In spite of the long geographical isolation, the taxonomic status of the marsican bear (Ursus arctos marsicanus) is still not completely accepted. If on the one side genetic analyses supported weakly this Italian endemism as distinct from other European populations of brown bear, on the other side morphological analyses of the cranium suggest that the marsican bear evolved unique features possibly driven by genetic drift and local selective pressures. In many recent studies, the mandible has proved to represent a highly informative mammalian skull component able to discriminate species, to identify ecomorphological adaptations, and to provide reconstructions of feeding ecology in extinct bears. Here, we use mandible size and shape data, quantified by means of 2D landmark based geometric morphometric methods, to test the hypothesis that the marsican bear is morphologically distinct not only from other populations of brown bear, but also from other members of the genus Ursus. Fourteen landmarks were digitized on lateral mandibular projections of specimens belonging to the four Ursus species (U. americanus (n=16), U. thibetanus (n=14), U. arctos (n=78), U. maritimus (n=11)). The landmark configuration was chosen to spatially record the relative position of lower teeth (canine, fourth premolar, carnassial slicing and crushing areas) coronoid, condyle and angular process. Generalized Procrustes superimposition was performed to translate, rotate and scale the landmark configuration of each specimen to a unit centroid size. Principal component analysis, Procrustes ANOVA, and discriminant function analyses demonstrated a strong separation in mandibular morphology of the marsican bear from other populations of Ursus arctos and also from other members of the genus Ursus. The mandible of the marsican bear is characterised by a very thick corpus (both anteriorly and posteriorly), a wider ramus and a highly positioned condyle. All these features could be interpreted in the light of genetic drift or local selective pressures (e.g. diet rich in hard mast). The unique morphological features of Ursus arctos marsicanus should be taken into account for possible future taxonomical evaluation of the brown bear.
The marsican bear (Ursus arctos marsicanus): morphological evidences of taxonomic and ecological distinctiveness
P Colangelo;
2016
Abstract
In spite of the long geographical isolation, the taxonomic status of the marsican bear (Ursus arctos marsicanus) is still not completely accepted. If on the one side genetic analyses supported weakly this Italian endemism as distinct from other European populations of brown bear, on the other side morphological analyses of the cranium suggest that the marsican bear evolved unique features possibly driven by genetic drift and local selective pressures. In many recent studies, the mandible has proved to represent a highly informative mammalian skull component able to discriminate species, to identify ecomorphological adaptations, and to provide reconstructions of feeding ecology in extinct bears. Here, we use mandible size and shape data, quantified by means of 2D landmark based geometric morphometric methods, to test the hypothesis that the marsican bear is morphologically distinct not only from other populations of brown bear, but also from other members of the genus Ursus. Fourteen landmarks were digitized on lateral mandibular projections of specimens belonging to the four Ursus species (U. americanus (n=16), U. thibetanus (n=14), U. arctos (n=78), U. maritimus (n=11)). The landmark configuration was chosen to spatially record the relative position of lower teeth (canine, fourth premolar, carnassial slicing and crushing areas) coronoid, condyle and angular process. Generalized Procrustes superimposition was performed to translate, rotate and scale the landmark configuration of each specimen to a unit centroid size. Principal component analysis, Procrustes ANOVA, and discriminant function analyses demonstrated a strong separation in mandibular morphology of the marsican bear from other populations of Ursus arctos and also from other members of the genus Ursus. The mandible of the marsican bear is characterised by a very thick corpus (both anteriorly and posteriorly), a wider ramus and a highly positioned condyle. All these features could be interpreted in the light of genetic drift or local selective pressures (e.g. diet rich in hard mast). The unique morphological features of Ursus arctos marsicanus should be taken into account for possible future taxonomical evaluation of the brown bear.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
