Abstract
The evolution of body mass is a fundamental topic in evolutionary biology, because it is closely linked to manifold life history and ecological traits and is readily estimable for many extinct taxa. In this study, we examine patterns of body mass evolution in Felidae (Placentalia, Carnivora) to assess the effects of phylogeny, mode of evolution, and the relationship between body mass and prey choice in this charismatic mammalian clade. Our data set includes 39 extant and 26 extinct taxa, with published body mass data supplemented by estimates based on condylobasal length. These data were run through 'SURFACE' and 'bayou' to test for patterns of body mass evolution and convergence between taxa. Body masses of felids are significantly different among prey choice groupings (small, mixed and large). We find that body mass evolution in cats is strongly influenced by phylogeny, but different patterns emerged depending on inclusion of extinct taxa and assumptions about branch lengths. A single Ornstein-Uhlenbeck optimum best explains the distribution of body masses when first-occurrence data were used for the fossil taxa. However, when mean occurrence dates or last known occurrence dates were used, two selective optima for felid body mass were recovered in most analyses: a small optimum around 5kg and a large one around 100kg. Across living and extinct cats, we infer repeated evolutionary convergences towards both of these optima, but, likely due to biased extinction of large taxa, our results shift to supporting a Brownian motion model when only extant taxa are included in analyses.
Highlights
Body mass evolution in mammals has been a focus of study since Cope first suggested that there was a directed trend towards larger body mass throughout the Cenozoic Era (Cope, 1887)
Lambda was very close to one (λ = 0.881, p ≪0.001), again supporting strong phylogenetic signal in felid body mass data (Table 1)
Our results show that body mass is strongly linked to phylogeny in Felidae; the specific pattern reconstructed for body mass evolution in felids is highly dependent on whether extinct taxa are included and what dates are used for the fossils in the phylogeny (Table 1)
Summary
Body mass evolution in mammals has been a focus of study since Cope first suggested that there was a directed trend towards larger body mass throughout the Cenozoic Era (Cope, 1887). More recent studies have come to question whether Cope’s Rule applies broadly across large clades, with suggestions that the apparent increases in body mass could be associated with an increase in variance, with no increase in smaller body sizes (i.e., a passive trend, Cope’s rule sensu lato), and that only size increase in both lower and upper bounds, an active trend, should be recognized as Cope’s rule sensu stricto (Stanley, 1973; McKinney, 1986; Gould, 1988; McShea, 1994; Arnold et al, 1995; Novack-Gottshall and Lanier, 2008). As such, understanding body size evolution (and relationship to prey) in cats has immediate significance
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