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Diffusion – Publications scientifiques Muséum national d’Histoire naturelle CP 41 – 57 rue Cuvier F-75231 Paris cedex 05 (France) Tél. : 33 (0)1 40 79 48 05 / Fax : 33 (0)1 40 79 38 40 [email protected] / http://sciencepress.mnhn.fr © Publications scientifiques du Muséum national d’Histoire naturelle, Paris, 2020 ISSN (imprimé / print) : 1280-9659/ ISSN (électronique / electronic) : 1638-9395 Ecometrics and Neogene faunal turnover: the roles of cats and hindlimb morphology in the assembly of carnivoran communities in the New World P. David POLLY Earth and Atmospheric Sciences, Indiana University 1001 E. 10th Street, Bloomington, Indiana (United States) [email protected] Submitted on 17 February 2019 | accepted on 20 April 2020 | published on 2 July 2020 urn:lsid:zoobank.org:pub:FE4A6D79-2153-44C6-9711-CF71061E6768 Polly P. D. 2020. — Ecometrics and Neogene faunal turnover: the roles of cats and hindlimb morphology in the assembly of carnivoran communities in the New World, in Bonis L. de & Werdelin L. (eds), Memorial to Stéphane Peigné: Carnivores (Hyaenodonta and Carnivora) of the Cenozoic. Geodiversitas 42 (17): 257-304. https://doi.org/10.5252/geodiversitas2020v42a17. http://geodiversitas.com/42/17 ABSTRACT Cats possess some of the highest ankle gear ratios of any extant carnivorans, a feature that facili- tates leaping and sprinting involved in ambush predation and scansorial lifestyles. In today’s North American carnivoran communities, the high gear ratio of cats contributes to an overall high ecometric average for this trait and contributes strongly to measures of ecometric disparity at the community level. But cats were late additions to North American communities, arriving from Eurasia about 17 Ma at the end of the “cat gap”. This paper uses ecometric analysis to document changes in hindlimb functional diversity in North American carnivoran communities over the last 19 million years in order to better understand the roles of trait evolution, clade turnover, and environmental change in community assembly. To accomplish this, I look at the phylogenetic history of ankle gear ratios of cats and other carnivorans, and the history of their occupation of high gear ratio niches in North American communities. The primary focus is on the Great Plains, which experienced profound changes in vegetation and climate through this period. Across all Carnivoramorpha, including a variety of extinct clades, it was found that gear ratios range from 1.08 (with extant ursids and viver- rids and extinct miacids and barbourofelids, one of the three cat groups considered in this paper, having the lowest values) to 1.46 (with extant felids, herpestids, and canids having the highest val- ues). Using the fossil record combined with phylogenetic ancestor reconstruction, it is shown that stem carnivorans and early felids had gear ratios about halfway between these extremes, consistent with a semidigitigrade or mildly digitigrade stance that was not overly specialized for either leaping or sprinting. Barbourofelids and some machairodontines evolved lower gear ratios that emphasized mechanical efficiency over advantage. When cats first entered North American communities in the KEY WORDS Miocene they did not occupy high gear ratio niches and, in fact, occupied some of the lowest gear Carnivora, ratio niches during the Barstovian, Clarendonian, and Hemphillian. A major restructuring of gear Felidae, ratio distributions in North American carnivoran communities occurred during the Blancan that ecometrics, functional trait ecology, appears to have resulted from clade sorting processes involving the selective loss of low gear ratio locomotor morphology. groups, as well as the evolution of increased gear ratios in felids and canids. GEODIVERSITAS • 2020 • 42 (17) © Publications scientifiques du Muséum national d’Histoire naturelle, Paris. www.geodiversitas.com 257 Polly P. D. RÉSUMÉ L’assemblage des communautés félines du Nouveau Monde : écométrie et changements fauniques du Néogène. Les félins possèdent une cheville avec un indice calcanéal parmi les plus élevés chez les carnivores actuels, un caractère qui facilite le saut et le sprint impliqués dans la prédation par ambuscade et dans un mode de vie de grimpeur. Cet article pose des questions sur l’origine phylétique de cet indice et sur l’histoire de l’occupation par les félins de niches nécessitant un indice élevé. Parmi tous les carnivoramorphes, on a trouvé que l’indice varie de 1.08 (ursidés ou viverridés actuels, miacidés et barbourofelidés ayant les plus faibles valeurs) jusqu’à 1.46 (félidés, herpestidés et canidés ayant les plus hautes valeurs). En utilisant la reconstruction d’un ancêtre phylogénétique, on a montré que le Carnivora ancestral et le félidé ancestral avaient des indices à mi-chemin entre les extrêmes, corres- pondant à des attitudes digitigrades ou semi-digitigrades qui n’étaient pas complètement spécialisées pour la course ou le saut. Les bardourofélidés et quelques machairodontes possédaient des indices MOTS CLÉS très bas mettant l’accent sur l’efficacité mécanique plutôt que sur les autres avantages. Les félidés du Carnivora, Felidae, Miocène d’Amérique du Nord n’occupaient pas des niches nécessitant un indice élevé et, de fait, écométrie, occupaient des niches avec indices faibles pendant le Barstovien, le Clarendonien et l’Hemphillien. écologie des traits Une restructuration majeure de la distribution des indices dans les communautés de Carnivora en fonctionnels, morphologie Amérique du Nord s’est produite durant le Blancan avec des processus de tri des clades en fonction locomotrice. de la perte sélective des groupes possédant des indices faibles. INTRODUCTION a community and the environment in which the community is situated (Ricklefs & Travis 1980; Poff 1997; McGill et al. Cats make a unique contribution to the locomotor diversity 2006). Ecometrics is an evolutionary ecological approach to of extant carnivoran communities. Predominantly leapers the study of community assembly that breaks the specializa- and springers, cats are among the most digitigrade of living tions of its species down into quantitative functional traits, carnivores and have higher ankle gear ratios than most other whose distributions and evolution can be studied across space carnivorans, including their cursorial canid cousins (Fig. 1). and through time (Polly et al. 2011; Polly & Head 2015). By While canids and felids share a pronounced digitigrade stance, focusing on distributions of individual traits instead of species, the function of felid limbs is more strongly differentiated ecometrics recognizes that species are composites of traits, between fore and hind than in canids (Meachen-Samuels & Van often with unique combinations that collectively differentiate Valkenburgh 2009; Kitchener et al. 2010). The felid forelimb it from other taxa, as in felids and canids, which have similar is less suited for parasagittal cursorial locomotion and more hind limb gear ratios but different combinations of forelimb suited for grappling