Diversity and geographical distribution of the genus Sedum (Crassulaceae) in the Sierra Madre del Sur, Mexico

The genus Sedum has 428 species, and 133 grow in Mexico. They are distributed mainly in the Mexican Transition Zone where the Nearctic and Neotropical biogeographic regions converge. The Sierra Madre del Sur (SMS) is one of the most diverse biogeographic provinces in the country. The objectives were: 1) to determine the species richness of Sedum in the SMS, 2) to identify areas with high richness, and 3) to recognize geographical distribution patterns. A database was developed from herbarium specimens and publications. The species richness was quantified by state, vegetation type, biogeographic subprovince, a grid cell of 16 x 16 km and geographical criteria. A total of 429 records were obtained representing 47 taxa, 16 were endemic to the SMS. With 40 species, the highest diversity was concentrated in the districts of Guerrero and Tierras Altas of Oaxaca, in the Oriental subprovince. Most species of Sedum were found in conifer and oak forest. Five areas of high richness were identified in Oaxaca where 6 grid cells were located with 7-10 species. The SMS harbored 47 taxa of Sedum but the diversity and endemism are concentrated in the Oriental subprovince.