Mandible size and shape in extant Ursidae (Carnivora, Mammalia): A tool for taxonomy and ecogeography

Abstract

The family Ursidae is currently one of the taxonomic groups with the lowest number of species among Carnivora. Extant bear species exhibit broad ecological adaptations both at inter-and intraspecific level, and taxonomic issues within this family remain unresolved (i.e., the number of recognizable subspecies). Here, we investigate a sample of bear mandibles using two-dimensional geometric morphometrics to better characterize bear taxonomy and evolution with a focus on one of the most widespread species: the brown bear (Ursus arctos). Our analyses confirm that both size and shape data are useful continuous characters that discriminate with very high percentage of accuracy extant bears. We also identify two very distinct mandibular morphologies in the subspecies Ursus actos isabellinus and Ursus arctos marsicanus. These taxa exhibit a high degree of morphological differentiation possibly as a result of a long process of isolation. Ecogeographical variation occurs among bear mandibles with climate impacting the diversification of the whole family.

Geometric morphometric methods as complementary tools to investigate variability in common dolphins (Delphinus sp.) using museum specimens

“…This specific approach has been recommended by Esteban et al (2016) for recently diverged subpopulations of cetaceans. The relevance of multiple approaches variation in wide‐ranging species, especially geometric morphometrics, was recently highlighted in the brown bear Ursus arctos (Colangelo et al, 2012; Hailer et al, 2012; Meloro, Guidarelli, Colangelo, Ciucci, & Loy, 2017).…”

“…The outcomes of this research confirm that geometric morphometrics and museum collections can provide valuable contributions to an integrated approach to taxonomy, combining multiple aspects of genetic, ecological, and phenotypic variations (Padial et al, 2010). As recently highlighted for bears (Colangelo et al, 2012; Hailer et al, 2012; Meloro et al, 2017), this approach has also been recommended for recently diverged subpopulations such as cetaceans (Esteban et al, 2016). This recent divergence is a critical issue for the common dolphin, for which a high degree of geographical variation has been documented by many researchers (Amaral et al, 2012; Bell et al, 2002; Jefferson et al, 2015; Murphy et al, 2006; Murphy, Pinn, & Jepson, 2013; Natoli et al, 2006; Stockin, Pierce, Binedell, Wiseman, & Orams, 2008; Westgate, 2007).…”

Delineating modern variation from extinct morphology in the fossil record using shells of the Eastern Box Turtle (Terrapene carolina)

“…Model-based clustering analyses recovered a single best group containing all specimens. Classification accuracy of subspecies identification based on canonical variates was poor [ 173 ]. Only a little over half of the assignments of specimens to subspecies were correct ( Table 5 ).…”

How flat can a horse be? Exploring 2D approximations of 3D crania in equids

“…Research on anatomical and ecomorphological variation of modern and past representatives of the megafauna, whose partial but rapid extinction on land at the end of the Pleistocene still poses an unresolved dilemma (Koch and Barnosky, 2006), attracts great interest. Indeed, large mammals and birds, but also 'reptiles' such as crocodyles and dinosaurs, have been the subject of innumerable morphological studies, including many 2D GMM analyses (e.g., Pierce et al, 2008;Amaral et al, 2009;Brombin et al, 2009;Figueirido et al, 2009;Brusatte et al, 2012;Christiansen, 2012;Loza et al, 2015;Meloro et al, 2017;Page and Cooper, 2017;Angulo-Bedoya et al, 2019).…”