Mimulus cusickii

Abstract: Three new species of Diplacus are described. Diplacus cusickii proves to be narrowly endemic to northern Malheur Co., Oregon, and a few localiti es in immediately adjacent Idaho along the Snake River; populations outside of this area previously i dentified as Mimulus cusickii are described here as Diplacus cusickioides Nesom, sp. nov. Plants of the Malheur County population system ( D. cusickii sensu stricto) were identified by Thompson as intermedia te between Mimulus cusickii and M. nanus and the lectotype that he selected for Eunanus cusickii Greene is from this same population system. Diplacus deschutesensis Nesom, sp. nov. , from Crook, Deschutes, Jefferson, Klamath, Lake, and Wheeler counties, Oregon, was regarded by Thompson (2005) as a zone of stabilized hybrids intermediate also between Mimulus cusickii [= D. cusickioides ] and typical M. nanus . The D. deschutesensis population system lies mostly southwest of the range of D. cusickioides and intermediates apparently are few if any. Specimens are cited for the narrow Nevada endemic Diplacus ovatus , which Thompson treated as intermediate between D. cusckii [= D. cusickioides ] and D. nanus var. mephiticus . Diplacus cascadensis Nesom, sp. nov. , from Deschutes, Klamath, and Lake counties, Oregon, has mostly been identified as Mimulus nanus . Ezell (1971) proposed to treat these plants at subspecific rank within M. nanus but the Oregon endemic is distinct from typical D. nanus in morphology and geography. Whether or not the evolutionary orig in of D. deschutesensis , D. cusickii , and D. ovatus involved hybridization, each behaves as a distinct species.