What drives the evolution of body size in ectotherms? A global analysis across the amphibian tree of life

Aim The emergence of large-scale patterns animal body size is the central expectation a wide range (macro)ecological and evolutionary hypotheses. drivers shaping these include climate (e.g. Bergmann's rule), resource availability ‘resource rule’), biogeographic settings niche partitioning adaptive radiation). However, hypotheses often make opposing predictions about trajectories evolution. Therefore, whether underlying evolution can be identified remains an open question. Here, we employ most comprehensive global dataset in amphibians, to address multiple that predict based on climatic factors, ecology identify their generality across lineages. Location Global. Time Period Present. Major Taxa Studied Amphibians. Methods Using spanning 7270 (>87% of) species Anura, Caudata Gymnophiona, employed phylogenetic Bayesian modelling test roles climate, availability, insularity, elevation, habitat use diel activity size. Results Only elevation drive patterns, processes are order-specific. Seasonality precipitation temperature clines anurans, whereas caecilian increases with aridity. neither explained variation salamander In both anurans caecilians, elevational midpoint caecilians only. No effects mean temperature, abundance, time or were found. Main Conclusions Precipitation seasonality dominant amphibians overall. rule consistently rejected, so other alternative We suggest rationale sustaining existing macroecological rules unrealistic discuss our findings context emerging hypothesis change shifts.