Directional selection in the evolution of elongated upper canines in clouded leopards and sabre‐toothed cats

Abstract

Extremely developed or specialized traits such as the elongated upper canines of extinct sabre-toothed cats are often not analogous to those of any extant species, which limits our understanding of their evolutionary cause. However, an extant species may have undergone directional selection for a similar extreme phenotype. Among living felids, the clouded leopard, Neofelis nebulosa, has exceptionally long upper canines for its body size. We hypothesized that directional selection generated the elongated upper canines of clouded leopards in a manner similar to the process in extinct sabre-toothed cats. To test this, we developed an approach that compared the effect of directional selection among lineages in a phylogeny using a simulation of trait evolution and approximate Bayesian computation. This approach was applied to analyse the evolution of upper canine length in the Felidae phylogeny. Our analyses consistently showed directional selection favouring longer upper canines in the clouded leopard lineage and a lineage leading to the sabre-toothed cat with the longest upper canines, Smilodon. Most of our analyses detected an effect of directional selection for longer upper canines in the lineage leading to another sabre-toothed cat, Homotherium, although this selection may have occurred exclusively in the primitive species. In all the analyses, the clouded leopard and Smilodon lineages showed comparable directional selection. This implies that clouded leopards share a selection advantage with sabre-toothed cats in having elongated upper canines.

A multivariate phylogenetic comparative method incorporating a flexible function between discrete and continuous traits

“…First, this study incorporated a feature that has rarely been included in a PCM framework: branch-specific directional selection (Kutsukake & Innan 2013, 2014Harano & Kutsukake 2018). This inclusion was possible thanks to the flexibility of the ABC-PCM, which does not require the mathematical expression or analytic solution of a likelihood function.…”

“…2). ABCs have been shown to facilitate flexible analyses in a comparative framework and therefore have increasingly been applied to PCMs with intricate evolutionary scenarios (Bokma 2010;Slater et al, 2012;Innan 2013, 2014;Janzen et al 2015;Harano & Kutsukake 2018). Briefly, an ABC-PCM estimates parameters of interest by simulating phenotypic evolution without a likelihood function (Beaumont 2010;Csillery et al 2010).…”

Evolutionary Patterns of Cat-Like Carnivorans Unveils Drivers of the Sabertoothed Morphology

“…Stayton metrics ll OPEN ACCESS also retrieved the pair Megantereon nihowanensis and Eusmilus adelos to be significantly convergent, while Castiglione q highlighted convergence or conservatism in the cranium of Neofelis nebulosa and Nimravus brachyops as well as the mandible of Neofelis nebulosa and Metailurus major. Although the clouded leopard was sometimes presented as an example of convergence [35][36][37] with machairodontine felids, it was never compared with nimravids. However, it is clear from Figures 1A and S9A that in this case the clouded leopard does not particularly show a saber-tooth-like craniomandibular shape, whereas Nimravus brachyops and Metailurus major exhibit an incredibly feline-like craniomandibular shape, falling close to extant felines in the morphospace, very close to the oldest felid, Proailurus lemanensis.…”