Sexual selection on skeletal shape in Carnivora

Abstract

Lifetime reproductive success of males is often dependent upon the ability to physically compete for mates. However, species variation in social structure leads to differences in the relative importance of intraspecific aggression. Here, we present a large comparative dataset on sexual dimorphism in skeletal shape in Carnivora to test the hypotheses that carnivorans exhibit sexual dimorphism in skeletal anatomy that is reflective of greater specialization for physical aggression in males relative to females and that this dimorphism is associated with the intensity of sexual selection. We tested these hypotheses using a set of functional indices predicted to improve aggressive performance. Our results indicate that skeletal shape dimorphism is widespread within our sample. Functional traits thought to enhance aggressive performance are more pronounced in males. Phylogenetic model selection suggests that the evolution of this dimorphism is driven by sexual selection, with the best-fitting model indicating greater dimorphism in polygynous versus nonpolygynous species. Skeletal shape dimorphism is correlated with body size dimorphism, a common indicator of the intensity of male-male competition, but not with mean body size. These results represent the first evidence of sexual dimorphism in the primary locomotor system of a large sample of mammals.

A disparity between locomotor economy and territory holding ability in male house mice

“…Specialization for economical locomotion is associated with elongation of the limbs, which decreases the number of locomotor cycles to travel a given distance as well as the required rate and amplitude of muscle force generation (Gambaryan, 1974;Hildebrand, 1985;Kram and Taylor, 1990), and reduced distal limb mass, which decreases the energy required to cycle the limbs (Hildebrand and Hurley, 1985;Steudel, 1990). In direct contrast to these traits, specialization for fighting appears to result in stout body plans, greater muscle mass in the distal limbs (Pasi and Carrier, 2003), high mechanical advantages about the limb joints (Morris and Brandt, 2014;Morris and Carrier, 2016), and increased safety factors (Alexander, 1981) in the limb bones to resist high loading in variable directions that may occur during aggressive interactions (Kemp et al, 2005). These contrasting phenotypes may lead to a performance disparity between economical locomotion and fighting ability.…”

Evolution of hyperossification expands skull diversity in frogs

“…The diverse selective pressures proposed to drive extreme derivations in the skull include specializations in feeding biology (1), habitat use (2), and locomotion (3). Sexual selection also is thought to influence head morphology because the skull often is sexually dimorphic in size and shape (4,5). The interactions among these selective pressures can result in functional trade-offs (6) that shape the head as an integrated system that must house the sensory organs, capture prey, provide protection, and partake in locomotion and reproduction (7).…”

Intrasexually selected weapons

“…strength, large muscles, structures conferring mechanical advantage, skeletal support, etc. (Bonnet et al, ; Reaney & Knell, ; Morris & Carrier, )], and fighting style and experience [which influences the outcome of fights (e.g. Hsu & Wolf, ; López & Martín, ; Dugatkin & Druen, ; Hsu, Earley & Wolf, )].…”