Growth trajectories in the cave bear and its extant relatives: an examination of ontogenetic patterns in phylogeny

Abstract

BackgroundThe study of postnatal ontogeny can provide insights into evolution by offering an understanding of how growth trajectories have evolved resulting in adult morphological disparity. The Ursus lineage is a good subject for studying cranial and mandibular shape and size variation in relation to postnatal ontogeny and phylogeny because it is at the same time not diverse but the species exhibit different feeding ecologies. Cranial and mandibular shapes of Ursus arctos (brown bear), U. maritimus (polar bear), U. americanus (American black bear), and the extinct U. spelaeus (cave bear) were examined, using a three-dimensional geometric morphometric approach. Additionally, ontogenetic series of crania and mandibles of U. arctos and U. spelaeus ranging from newborns to senile age were sampled.ResultsThe distribution of specimens in morphospace allowed to distinguish species and age classes and the ontogenetic trajectories U. arctos and U. spelaeus were found to be more similar than expected by chance. Cranial shape changes during ontogeny are largely size related whereas the evolution of cranial shape disparity in this clade appears to be more influenced by dietary adaptation than by size and phylogeny. The different feeding ecologies are reflected in different cranial and mandibular shapes among species.ConclusionsThe cranial and mandibular shape disparity in the Ursus lineage appears to be more influenced by adaptation to diet than by size or phylogeny. In contrast, the cranial and mandibular shape changes during postnatal ontogeny in U. arctos and U. spelaeus are probably largely size related. The patterns of morphospace occupation of the cranium and the mandible in adults and through ontogeny are different.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0521-z) contains supplementary material, which is available to authorized users.

Changes in ontogenetic patterns facilitate diversification in skull shape of Australian agamid lizards

“…Although we find strong associations with ecological life habit, this does not preclude the existence of other many important factors, such as diet or patterns of interspecific selection. The weak phylogenetic signal we observe agrees with other studies on the skulls of reptiles [21, 46], mammals [47, 48], and fish [49], that have identified greater associations between morphology and diet [12, 47], feeding habits [49, 50], habitat [24, 51], and environmental factors [49, 52], than with phylogeny. In contrast, some studies confirm a strong phylogenetic signal in morphological variation, such that ecological correlations are not evident [51, 53, 54] or have minimal effect [55].…”

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

“…Previous investigations supported this configuration for being informative both ecologically and taxonomically in Carnivora as well as Ursidae (see Figueirido et al., ; Meloro, , ; Meloro & O'Higgins, ). Although 3D landmarking might provide more detailed information on mandibular size and shape (see Fuchs, Geiger, Stange, & Sánchez‐Villagra, ; van Heteren et al., ), a recent work by Cardini () demonstrated that results between 2D and 3D morphometrics are generally congruent when concerning mammalian mandibles thus allowing substantial generalization to be valid at all scales of biological variation. For species and subspecies taxonomic identification, we followed museum specimen labels and applied nomenclature proposed by Kitchener ().…”

On the growth of the largest living rodent: Postnatal skull and dental shape changes in capybara species (Hydrochoerus spp.)

“…7C). In other studies that investigated both crania and mandibles this difference was also reported (Cardini and O'Higgins, 2004;Christiansen, 2012;Fuchs et al 2015;Segura and Prevosti, 2012). The mandible has been shown to follow a complex ontogenetic trajectory associated with tooth development (Swiderski and Zelditch, 2013).…”