Flora of North America species comparison

Species 7 (7 in the flora).

Species of Eremothera are found mainly in the interior deserts and bordering areas of the western United States.

R. A. Levin et al. (2004) found strong molecular support for paraphyly in the broadly delimited Camissonia of P. H. Raven (1969). There was some support for a clade of Camissonia and Eremothera and another clade of Camissoniopsis, Neoholmgrenia, and Tetrapteron (Levin et al.), but without morphological features linking the members of these two clades. The monophyletic subclades of these two clades were recognized as genera by W. L. Wagner et al. (2007) whereas they were all treated by Raven as clearly distinguishable sections. Raven recognized four distinct groups within Eremothera (as Camissonia sect. Eremothera): E. refracta and its autogamous derivative, E. chamaenerioides; the very diverse E. boothii (with six subspecies) and two rare autogamous derivatives, E. gouldii and E. pygmaea; the local clay endemic E. nevadensis; and the widespread autogamous and often cleistogamous E. minor. Levin et al. included one species from each of these four groups in their molecular analyses and found strong support for Eremothera as circumscribed by Raven and maintained by Wagner et al. Eremothera is well defined by white petals that open in the evening and an entire, subglobose stigma; some species are visited by moths at anthesis and by bees the following morning (Raven). Reproductive features include: self-incompatible (E. boothii, E. refracta, and, possibly, E. nevadensis) or self-compatible; flowers vespertine; outcrossing and pollinated in the evening by small moths and the following morning by bees, in E. boothii subsp. decorticans by large oligolectic andrenid bees (E. G. Linsley et al. 1963, 1964, 1973), or autogamous, rarely cleistogamous (Raven).

(Discussion copyrighted by Flora of North America; reprinted with permission.)

Genera 13, species 265 (12 genera, 199 species in the flora).

Onagreae account for more than half the total genera in Onagraceae and diversified from a center in southwestern North America (L. Katinas et al. 2004). Delimitation of the tribe by W. L. Wagner et al. (2007) differs from previous ones by the exclusion of Gongylocarpus, now in its own tribe, by the segregation of eight genera (Camissoniopsis, Chylismia, Chylismiella, Eremothera, Eulobus, Neoholmgrenia, Taraxia, and Tetrapteron) from Camissonia, and by the inclusion of three previously separate genera (Calylophus, Gaura, and Stenosiphon) in Oenothera. Within the branch of the family that lacks stipules (Gongylocarpeae, Epilobieae, and Onagreae), the last two tribes form a clade that has very strong molecular support (R. A. Levin et al. 2003, 2004), but no obvious morphological synapomorphy. The clade may be defined by a cytogenetic change from the base chromosome number of x = 11 found in Circaeeae, Gongylocarpeae, and Lopezieae, to x = 18 in Epilobieae, and x = 7 in Onagreae; however, these changes could also have occurred independently. Other than the new chromosome number x = 7, the only apparent morphological synapomorphy for Onagreae alone is pollen with prominent apertural protrusions (J. Praglowski et al. 1987, 1989), a character state also found in Circaeeae (Praglowski et al. 1994). The monophyly of Onagreae has moderate (Levin et al. 2004) to strong support (V. S. Ford and L. D. Gottlieb 2007).

(Discussion copyrighted by Flora of North America; reprinted with permission.)