Revision of Heuchera Section Rhodoheuchera Subsections Hemsleyanae and Rosendahliae Subsectio Nova (Saxifragaceae)

Abstract—

A revision of a closely allied and poorly studied group of Mexican Heuchera species is presented. This work has necessitated several taxonomic and nomenclatural actions, namely: the recognition of the name H. longipetala as referring to the Mexican plant usually known as H. hemsleyana; the reduction of the latter to synonymy; the description of two new species, H. rosendahlii and H. wellsiae , having such divergent morphology as to warrant a new subsection, subsection Rosendahliae ; the transfer of H. mexicana to subsect. Hemsleyanae; the description of a new variety for H. mexicana ( H. mexicana var. potosiensis ) and for H. longipetala ( H. longipetala var. nudicaulis ); the reduction of H. orizabensis to a variety of H. longipetala ( H. longipetala var. orizabensis ) and of H. amoena to a synonym of H. mexicana; and the lectotypification of the names H. orizabensis and H. hemsleyana. Provided are descriptions, notes on habitat and phenology, range maps, line drawings, and full specimen citations for all taxa treated, as well as a taxonomic key for all known species of Heuchera in Mexico, new chromosome counts for two taxa, and a morphological cladistic analysis of section Rhodoheuchera.