Phytogeographic relationships between neotropical and African-Madagascan pteridophytes

Moran. R. C. (The New York Botanical Garden, Bronx, NY 10458-5126, U.S.A.) & A. R. Smith (University Herbarium, University of California, 1001 Valley Life Sciences Bldg. #2465, Berkeley, CA 94720-2465, U.S.A.). Phytogeographi c relationships between neotropical and African-Madagascan pteridophytes. B rittonia 53: 304-351. 2001.-The purpose of this study is to determine the f loristic affinities of pteridophytes between the Neotropics and Africa-Mada gascar and examine how these affinities might have arisen. We present an an notated list that contains two kinds of affinities: 1) species in common be tween both regions (excluding pantropical species) and 2) species pairs (or clusters of species pairs) where one of the species (or infrageneric group ) occurs in the Neotropics and the other in Africa and/or Madagascar. There are 114 examples on the list, of which 27 are same-species and 87 are spec ies pairs or closely related taxa at some infrageneric level. About 13% of the African pteridoflora and 14% of the Madagascan pteridoflora show affini ties with the Neotropics. To determine how these similarities might have or iginated, we assess three hypotheses: 1) the boreotropics hypothesis, 2) co ntinental drift, and 3) long-distance dispersal. The boreotropics hypothesi s is difficult to assess without further phylogenetic information on the gr oups to which the species belong. Continental drift seems to best explain o ne example in the geologically old family Schizaeaceae (species in Anemia s ubgen. Coptophyllum sect. Tomentosae). Nearly all the other examples seem b est explained by long-distance dispersal because they belong to families th at first appeared during the Paleocene, more than 30 million years after dr ift had effectively separated South America and Africa. Most of the dispers al events appear to have taken place from the Neotropics to Africa-Madagasc ar but recent African extinctions may have obscured directionality. Species with green spores or gemmiferous gametophytes were slightly overrepresente d on the list compared to pteridophytes as a whole.