The Floristic Composition and Elevational Distribution of Colombian Mosses

Abstract

The moss flora of Colombia is examined in terms of the floristic composition of the nearly 900 species. Overall taxonomic diversity is compared between the eastern North American and Colombian moss floras. It is suggested that temperate and tropical moss diversity may not exhibit a strong latitudinal gradient in species richness from high to low latitudes. Species richness increases with elevation in Colombia, at least to near treeline, in the high montane vegetational zone; at 2,600-3,300 m ca. 50% of the total species diversity occurs. The Andean region, covering ca. 20-25% of the Colombian land surface, contains ca. 93% of the total species diversity for the mosses. An appendix provides several new synonyms and additions to the Colombian moss flora. A dramatic increase in research on neotropical bryophytes has occurred in the last two decades. Floristic work based on recent collections, though somewhat limited, has taken place or is continuing in most countries. Checklists for the mosses are available for nearly all neotropical countries. Fur- thermore, these floristic efforts have also led to a number of phytogeographical studies. Although many groups still remain poorly resolved, revision- ary studies have increased significantly, so that now several families and a number of genera have been treated. However, with the exceptions of the pro- ductive ECOANDES project in Colombia (Van der Hammen & Ruiz 1984; see also Gradstein 1982, 1983, 1990) and BRYOTROP project in Peru (Frey 1987), little has been provided recently concerning various aspects of diversity. Probably the fullest ac- count we have for any single country in the Neo- tropics, at least among the Andean countries, is in the publications on Bolivia by Herzog (1910a,b, 1916, 1920, 1923). The present study attempts to characterize, or at least summarize, our understanding offloristic com- position and general trends in elevational distri- bution patterns of the Colombian moss flora. Some generalizations are also presented about levels of diversity. Establishing general trends and patterns of diversity levels can provide a necessary frame- work in attempting to analyze tropical moss floras. Our attempts to understand diversity may be pre- mature, particularly given the number of poorly re- solved taxonomic groups; however, the current rate of deforestation in the tropics faces bryologists with the necessity of addressing all questions about the comparative biology of mosses now, as is true for all groups of organisms occurring in the tropics. There is a paradox in that by the time we have available regional or worldwide revisionary studies for mosses, providing us with a more precise esti- mate of numbers of species for some parts of the world, we may be addressing questions about ecol- ogy and other aspects of biology of these organisms in the past tense. Colombia is experiencing a continued loss of nat- ural vegetation. According to Gentry (1989), the estimate of 38% extant natural forests in Colombia, largely contributed from the region of Amazonia, may be overstated. Although volumes of literature discuss the diversity and deforestation of wet low- land forests in the Neotropics, not a single book and only a few papers address this subject for montane forests. In terms of vascular plant diversity, the montane and premontane vegetational zones are equal to if not richer than the tropical wet lowlands (cf. Balslev 1988; Gentry 1982). The Andean region has felt the impact of human activities that com- menced at least 3,800-2,900 years BP, and that ac- celerated with the conquest and colonization by Europeans in the mid 1500's (Clawson & Crist 1982; Little 1981). In this century, expansion of agricul- ture, particularly coffee production, coupled with rapid population growth centered in the Andes, have accelerated rates of deforestation of the montane vegetation. Given the very high biodiversity of the Andean region, greater emphasis must be accorded to studies of its biotic inventory and ecology, and greater commitment to conservation of the remain- ing montane forests.