A current overview of the diversity and distribution of Mexican pines

Mexico is considered a secondary center of diversity of the genus Pinus. An analysis of the most recent literature indicates that pines migrated into present-day Mexico from the northern hemisphere through natural corridors and driven by climatic changes in the past. The processes of diversification of the genus occurred in the main mountain ranges of Mexico, which functioned as biological corridors or biogeographic islands that defined the current general distribution pattern of pines in five major regions. Recently, 46 species, 3 subspecies and 22 varieties of pines have been recognized for Mexico. Fifty-five percent of these taxa are endemic. This makes us the most diverse nation in the world with about 42% of the world's species. Mexican pines are one of the most valuable natural resources because of their traditional and commercial use, their cultural importance and the environmental services they offer, but the continuous decrease in pine and pine-oak forest cover due to human activities and forest fires is alarming. At least 20 Mexican pine taxa are in some category of risk and two of them: Pinus maximartinezii and P. muri-cata are in danger of extinction. National and international programs for the sustainable use and conservation of the Pinus genus in Mexico are still not efficient and sufficient.