Iterative evolution of large-bodied hypercarnivory in canids benefits species but not clades

Ecological specialization has costs and benefits at various scales: traits
benefitting an individual may disadvantage its population, species or
clade. In particular, large body size and hypercarnivory (diet over 70%
meat) have evolved repeatedly in mammals; yet large hypercarnivores are
thought to be trapped in a macroevolutionary “ratchet”, marching
unilaterally toward decline. Here, we weigh the impact of this
specialization on extinction risk using the rich fossil record of North
American canids (dogs). In two of three canid subfamilies over the past 40
million years, large-bodied hypercarnivory appears to constrain
diversification at the clade level, biasing specialized lineages to
extinction. However, despite shorter species durations, extinction rates
of large hypercarnivores have been mostly similar to those of all other
canids. Extinction was size- and carnivory-selective only at the end of
the Pleistocene epoch 11,000 years ago, suggesting that large
hypercarnivores were not disadvantaged at the species level before
anthropogenic influence.