The collapsing populations of large herbivores will have extensive ecological and social consequences.

National and local initiatives focused on the transformation of STEM teaching in higher education have multiplied over the last decade. These initiatives often focus on measuring change in instructional practices, but it is difficult to monitor such change without a national picture of STEM educational practices, especially as characterized by common observational instruments. We characterized a snapshot of this landscape by conducting the first large scale observation-based study. We found that lecturing was prominent throughout the undergraduate STEM curriculum, even in classrooms with infrastructure designed to support active learning, indicating that further work is required to reform STEM education. Additionally, we established that STEM faculty’s instructional practices can vary substantially within a course, invalidating the commonly-used teaching evaluations based on a one-time observation.

Living rodents show great diversity in their locomotor habits, including semiaquatic, arboreal, fossorial, ricochetal, and gliding species from multiple families. To assess the association between limb morphology and locomotor habits, the appendicular skeletons of 65 rodent genera from 16 families were measured. Ecomorphological analyses of various locomotor types revealed consistent differences in postcranial skeletal morphology that relate to functionally important traits. Behaviorally similar taxa showed convergent morphological characters, despite distinct evolutionary histories. Semiaquatic rodents displayed relatively robust bones, enlarged muscular attachments, short femora, and elongate hind feet. Arboreal rodents had relatively elongate humeri and digits, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. Fossorial rodents showed relatively robust bones, enlarged muscular attachments, short antebrachii and digits, elongate manual claws, and reduced hind limb elements. Ricochetal rodents displayed relatively proximal insertion of muscles, disproportionate limbs, elongate tibiae, and elongate hind feet. Gliding rodents had relatively elongate and gracile bones, short olecranon processes of the ulnae, and equally proportioned fore and hind limbs. The morphological differences observed here can readily be used to discriminate extant rodents with different locomotor strategies. This suggests that the method could be applied to extinct rodents, regardless of ancestry, to accurately infer their locomotor ecologies. When applied to an extinct group of rodents, we found two distinct ecomorphs represented in the beaver family (Castoridae), semiaquatic and semifossorial. There was also a progressive trend toward increased body size and increased aquatic specialization in the giant beaver lineage (Castoroidinae).

The fossil record of the order Carnivora extends back at least 60 million years and documents a remarkable history of adaptive radiation characterized by the repeated, independent evolution of similar feeding morphologies in distinct clades. Within the order, convergence is apparent in the iterative appearance of a variety of ecomorphs, including cat-like, hyena-like, and wolf-like hypercarnivores, as well as a variety of less carnivorous forms, such as foxes, raccoons, and ursids. The iteration of similar forms has multiple causes. First, there are a limited number of ways to ecologically partition the carnivore niche, and second, the material properties of animal tissues (muscle, skin, bone) have not changed over the Cenozoic. Consequently, similar craniodental adaptations for feeding on different proportions of animal versus plant tissues evolve repeatedly. The extent of convergence in craniodental form can be striking, affecting skull proportions and overall shape, as well as dental morphology. The tendency to evolve highly convergent ecomorphs is most apparent among feeding extremes, such as sabertooths and bone-crackers where performance requirements tend to be more acute. A survey of the fossil record indicates that large hypercarnivores evolve frequently, often in response to ecological opportunity afforded by the decline or extinction of previously dominant hypercarnivorous taxa. While the evolution of large size and carnivory may be favored at the individual level, it can lead to a macroevolutionary ratchet, wherein dietary specialization and reduced population densities result in a greater vulnerability to extinction. As a result of these opposing forces, the fossil record of Carnivora is dominated by successive clades of hypercarnivores that diversify and decline, only to be replaced by new hypercarnivorous clades. This has produced a marvelous set of natural experiments in the evolution of similar ecomorphs, each of which start from phylogenetically and morphologically unique positions.

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Bending strength of upper canine teeth is examined among living canids, felids, hyaenids and several extinct species including sabretooth cats, borophagine dogs and the dire wolf, Canis dirus. The tooth is modelled as a cantilever with an elliptical cross‐section. Using beam theory, the bending strength of the upper canine is calculated given a constant force applied to the canine tip. Results indicate that felids and hyaenids have relatively stronger canines than canids, particularly in bending about the anteroposterior (AP) rather than the mediolateral axis. It is suggested that canine shape reflects the forces produced during killing and feeding. As shown by an analysis of jaw muscle moment arms, felids and hyaenids have relatively stronger bites than canids. Moreover, the canines of hyaenids and felids are perhaps more likely to contact bone during feeding and killing and consequently may be subjected to larger and more frequent bending moments about the AP axis. The canines of sabretooth cats are shown to be more similar in shape and strength characteristics to those of living canids than felids, whereas those of the borophagine dogs and the dire wolf are closer to modern hyaenas.

Over the past 50 million years, successive clades of large carnivorous mammals diversified and then declined to extinction. In most instances, the cause of the decline remains a puzzle. Here we argue that energetic constraints and pervasive selection for larger size (Cope's rule) in carnivores lead to dietary specialization (hypercarnivory) and increased vulnerability to extinction. In two major clades of extinct North American canids, the evolution of large size was associated with a dietary shift to hypercarnivory and a decline in species durations. Thus, selection for attributes that promoted individual success resulted in progressive evolutionary failure of their clades.

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