Taxonomie : Broe, Michael [1], Freudenstein, John [1].
Monotropa hypopithys L. (Ericaceae) is a distinct genus with well-defined species segregates at the molecular level.
The Monotropoideae are a herbaceous, achlorophyllous subfamily of the
Ericaceae, within which 12 species in 10 genera are currently
recognized. Most species are endemic to North America, however
two---Monotropa uniflora L. and Monotropa hypopithys
L.---have a much wider distribution in the Americas and Eurasia. We
performed an extensive sampling of monotropoids across N. America, and
here present molecular evidence for a revised treatment of this group
based on ITS1, ITS2 and 26S (approx. 1200 bp). While the two Monotropa
have long been recognized as a single genus, the phylogeny we present
strongly supports the recognition of two distinct genera. Hypopitys (M.
hypopithys) forms a monophyletic group with Pityopus, while Monotropa
sensu stricto (M. uniflora) forms a monophyletic assemblage with
Monotropsis and Monotropastrum (Asia). Hypopitys and Monotropa are
further separated by the intervening genera Allotropa and Hemitomes.
Within Hypopitys
itself species and sub-species have been erected and subsequently
synonymized to a remarkable degree. Small recognized five species in N.
America, while in the most recent monograph Wallace rejected all such
distinctions, choosing to synonymize some 80 putative species,
subspecies and varieties in the Americas and Europe, noting 'there are
no segregates that yet warrant taxonomic recognition'. Our analysis
reveals five geographically circumscribed clades of Hypopitys
in N. America alone---although the pattern is only partially congruent
with Small's analysis---as well as a distinct Eurasian clade. This
contrasts markedly with Monotropa, which exhibits no such structure in
N. America at this level of phylogenetic resolution.
1 - The Ohio State University Herbarium, Evolution, Ecology and Organismal Biology, 1315 Kinnear Rd, Columbus, OH, 43212, USA.
(Oral Paper, Meeting "Botany 2011", Saint-Louis, Missouri, USA)