Flora of the core zones of the Monarch Butterfly Biosphere Reserve, Mexico: composition, geographical affinities and beta diversity

Background: Knowing the floristic composition of the Monarch Butterfly Reserve is a critical piece of information necessary for its conservation. Question: i) How many plant species (total and endemic to Mexico) are found in the core zones of the Monarch Butterfly Biosphere Reserve (MBBR)? ii) What are the most frequent growth forms found in this reserve? iii) What is the species diversity for the different types of vegetation? and iv) What is the floristic similarity among the core zones? Studied species: Ferns, Gimnosperms and Angiosperms. Study site and years of study: The three core zone (Cerro Altamirano, Cerro Pelon and Chincua-Campanario-Chivati) of the MBBR were studied from 2000 to 2006. Methods: A total of 49 field trips were conducted over three years (2004 to 2006) to the core zones, and previously collected specimens (2000-2003) were revised in the IEB herbarium. Beta diversity among the core zones was estimated by calculating Jaccard (IJ) index. Results: A total of 97 families, 337 genera, 694 species and 20 infraspecific categories were inventoried. Asteraceae (147 species) and Fabaceae (37), as well as Salvia (23), Quercus (12) and Stevia (12) were the most diverse taxa. Herbaceous plants were the predominant growth form (ca. 75 %). The vegetation types with the greatest number of species were forests dominated by Quercus (427) and by Abies (329). About 38 % of species documented are endemic to Mexico. The core zones show high beta diversity values (Jaccard index 0.03 to 0.11); more of the half of the total number of species documented (66.3 %) was found exclusively in one core zone. Conclusions: The core zones are complementary in terms of plant conservation purposes and require similar conservation resources in order to secure important long-term maintenance of the biodiversity and forest cover that serve as winter refuges of the migrant Monarch butterfly populations.