Genus Mammillaria Haw. in the Yucatán Peninsula

Summary: Two species of the genus Mammillaria Haw. are the only globular cacti belonging to the family Cactaceae that have been reported from the Yucatán Peninsula, occurring only in the northernmost coastal areas of the Mexican state of Yucatán. While Mammillaria heyderi subsp. gaumeri is a relatively common cactus inhabiting various types of biotopes (from stabilised coastal sand dunes to dry tropical deciduous forests), Mammillaria columbiana subsp. yucatanensis has been re-discovered in its habitat near Progreso (type locality) only very recently and only a few specimens have been so far reported. Thus, although recorded from other parts of Mesoamerica, M. columbiana subsp. yucatanensis should be considered as a very endangered plant in Yucatán Peninsula, deserving the special protection status. The biggest threat to both cacti is the destruction of their habitats due to the urbanisation of the coastal areas.