Zoogeography of the Northern Hemisphere and amphibians: the Palearctic and the Nearctic vs. the Holarctic?

Abstract

Various schemes, proposed by zoologists and botanists of the second half of the 19th century and the first third of the 20th century, to unite temperate parts of the Northern Hemisphere (the Palearctic and Nearctic realms) in a single biogeographic region under the names “the Boreal Region” or Realm, “the Arctogaean Region”, “the Triarctic” or “the Holarctic”, and “Periarctic region” are briefly outlined. The history of the concept of the Holarctic (A. Heilprin 1883, 1887) and of its critics by Alfred Wallace and Theodore Gill are described. Based on the list of amphibian families and their zoogeographic distribution provided by A. Wallace (1876b), our re-evaluation by means of the Czekanovsky–Sorensen Coefficient confirmed Heilprin’s conclusion about larger similarity between the Palearctic and the Nearctic in comparison with their neighbouring zoogeographic regions. However, the same quantitative analysis of the distribution of amphibians (at the level of families, genera as well as species) in these five regions, based on modern taxonomy evidenced for significant distinctness of amphibian faunas of the Palearctic realm and the Nearctic realm and, thus, did not support the reality of the Holarctic for amphibians.