift in their mode of body size evolution during the Plio-Pleistocene. This transition, from Brownian motion-like dynamics to a trended random walk towards larger size, is temporally linked to the onset of seasonally intensified upwelling along coastal ecosystems. High prey densities resulting from wind-driven upwelling, rather than abundant resources alone, are the primary determinant of efficient foraging in extant mysticetes and Late Pliocene changes in ocean dynamics may have provided an ecological pathway to gigantism in multiple independent lineages. Mysticete maximum clade credibility tree Time calibrated maximum clade credibility tree of fossil and extant mysticetes slater_mcct.tre mysticete body lengths Body length data for fossil and extant mysticetes slater_length_data.csv 2008CompilationData delta^18O data from Zachos et al. used to produce proxy temperature curve BEAST 2 xml file used to infer phylogeny of mysticetes under FBD model from morphological and molecular data slater_mysticete_morph_mol.xml SizeEvolutionAnalyses R script to perform macroevolutionary analyses (requires functions script) slater_bodySizeEvolutionAnalyses.R functions Functions required to perform macroevolutionary analyses slater_functions.R simulation_tests Script to perform simulations examining model performance (trend shift model) and sampling bias slater_simulation_tests.R
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