Patterns of maximum body size evolution in Cenozoic land mammals: eco-evolutionary processes and abiotic forcing

Abstract

ResearchCite this article: Saarinen JJ et al. There is accumulating evidence that macroevolutionary patterns of mammal evolution during the Cenozoic follow similar trajectories on different continents. This would suggest that such patterns are strongly determined by global abiotic factors, such as climate, or by basic eco-evolutionary processes such as filling of niches by specialization. The similarity of pattern would be expected to extend to the history of individual clades. Here, we investigate the temporal distribution of maximum size observed within individual orders globally and on separate continents. While the maximum size of individual orders of large land mammals show differences and comprise several families, the times at which orders reach their maximum size over time show strong congruence, peaking in the Middle Eocene, the Oligocene and the Plio-Pleistocene. The Eocene peak occurs when global temperature and land mammal diversity are high and is best explained as a result of niche expansion rather than abiotic forcing. Since the Eocene, there is a significant correlation between maximum size frequency and global temperature proxy. The Oligocene peak is not statistically significant and may in part be due to sampling issues. The peak in the Plio-Pleistocene occurs when global temperature and land mammal diversity are low, it is statistically the most robust one and it is best explained by global cooling. We conclude that the macroevolutionary patterns observed are a result of the interplay between eco-evolutionary processes and abiotic forcing.

Earliest known unequivocal rhinocerotoid sheds new light on the origin of Giant Rhinos and phylogeny of early rhinocerotoids

“…Given the presence of the earliest representative of rhinocerotids in North America28, as well as the poor record of Asian Eocene rhinocerotids and the systematically problematic status of those assigned specimens293839, the North American continent should be central for rhinocerotids at early stage of the evolution. Another evident evolutionary trend is the maximum size of amynodontids and paraceratheriids, which is generally congruent with other Cenozoic large land mammals40. This pattern is greatly contributed to the niche expansion, in which Juxia evolved to the largest terrestrial land mammal Paraceratherium in paraceratheriids (Fig.…”

Feeding ecology has a stronger evolutionary influence on functional morphology than on body mass in mammals

“…For instance, morphological disparity of mammalian teeth is often used as a proxy for dietary diversity, allowing studies to track ecological patterns through time and identify adaptive radiations (Osborn 1902;Simpson 1944;Van Valkenburgh 1988;Janis 1995;Jernvall et al 1996;Wilson et al 2012;Slater 2015;Grossnickle and Newham 2016;Slater and Friscia 2019). Body size (or body mass) is an additional morphological trait that is strongly influenced by ecology (Eisenberg 1981;Peters 1986) and is commonly used as an ecological surrogate in macroevolutionary and macroecological studies (Brown and Maurer 1989;Alroy 1999;Venditti et al 2011;Raia et al 2013;Saarinen et al 2014;Huang et al 2017). Body mass is an especially popular ecological correlate because it is often available in large-scale databases (e.g., Jones et al 2009;Faurby et al 2018) and readily estimated for fossil taxa (Smits 2015;Hopkins 2018).…”

“…Body mass is an especially popular ecological correlate because it is often available in large-scale databases (e.g., Jones et al 2009;Faurby et al 2018) and readily estimated for fossil taxa (Smits 2015;Hopkins 2018). Numerous comparative studies have recently used mammalian body size evolution to examine topics such as rates of evolution, biogeographical patterns, evolutionary trends (e.g., Cope's rule), and extinction risk (Cooper and Purvis 2010;Smith et al 2010;Smith and Lyons 2011;Uyeda et al 2011;Venditti et al 2011;Evans et al 2012;Raia et al 2012;Slater 2013;Tomiya 2013;Saarinen et al 2014;Price and Hopkins 2015;Smits 2015;Huang et al 2017).…”

Space–time patterns of body size variation in island bovids: The key role of predatory release

“…Body size is often regarded as a central aspect of mammal adaptive strategy because it is strongly related to animal architecture and physiology, ecology and ethology (Eisenberg, ; Lomolino et al., ; McNab, ; Saarinen et al., ; Smith et al., ; Van Valen, and references in those papers). Body mass has been considered the best proxy of body size (Gingerich, Smith, & Rosenberg, ), and different allometric equations (based on cranial, teeth or long bones’ dimensions) are available to accurately estimate the body mass of fossil species (e.g.…”