The transfer of two rare monotypic genera, Neoeplingia and Chaunostoma, to Lepechinia (Lamiaceae), and notes on their conservation

We present an updated circumscription of Lepechinia (Lamiaceae) based on molecular phylogenetic analyses of chloroplast, nuclear ribosomal, and low-copy nuclear genes. In particular, the relationships between Lepechinia mexicana, Neoeplingia leucophylloides, and Chaunostoma mecistandrum, which range from central Mexico down to northern Central America, are explored in detail. We provide strong evidence for recent hybridization/introgression, and not incomplete lineage sorting, between adjacent populations of Lepechinia mexicana and Neoeplingia leucophylloides. The molecular data demonstrate that Neoeplingia leucophylloides and Chaunostoma mecistandrum, two species from monotypic genera with extremely narrow distributions, are embedded within Lepechinia. We formally rename the first as Lepechinia leucophylloides; the latter was previously renamed as Lepechinia mecistandrum. Both of these new Lepechinia species are exceedingly rare and worthy of protection.