Moss Distribution and the Phytogeographical Significance of the Neovolcanic Belt of Mexico

Abstract

Moss distribution suggests that there has been extensive floristic exchange among the major alpine areas of the Neovolcanic Belt of Mexico. Although the large number of shared taxa is a measure of the intensity of the exchange, certain taxa are of limited distribution; several are restricted to the eastern mountains while others are unknown from the higher elevations of the western side. The floristic and age differences among the mountains indicate that moss migration has not been unidirectional nor synchronic. Besides its role as a floristic bridge, the Neovolcanic Belt seems to have limited the dispersal of some mosses in a north-south direction; a barrier effect in a south-north direction is not supported by the known distribution of mosses in Mexico. The moss floras from the southern valleys may have moved northward even before mountain building, but present exchange between northern and southern valleys may take place through corridors across the Neovolcanic Belt.