Mexico ranks fourth worldwide for its number of species of vascular plants; however, insufficient area has been marked for conservation as Protected Natural Areas (PNAs); 176 PNAs represent 12% of the total surface and encompass only a small portion of the Mexican endemic species. Strategies for setting up conservation zones are often based on identifying biodiversity hotspots to preserve the maximum number of species with the most efficient use of funds. Here we used the richness analysis by grid method based on herbarium specimens to locate zones with a high richness of Cosmos taxa (species and their varieties). Because this approach can lead to omission error, we also obtained an Ecological Niche Model (ENM) for each Cosmos taxon to perform a richness analysis by grid and locate sites with suitable conditions for supporting the most Cosmos taxa. We conducted a panbiogeographic analysis to locate biogeographical nodes, sites of great geobiotic complexity. Western Mexico was thus identified as the highest priority for Cosmos conservation; it has the greatest richness and most suitable conditions for Cosmos and has great biotic complexity. Although one of the largest Mexican PNAs is located in this region, some species with restricted distribution do not occur within this Protected Natural Area (PNA); therefore, a southwest extension of this PNA is proposed.