A morphological analysis of the Mammillaria fittkaui species complex (Cactaceae) reveals a new species from Jalisco, México

Background: The Mammillaria series Stylothelae (Cactaceae) includes 16 taxa distributed mostly among the limits of the Chihuahuan Desert (CD) with the Sierra Madre Oriental and the Transmexican Volcanic Belt (TVB). In Jalisco, four pink flowered species occur at the southwestern end of the CD where it meets the TVB. The boundaries and recognition of three species related with M. fittkaui (M. fittkaui complex) are debatable. Question: Should the taxa of the Mammillaria fittkaui species complex be considered as species? Studied species: Four pink flowered Mammillaria series Stylothelae (M. fittkaui species complex) and M. zeilmanniana as comparative species. Study site: Western Mexico. Methods: Six morphological characters were sampled in specimens from the type locations of three pink flowered species, one locality of Mammillaria sp., and M. zeilmanniana. We used a permutational multivariate analysis of variance on six characters of each of the groups and a discriminant analysis to evaluate the morphological variation among species and to determine the correct classification of each individual. Results: The analyses identified four well defined morphological groups with statistical significance within the Mammillaria fittkaui complex. We recognized M. fittkaui, M. limonensis, and M. manana as species and here describe M. arreolae as a new species from Jalisco. Conclusions: In Cactaceae, morphometry has been useful to establish species boundaries. The Mammillaria fittkaui complex includes four species. Mammillaria arreolae differs from the other species by the shorter tubercles, flowers, and fruits. In addition, it develops more than one hooked central spine per areole.