Reply to: Revisiting life history and morphological proxies for early mammaliaform metabolic rates
Year: 2022
Type: letter
Abstract: We believe the reason for these conflicting results is the differing treatment of extant animal data (body mass, lifespan, and BMR). Specifically: a) Stark et al. 3 include terrestrial, flying/gliding and marine taxa, whereas we include only terrestrial taxa; b) Stark et al. 3 pool captive and wild data whereas we analyse them separately and concentrate on wild extant data for comparison with our fossil mammaliaforms; and c) in some analyses, Stark et al. 3 pool mammals and birds into an ‘endothermic’ sample to be compared to a pooled ‘ectothermic’ sample (non-avian reptiles and amphibians), whereas we compare only terrestrial mammals against non-avian reptiles. Our data treatment was based on a) known exceptions to the relationship between body mass, longevity and metabolic rates (MRs) for flying and marine taxa (whose environments allow, or require, considerably lower or higher body masses, respectively, than terrestrial taxa 4 , 5 , 6 ); b) known differences between maximum wild versus captive lifespans of vertebrate taxa (Newham et al. 1 and references therein, 7 ); and c) considerably different evolutionary histories, and resulting physiologies, of individual clades beyond an endotherm/ectotherm dichotomy. Both studies 1 , 3 identify these factors, but deal with them differently. We 1 limited our extant sample, comparing terrestrial fossil mammaliaforms to terrestrial taxa and analysing wild/captive extant data separately, whereas Stark et al. 3 include flying and marine taxa and pool wild and captive data. While they accounted for wild versus captive lifespans as a predictor in a multivariate model including body mass, sample size and “metabolic rate comparison” (a binary proxy indicating endothermy versus ectothermy), they did not include these factors when analysing BMR in PGLS regressions between longevity, body mass and BMR (Stark et al. 3 Table 1 ). Although they reported nonsignificant differences between wild and captive mammal lifespans (though their reported p = 0.04 (Stark et al. 3 Appendix S3) would seem to indicate significance), we do not consider this a fair test. Wild and captive data for the same taxa are not compared, and wild/captive sample sizes are highly variable between and within the groups considered.
Source: Nature Communications
Authors: Elis Newham, Pamela G. Gill, Michael J. Benton, Philippa Brewer, Neil J. Gostling, David Haberthür, Jukka Jernvall, Tuomas Kankanpää, Aki Kallonen, Charles Navarro, Alexandra Pacureanu, Kelly Richards, Kate Robson Brown, Philipp Schneider, Heikki Suhonen, Paul Tafforeau, Katherine Williams, Berit Zeller-Plumhoff, Ian J. Corfe
Institutions: Queen Mary University of London, Natural History Museum, University of Bristol, University of Southampton, University of Bern, University of Helsinki, University of Oulu, European Synchrotron Radiation Facility, University of Oxford, AIT Austrian Institute of Technology GmbH, University of Portsmouth, Helmholtz-Zentrum Hereon, Geological Survey of Finland
Language: English
Subfield: Paleontology
Field: Earth and Planetary Sciences
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $5,890
OpenAlex ID: W4296827233