1972/12/01 by Robert F. Thorne · 7 citations
Agricultural and Biological Sciences · #Botany, Ecology, and Taxonomy Studies #Plant Diversity and Evolution #Botanical Research and Chemistry
paper · doi:10.1086/407399
In attempting to review and classify the major intercontinental disjunctions in the geographic ranges of seed plants, six guiding principles are followed where possible. Sixteen categories and 34 subcategories of disjuct ranges of intercontinental magnitude (Table 1) are classified according to continents and latitudinal bands involved. Widely distributed taxa are, by their very nature, disjunct; they are therefore classified along with the more traditionally discontinuous types. Thus, for the most part, only endemics and taxa with smaller intracontinental disjunctions are omitted from this review. Generalized distribution maps are presented for selected taxa characteristic of each of the dicontinuous types. Other taxa are listed for each of the categories and subcategories, and compendia of good distribution maps are cited for ready reference to additional examples. Possible explanations for the major discontinuities are discussed. Finally, a statistical summary is given of the numbers of disjunct taxa and the largest disjunct categories. Among the Angiospermae (the flowering plants), approximately 78 per cent of the 324 families, 24 per cent of the genera, and 1 per cent of the species are widely disjunct. The largest number of disjunct genera are found among the African-Eurasian-(Pacific) (600), Asian-Pacific (460), Pacific (370), North American-South American (ca. 360), Pantropical (334), North Temperate (316), and Subcosmopolitan (125) categories; the largest number of disjunct families among the Subcosmopolitan (90), Pantropical (59), North Temperate (20), African-Eurasian (Pacific) (17), and North American-South American (13) categories.