Daniele De Angelis, Narimane Chatar, Margot Michaud, Carlo Meloro, Denise Crampton, Leopoldo Soibelzon, Maria E. Arnaudo, Luciano Varela, Sebastián P. Tambusso, Luigi Maiorano

Bears (Ursidae, Carnivora) are considered keystone species in several ecosystems, besides their potential impact on early human migrations and habitat use. Fitness variations linked to phenotypic and/or ecological adaptations might be rendered using evolutionary landscapes meant to show differences in selective advantage of specific traits, even indicating the most morphologically- and ecologically-distinctive species for eco-evolutionary and conservation aims. Here we investigate morphological and ecological evolutionary landscapes within living and extinct ursids. To do so, three dimensional geometric morphometrics was applied to a total of 69 bear crania belonging to 23 living and extinct species to collect shape data. Furthermore, ecological variable scores were obtained relying on species occurrences from online databases (PaleobioDB, GBIF) and pre-existing literature, combined with paleoclimatic data (PALEO-PGEM). Our results suggest that strongest morphological and ecological adaptive peaks are mainly occupied by extinct derived morphotypes (i.e., short-faced bears). Both morphological and ecological landscapes show that many living species (e.g., genus Ursus) occupy a weakest selective optimum, whereas extant specialists (e.g., polar bears, pandas) are far from the strongest peaks. These evidences suggest that most of living bears are characterized by non-extreme morphologies and ecological niches that probably give them higher ecomorphological flexibility than their fossil counterparts, which occupied stronger selective peaks at the expenses of an increased extinction risk (e.g., potential occurrence of ratchet-like mechanisms in short-faced bear evolution).