Evolution and systematics

Molecular evidence indicates that the family Ochotonidae (pikas) separated from the family Leporidae (the other family in the order Lagomorpha) 37 million years ago. Paleon-tological evidence closely matches this date, suggesting that the two families separated in the early Oligocene. All evidence points to an Asian origin for the family. Pikas spread to North America by the late Oligocene. Pikas quickly differentiated into many forms and became particularly diverse during the Miocene. During this time, representative genera were found in North America, Asia, and Africa. The first Ochotona appeared in the early Pliocene of Asia, and Ochotona first entered North America in the mid-Pliocene. Ochotona and Prolagus, the only other pika genus to reach historical times, are first found in Europe during the late Pliocene. Prolagus subsequently went extinct, leaving Ochotona as the only living representative of the family from a record of 25 fossil genera.

The close resemblance of all pika species makes it difficult to find external characters to tell them apart. Even using traditional morphological measurements on skull bones and dentition has not been sufficient to stem controversy over the systematic alignment of pika species; no two revisions of the genus are the same. Some subspecies have landed in as many as four different species. Molecular techniques have begun to clarify pika systematics, and a consensus is nearing, although the task is far from completed. Currently, 30 species of Ochotona are recognized.

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