A New Species of Tigridia and Species Richness and Endemism Distribution of the Tribe Tigridieae (Iridaceae) in the Sierra Madre Del Sur, Mexico

The Sierra Madre del Sur (SMS) biogeographic province parallels the Pacific Ocean from the state of Jalisco to Oaxaca and Puebla. The area is very complex tectonically and geologically and harbors the highest number of vascular and endemic plant species in Mexico. Here, we describe Tigridia nana as a new species in this province. Furthermore, during the revision of herbaria and digital collections, we created a database to provide a biogeographical analysis of Tigridieae in the SMS. Morphologically, T . nana pertains to Tigridia subgenus Tigridia. . The nectary has secretory trichomes that extend across the inner tepal, the base of the much reduced limb inflexes, and then covers it. Tigridia nana is endemic to Oaxaca coexisting in the SMS with 34 other species of Tigridieae. The group is very diverse in the state of Oaxaca, with the species richness and endemism concentrated in the Oaxacan Highlands district. The pine-oak forest harbors the greatest species richness. Our findings coincide with the species richness and endemicity values of some other plant groups in the SMS.