Mosses and Phytogeography of the Liquidambar Forest of Mexico

Abstract

The known moss flora of the Liquidambar forest of Mexico con- sists of 194 species, 1 subspecies and 7 varieties which can be grouped in 8 phytogeographic elements according to their overall distribution. Four of these elements are strictly American and constitute nearly 70 percent of the total; the remaining 4 have wider ranges. In general this moss flora has a wide altitudinal and latitudinal spread in Mexico as evidenced by high Coefficients of Community and IBD (Index of Biotal Dispersity) values. Historically, the Liquidambar forest moss flora is largely the result of migration at various times through the Central American bridge and Antillean Arc. The present mixture of and species in the Liquidambar forest of Mexico is due to climatic deterioration and altitudinal and latitudinal dis- placement of vegetation in Quaternary time. Certain vegetational communities in eastern Mexico are characterized by a mixture of elements with both tropical and temperate affinities. Miranda and Sharp (1950) characterized these communities and analyzed their floristic relations based primarily on the known vascular flora. Carlson (1954), Crum (1951), Dressler (1954), Hernandez et al. (1951), Martin (1958), Rzedowski (1965), Sharp (1945, 1946a,b), Sharp et al. (1950) and others have also discussed aspects of the phytogeography of taxa within these communities. G6mez-Pompa (1965, 1966), Leopold (1950), Miranda and Her- nandez (1963) and Sousa (1968) have described the vegetation. These publications show that in certain areas of eastern Mexico the flora includes, among others, species of Carpinus, Clethra, Liquidambar, Magnolia, Nyssa, Oreopanax, Ostrya, Podocar- pus, Quercus and Turpinia. However, there is no general agreement on the age of these taxa in Mexico (cf. Braun, 1955; Martin & Harrell, 1957; Sharp, 1953). In this paper aspects of moss distribution, history and floristic relationships of areas of eastern Mexico in which Liquidambar occurs (Fig. 1) are discussed. Some infor- mation on this subject is already available from several publications cited above and such others as Bowers and Sharp (1975), Bowers et al. (1973), Crum and Sharp (1953) and Manuel (1972). To date, however, the moss flora of the Liquidambar forest of Mexico is only partly known, mostly through study of the floristic relations with the southeastern United States. Other geographical relationships have been implied, but not discussed, in previous articles.