Altitudinal distribution patterns of Mexican cloud forests based upon preferential characteristic genera

Abstract

Mexican cloud forest vegetation has been recorded in temperate humid conditions at rather different elevations ranging from 600 to 3000 m. They are characterised by high biodiversity under continuous foggy situations. Some authors state that many genera are quantitatively important to depict cloud forest conditions. Detailed quantitative studies comprising most of the localities of Mexican cloud forests to depict altidudinal distribution ranges on basis of preferential genera have not been previously conducted. The aim of this study is (1) to recognise characteristic preferential genera of Mexican cloud forest conditions, and (2) to determine quantitatively the current altitudinal distribution pattern of this vegetation type. From a database composed by 995 genera inhabiting in the Mexican cloud forests, six genera were chosen preliminary as preferential characteristics. These were Clethra, Magnolia, Meliosma, Styrax, Symplocos, and Ternstroemia. These genera include 70 species that occur at over 70% of the current Mexican cloud forest fragments. The mean elevation of these genera records were 1853 m (+/- 600 at 95% confidence interval). The results showed that Mexican cloud forests occur optimally between 1250 and 2450 m. Additionally, Mexican cloud forest is the best distributed within some provinces of the "Region Mesoamericana de Montana", chiefly at "Serranias Meridionales", "Sierra Madre Oriental", and "Serranias Transistmicas". The results are discussed in light of the importance of these regions as diversification centres.