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Keywords:

  • —Lepidoptera;
  • —biogeography;
  • —dispersal;
  • —vicariance;
  • —plate tectonics;
  • —Indo—Australian tropics

The Indo-Australian tropical archipelagos have increased in extent and proximity through the Tertiary whilst also changing their configuration. The development of new land areas between old cratonic ones involves extensive dispersals of plants and animals from the latter to the former. The vicariance approach, though suited to the study of the fragmentation of old, cratonic land areas, is of uncertain value in this situation; the representation of emergence or convergence and fusion of land areas in cladogram form presents immense problems and to attempt it may be pointless.

Distribution of Lepidoptera species largely reflects the present day geography of the area for both lowland and montane habitats. Significant discordances at a higher taxonomic level can be examined in the light of hypotheses of past geography such as those concerning the evolution of the Melanesian Arcs.

There are many advantages and some disadvantages in using Lepidoptera for such studies, involving their taxonomy, completeness of geographical coverage, range of dispersal ability and specificity to environmental conditions. Both cladistic and phenetic methods can provide basic data for biogeographic studies. The importance of an understanding of habitat preferences is stressed.

Patterns of probable recent development involving well-defined groups of very similar species are examined in the hope they will provide a yardstick whereby potentially older patterns can be assessed, and lead in time to methodology that will satisfy the stringent requirements of current thinking in the philosophy of science.