Morphotype divergence and genetic diversity of Hedeoma piperita Benth. in western Mexico.

Hedeoma piperita Benth. is a perennial herb from the Lamiaceae family, which is highly valued for its medicinal and culinary properties by the Purépecha ethnic group in Michoacán, Mexico. The species presents populations of two morphotypes (white and purple corollas) that have not been formally studied. In this work, we aimed to evaluate the morphological and genetic variation between the two morphotypes. We sampled individuals from 15 populations within the Purépecha Plateau in western Mexico to measure 33 quantitative and qualitative morphological variable characters (vegetative and reproductive) and to estimate genetic diversity and structure using six nuclear microsatellite markers. Principal Component Analysis showed a clear separation between populations of the two morphotypes, which differences were statistically significant for all vegetative (n = 11) and reproductive (n = 22) characters. Similarly, Bayesian and multivariate cluster analyses based on the microsatellite data supported the distinction of the two morphotypes, except for one population of the white corolla that was genetically closer to the purple corolla group. Genetic diversity was moderate to low across populations of the two morphotypes, and inbreeding (FIS) was significantly higher in populations of the purple corolla. Our morphological and genetic data support the presence of two divergent morphotypes in H. piperita. This species is of high importance within the Purépecha culture, but unfortunately is declining in the region due to its high extraction rates. Thus, our results are valuable to delineate germplasm zones for future breeding programs and for informing in situ conservation strategies.