Morphology corroborates DNA sequence data in the species-level recognition of Gaultheria trichophylla var. tetracme (Ericaceae)

Résumé

Gaultheria trichophylla var. tetracme of G. series Trichophyllae (Ericaceae) has been distinguished from the nominate variety of G. trichophylla by the presence of two awns on each anther theca (versus one). Phylogenetic data based on plastid DNA sequences placed G. t. var. tetracme in a different clade than the nominate variety with strong statistical support, suggesting that G. trichophylla is not monophyletic. To investigate this further, we studied the morphology of these two taxa in the field and with herbarium material. We found that G. t. var. tetracme differs substantially from the nominate variety in morphology, not only by the number of anther awns, but also the larger size of many features, e.g., plant height, leaves, and pedicels, a greater number of leaf marginal setae, and a distinct geographic range. On this basis, we elevate G. t. var. tetracme to the species level as Gaultheria tetracme, endemic to the Hengduan Shan in Sichuan Province, China. We note the wide morphological variation in the remainder of G. trichophylla and indicate specific problems that should be investigated in more detail for better understanding the taxonomy of this species.