Stenocereus laevigatus

Alvarado-Sizzo, Hernán, Casas, Alejandro, Parra, Fabiola, Arreola-Nava, Hilda Julieta, Terrazas, Teresa & Sánchez, Cristian, 2018, Species delimitation in the Stenocereus griseus (Cactaceae) species complex reveals a new species, S. huastecorum, PLoS ONE (e 0190385) 13 (1), pp. 1-25 : 19-20

Stenocereus laevigatus in southern Mexico

In Chiapas and Yucatán there are up to three SGSC members records ( Fig 1 ). Genetic clustering showed dominance of a single genetic group ( Fig 3 ) that we consider to be S. laevigatus given that its records are more common than those of other taxa. Secondary genetic structure involving the westernmost populations of Umoa and Cintalapa (Chiapas) was detected by Geneland, Barrier, and UPGMA analyses. This break contrasts with the nesting pattern showed by the Yucatán Peninsula populations within the Chiapas group ( Fig 3 ), even when they are separated by a distributional gap of over 500 km.

We consider the greater genetic divergence within the same region in Chiapas as an indicator of either recent demographic processes or occurrence of artificial selection. Human management is common throughout the distributional range of S. laevigatus , and it is particularly strong in Chiapas. Management has been previously recognized as a genetic-landscape modifier in S. stellatus [ 38], but historic demography and phylogeographic research are still needed to distinguish between biogeographic and human processes.

Even though this species is genetically and ecologically divergent with respect to S. pruinosus , if only morphology is taken into account, they may arise as cryptic species given that areolar features are very similar or actually identical in young or vegetative branches.

Figures

Fig 1. Distribution of the Stenocereus griseusspecies complex (SGSC) taxa, as considered by Arreola-Nava [15].

Fig 3. Genetic clustering summary. Color gradients represent BC belonging probability starting from the 75% threshold value, purple bars with green types bootstrap values are the three genetic barriers detected by Barrier, at the left the UPGMA dendrogram following the color code used in the BC. https://doi.org/10.1371/journal.pone.0190385.g003