General Patterns in West Indian Insects, and Graphical Biogeographic Analysis of Some Circum-caribbean Platynus Beetles (Carabidae)

Abstract

The relationships of the Antillean terrestrial arthropodan and onychophoran taxa are reviewed using track analysis, in which tracks are considered the connected areas of ende- mism of cladistically unresolved monophyletic groups. The West Indian fauna is shown to be of complex affinities, with elements related to Central and South America, North America, Africa, Asia, and Australia. Numerous taxa in a variety of insect orders exhibit Antillean-African re- lationships, suggesting that resolved cladistic analyses of such groups will allow testing of vicariance hypotheses of Antillean geohistory. Relationships among taxa on Cuba, Hispaniola and Puerto Rico support a geologic reconstruction in which proto-Hispaniola is composed of eastern Cuba, central and northern Hispaniola and Puerto Rico during the early Tertiary. Cladistic analysis of a clade within the carabid beetle genus Platynus is used to generate taxon- area cladograms. The clade is composed of 32 species, 8 fronf the mainland, 14 from Hispaniola, 4 from Jamaica, 4 from the northern Lesser Antilles, and 2 from Cuba. Fitch optimization is used to generate area transformation series from the taxon-area cladograms. Of the 39 equally par- simonious character cladograms generated in the cladistic analysis, two taxon-area cladograms most parsimoniously account for the area relationships of the Platynus species. These are com- pared to two contrasting geologic hypotheses of area relationships: a mobilist geologic hypothesis and a stabilist geology/taxon dispersal hypothesis. Using component analysis and a graphical representation of the area transformation series, called closed biogeographic graphs, the mobilist geologic hypothesis is shown to better account for the area relationships of the Platynus clade. These area relationsips include: 1) a relatively earlier association of portions of the northern Lesser Antilles with the Greater Antilles; 2) a hybrid origin for Hispaniola, with the central and northern cordilleras related to eastern Cuba, and the southern Haitian peninsula related to Jamaica; 3) a relatively later relationship of Jamaica and northern Central America. The techniques of biogeographic graph analysis are compared to recent attempts at track analysis and to the methods of cladistic biogeography. The biogeographic graphs are shown to be a useful adjunct to component analysis, but suffer from a loss of directed component information. (Biogeography, Caribbean, Carabidae, Platynus, beetles, vicariance.)