Species delimitation in the Stenocereus griseus (Cactaceae) species complex reveals a new species, S. huastecorum Author Alvarado-Sizzo, Hernán Instituto de Investigaciones en Ecosistemas y Sustentabilidad (IIES), Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Author Casas, Alejandro Instituto de Investigaciones en Ecosistemas y Sustentabilidad (IIES), Universidad Nacional Autónoma de México, Morelia, Michoacán, México, Author Parra, Fabiola Centro De Investigación De Zonas Áridas (CIZA), Universidad Nacional Agraria La Molina, La Molina, Lima, Perú, Author Arreola-Nava, Hilda Julieta Centro Universitario de Ciencias Biológicas y Agropecuarias (CUCBA), Universidad de Guadalajara, Zapopan, Jalisco, México, Author Terrazas, Teresa Instituto de Biología (IB), Universidad Nacional Autónoma de México, Coyoacán, Ciudad de México, México, Author Sánchez, Cristian Herbario de la Universidad de La Guajira, Riohacha, La Guajira, Colombia text PLoS ONE 2018 e 0190385 2018-01-17 13 1 1 25 http://dx.doi.org/10.1371/journal.pone.0190385 journal article 10.1371/journal.pone.0190385 1932-6203 PMC5771577 29342184 12630726 Stenocereus pruinosus in central Mexico Genetic delimitation fully supports the statements by Parra et al. [ 16 ] about population clusters in northern Mexico (the Huasteca group) and the eastern Tehuantepec Isthmus (the Chiapas group) as species different to S . pruinosus . Moreover, our study confirmed that the latter has a north-south substructure (green shades clusters in the Geneland column in Fig 2 ) which corresponds to the Tehuacán-Cuicatlán Valley and the Oaxaca Central Valleys . S . pruinosus is separated from S . huastecorum by a genetic barrier, consistent with the TMVB , and is separated from S . laevigatus by a second barrier represented by the Isthmus of Tehuantepec, a well-known biogeographic barrier ( Fig 3 ). We did not observe genetic evidence of populations or individuals of S . pruinosus occurring in northern Mexico . Therefore, we do not consider a sympatric scenario between S . pruinosus and S . huastecorum in northern Mexico , but rather a long record of misidentified specimens. Ecological evidence also provides clear distinction of S . pruinosus ENMs from those of S . huastecorum and S . laevigatus given that their comparisons ( Fig 5 , Table 2 ) suggest that these species have different ecological niches. Even though areolar morphology can easily distinguish S . pruinosus from S . huastecorum (every variable measured in Fig 6 ) only spine numbers ( Fig 6E and 6F ) were able to distinguish S . pruinosus from S . laevigatus . Areolar characters, however, may be confusing if developmental features are not taken into account because areolas may lose spines because of flowering events and branch age, or it may be simply deciduous as in central-left and right spines of S . laevigatus . Poor morphological differentiation is clearly related to the fact that this species pair shows the least interspecific genetic distance (Nei’s D = 0.156). This suggests a recent divergence event, which involves the Isthmus of Tehuantepec constraining the distributional range of S. pruinosus to the Tehuacán-Cuicatlán and Oaxaca Central Valleys .