The tempo of avian diversification during the Quaternary

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Abstract
It is generally assumed that the Quaternary was a period of heightened diversification in temperate vertebrate organisms. Previous molecular systematics studies have challenged this assertion. We re–examined this issue in north temperate birds using log–lineage plots and distributions of sister–taxon distances. Log–lineage plots support earlier conclusions that avian diversification slowed during the Quaternary. To test plots of empirical sister–taxon distances we simulated three sets of phylogenies: constant speciation and extinction, a pulse of recent speciation, and a pulse of recent extinction. Previous opinions favour the model of recent speciation although our empirical dataset on 74 avian comparisons failed to reject a distribution derived from the constant and extinction models. Hence, it does not appear that the Quaternary was a period of exceptional rates of diversification, relative to the background rate.