Geographical and floristic delimitation of the Balsas Depression physiographic province, Mexico, with emphasis on the seasonally dry tropical forest

Biogeographic regions are defined by endemic or characteristic species and particular physiographic features. The floristic delimitation of the Balsas Depression province in central-western Mexico and the biomes was carried out using cartographic layers (sub-basins and elevation) and herbarium records of its vascular flora. The Balsas Depression has an extension of 115,007 km2. The elevation threshold that delimits the seasonally dry tropical forest, the biome with the largest area in the Balsas Depression (74,548 km2), is found from sea level to 1,627 m of elevation. The circumscription of the biomes based on a biogeographical analysis using vascular plants revealed the existence of 10 floristic groups (Phytochoria), 2 of which stand out, and delimit the tropical seasonally dry and temperate forests, respectively. The flora ' s delimitation both physiographically and floristically and its regionalization allowed us to propose a methodological strategy potentially useful for defining geographic limits in other areas of interest.