A Wallace biography

3 Advent of the Wallace Line

In 1858 P. L. Sclater divided the world into zoogeographic regions on the basis of their faunas. Sclater’s divisions were based on terrestrial forms, and in particular the distribution of groups of birds.  In his article On the general geographical distribution of the members of the class Aves, Sclater divided the globe into six zoogeographical realms:

  1. Palaearctic,
  2. Aethiopian,
  3. Indian (Oriental),
  4. Australian,
  5. Nearctic, and
  6. Neotropical.

These major divisions of the globe are still recognised today.

Sclater's zoogeographic divisions
Sclater’s zoogeographic divisions of the world

Sclater (1858) attempted to define the Indian or Oriental region:

“Another tropical region of the Old World seems to be constituted by Southern Asia and the islands of the Indian Archipelago. The Philippines, Borneo, Java, and Sumatra, certainly belong to this division, but it is of course not yet possible to decide where the line runs which divides the Indian zoology from the Australian. “

Wallace in his remarks on Sclater’s paper in the journal Ibis in 1859 (Letter from Mr. Wallace concerning the Geographical Distribution of Birds) stated of the Indian region:

“Its south-eastern limits I draw between the islands of Bali and Lombok, and between Celebes and Borneo, and the Moluccas and the Phillipines. Barbets reach Bali, but not Lombok; Cacatua and Tropidorhynchus (= Philemon, a friarbird) reach Lombok, but not Bali: this I think settles the point.”

He further remarked:

“There is perhaps no fact connected with geographical distribution more extraordinary, and at first sight inexplicable, than the division of such an apparently homogeneous tract as the Indian Archipelago between two provinces which have less in common than any other two upon the earth.”

Thus Wallace had defined the line which now bears his name.

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