Hylinae

Holarctic Hylinae

The predominantly Eurasian Hyla split from the predominantly North American Dryophytes in the Miocene, 22.6 Mya, with the former genus dispersing throughout Eurasia. Subsequent aridification of much of central Asia resulted there in a western clade of eight species of Hyla in what is now Europe and southwestern Asia and a farremoved eastern clade in temperate and subtropical southeastern Asia.

Also in the mid-Miocene 15.4 (13.6–17.3) Mya, the clade that remained in North America differentiated genetically, and evolved into what is recognized as Dryophytes, which occurs throughout temperate eastern North America. Our analysis shows that a stock of Dryophytes dispersed westward across the Bering Land Bridge to Asia in the late Miocene 8.7 (6.6–10.9) Mya. This stock differentiated into three species in eastern Asia (including Japan), the Dryophytes immaculatus Group. The closest relatives of this group, the Dryophytes eximius Group, principally inhabited the pine forests from southwestern United States to Guatemala.

Thus there were two dispersals of hylid frogs across the Bering Land Bridge; temporally these are: (1) Hyla from east to west, and (2) Dryophytes from west to east. In contrast to their Middle American relatives, no lineage of hylines in North America inhabited streams, a habitat that is plentiful in the Appalachian, Rocky, and Sierra Nevada mountain ranges, among others.