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

Jack V. Johnson, Catherine Finn, Jacinta Guirguis, Luke E. B. Goodyear, Lilly P. Harvey, Ryan Magee, Santiago Ron, Daniel Pincheira‐Donoso*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)
42 Downloads (Pure)

Abstract

Aim
The emergence of large-scale patterns of animal body size is the central expectation of a wide range of (macro)ecological and evolutionary hypotheses. The drivers shaping these patterns include climate (e.g. Bergmann's rule), resource availability (e.g. ‘resource rule’), biogeographic settings and niche partitioning (e.g. adaptive radiation). However, these hypotheses often make opposing predictions about the trajectories of body size evolution. Therefore, whether underlying drivers of body size evolution can be identified remains an open question. Here, we employ the most comprehensive global dataset of body size in amphibians, to address multiple hypotheses that predict patterns of body size evolution based on climatic factors, ecology and biogeographic settings to identify underlying drivers and their generality across lineages.

Location
Global.

Time Period
Present.

Major Taxa Studied
Amphibians.

Methods
Using a global dataset spanning 7270 (>87% of) species of Anura, Caudata and Gymnophiona, we employed phylogenetic Bayesian modelling to test the roles of climate, resource availability, insularity, elevation, habitat use and diel activity on body size.

Results
Only climate and elevation drive body size patterns, and these processes are order-specific. Seasonality in precipitation and in temperature predict body size clines in anurans, whereas caecilian body size increases with aridity. However, neither of these drivers explained variation in salamander body size. In both anurans and caecilians, size increases with elevational range and with midpoint elevation in caecilians only. No effects of mean temperature, resource abundance, insularity, time of activity or habitat use were found.

Main Conclusions
Precipitation and temperature seasonality are the dominant climatic drivers of body size variation in amphibians overall. Bergmann's rule is consistently rejected, and so are other alternative hypotheses. We suggest that the rationale sustaining existing macroecological rules of body size is unrealistic in amphibians and discuss our findings in the context of the emerging hypothesis that climate change can drive body size shifts.


Original languageEnglish
Pages (from-to)1311-1322
Number of pages12
JournalGlobal Ecology and Biogeography
Volume32
Issue number8
Early online date25 Apr 2023
DOIs
Publication statusPublished - 01 Aug 2023

Keywords

  • Ecology
  • Ecology, Evolution, Behavior and Systematics
  • Global and Planetary Change

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