Generic and Sectional Delimitation in Onagraceae, Tribe Epilobieae

Abstract

Available evidence is used to produce a revised taxonomy for Onagraceae tribe Epilobieae, with 2 genera, Epilobium and Boisduvalia. Zauschneria is a specialized, bird-pollinated taxon closely related to 1 group of Epilobium, and it is reduced to the status of a section of that genus [Epilobium sect. ZAUSCHNERIA stat. nov. (Zauchneria Presl)]. It is treated as comprising a single species with 3 [E. canum ssp. septentrionale comb. et stat. nov. (Z. cana Greene), E. canum ssp. garrettii comb. et stat. nov. (Z. garrettii A. Nels.) and E. canum ssp. canum] tetraploid (n = 15) and 3 [E. canum ssp. angustifolium comb. nov. (Z. californica ssp. angustifolia Keck), E. canum ssp. mexicanum comb. et stat. nov. (Z. mexicana Presl) and E. canum ssp. latifolium comb. et. stat. nov. (Z. californica var. latifolia Hook] octoploid (n = 30) taxa, between which extensive intergradation occurs. Chamerion (Chamaenerion), a Eurasian group of 7 spp., 2 reaching North America, is closely related to and doubtlessly shares a common ancestor with Epilobium sect. Epilobium; the other 4 sections are more distantly related. They include a total of 7 spp., all xerophytes confined to W. North America, the probable place of origin of the tribe. Boisduvalia is treated as comprising 2 sections in place of the 3 recognized earlier, based upon further morphological studies and evidence obtained from artificial hybridization. The taxonomy proposed for the tribe Epilobieae provides a balanced classification for the group that brings it into line with the other 5 tribes and 15 genera of the family.