Cryptic and Overlooked: Species Delimitation in the Mycoheterotrophic Monotropsis (Ericaceae: Monotropoideae)

Abstract—

Most recent treatments of Monotropsis recognize a single species of achlorophyllous, mycoheterotrophic herbs endemic to the southeastern U. S. A. (M. odorata), although four species have been described. This study reevaluates these proposed taxa using a comprehensive approach to species delimitation analyzing variation in morphology, phenology, geography, nuclear DNA, and chloroplast DNA. Principal components analysis of morphometric data reveals two clusters that are geographically distinct. These groups correspond to clades resolved with nuclear (ITS/26S and Xdh) and plastid (rpl32‐trnL) DNA that are furthermore distinct phenologically. These data support recognition of M. reynoldsiae, a Florida endemic and M. odorata, an Appalachian endemic. Monotropsis lehmaniae, proposed based on an autumn flowering period and supposed floral differences, is shown to comprise individuals that are not yet in anthesis, and should not be recognized. Cryptophila pudica, named based on its disjunct geographical distribution and floral differences, is also shown to be indistinct. A taxonomic revision of the genus is presented.