Introduction and Historical Review

Publisher Website
Google Scholar
Abstract
An examination of the literature on the disjunct amphitropical distribution of herbs between North and South America reveals that a very large number of genera and species are involved, and that there is an infinite variety of patterns represented. Attempted explanations have relied chiefly on either long-distance dispersal of some kind in relatively recent times or on the assumption that broadened coastal shelves or formerly less-interrupted mountain systems, together with different climatic regimes, may have permitted readier reciprocal migrations in the past than would appear to be possible at present. It seems likely that both kinds of explanations have validity in different cases, and that no single solution for all such occurrences is to be expected. A few examples from Umbelliferae are offered to illustrate some kinds of situations that may be found in a single family of seed plants.