Major Patterns in the History of Carnivorous Mammals

The history of carnivorous mammals is characterized by a series of rise-and-fall patterns of diversification in which declining clades are replaced by phylogenet- ically distinct but functionally similar clades. Seven such examples from the last 46 million years are described for North America and Eurasia. In three of the seven turnover events, competition with replacement taxa may have driven the decline of formerly dominant taxa. In the remaining four this is less likely be- cause inferred functional similarity was minimal during the interval of temporal overlap between clades. However, competition still may have been important in producing the rise-and-fall pattern through suppression of evolution within re- placement taxa; as long as the large carnivore ecospace was filled, the radiation of new taxa into that ecospace was limited, only occurring after the extinction of the incumbents. The apparently inevitable decline of incumbent taxa may reflect the tendency for clades of large carnivorous mammals to produce more special- ized species as they mature, leading to increased vulnerability to extinction when environments change.