Evolutionary trends and stasis in carnassial teeth of European Pleistocene wolf Canis lupus (Mammalia, Canidae)

The evolutionary trends of tooth size in quaternary carnivores support an almost direct association with climate. However, phenotypic trait may follow distinct tempo and mode of evolution such as Brownian, Ornstein-Uhlenbeck or random walk. Here, we investigated the morphometric variations and evolutionary trends in the carnassial teeth size of the European wolf (Canis lupus) by means of modern statistical tools. Recent contributions highlighted linear increase trend in tooth size through the Pleistocene, but those differences in time have not been tested using modern statistical strategies. Examining a wide sample of linear measurements of carnassials of extinct and extant wolves (486 M1 and 491 P4), we tested which evolutionary model (random walk, stasis, Ornstein-Uhlenbeck) better explains the dimensional pattern of teeth through time at the continental scale and at the regional scale (France and Italy). Our results clearly show different models for the carnassials of C. lupus. Lower and upper carnassials for the entire sample of C. lupus are characterized by a directional trend, whereas Italian and French subsets show a random fluctuation of carnassials size through time. The carnassials dimensions are not directly correlated with the climate changes during the Middle-Late Pleistocene and Holocene, but they are possibly correlated with spread of the cold mega-fauna in Europe, and thus with the changes in the dietary regime.