Ecological Specialization in Fossil Mammals Explains Cope’s Rule

2012/02/09 by Pasquale Raia, P. Raia, F. Carotenuto +7 · 100 citations
Earth and Planetary Sciences · Mathematics · #Bergmann's rule #Biology #Clade #Ecological niche #Ecology #Evolution and Paleontology Studies #Evolutionary biology #Geography #Latitude #Lineage (genetic) #Morphological variations and asymmetry #Niche #Origination #Paleontology and Evolutionary Biology #Phylogenetics #Selection (genetic algorithm)

paper · doi:10.1086/664081

published in The American Naturalist 179(3), 328-337 (University of Chicago Press)

openalex publication_date 2012/02/09 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/27

Abstract

Cope's rule is the trend toward increasing body size in a lineage over geological time. The rule has been explained either as passive diffusion away from a small initial body size or as an active trend upheld by the ecological and evolutionary advantages that large body size confers. An explicit and phylogenetically informed analysis of body size evolution in Cenozoic mammals shows that body size increases significantly in most inclusive clades. This increase occurs through temporal substitution of incumbent species by larger-sized close relatives within the clades. These late-appearing species have smaller spatial and temporal ranges and are rarer than the incumbents they replace, traits that are typical of ecological specialists. Cope's rule, accordingly, appears to derive mainly from increasing ecological specialization and clade-level niche expansion rather than from active selection for larger size. However, overlain on a net trend toward average size increase, significant pulses in origination of large-sized species are concentrated in periods of global cooling. These pulses plausibly record direct selection for larger body size according to Bergmann's rule, which thus appears to be independent of but concomitant with Cope's.

Citations

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