Eutrema penlandii

Treated as a species by Rollins (1993) and by Kartesz (1994 and 1999), but included in Eutrema edwardsii by Weber and Wittmann (2012) and FNA (2010). However, U.S. FWS (2019) concludes, "Mastin et al. (2018) published genetic evidence demonstrating that E. penlandii and E. edwardsii have a progenitor-derivative relationship. Chromosome counts, flow cytometry, and population genetic data have revealed that E. edwardsii is an allopolyploid species comprising tetraploid, hexaploid, and octoploid populations. Novel alleles found in the Mosquito Range mustard reveal that E. penlandii is one of two or three diploid progenitors of E. Edwardsii. The two may be discriminated based on novel alleles and patterns of genetic diversity (Hardwick 1997; Bruederle and Hardwick 1998; Hardwick et al in prep), differences in vegetative and reproductive morphology (Fayette and Bruederle 2001; Regier et al in prep; Bruederle, 2020 pers. comm.)), and chromosome counts, which was summarized by Bruederle (2016). Based on the aforementioned, we maintain that the Mosquito Range mustard is a unique and distinct species."

Endemic to a 40 km stretch of the Continental Divide in Colorado where the Divide trends east-west, rather than north-south, and where a unique set of habitat conditions exist, including perennially wet, primarily calcareous soils at very high elevations. The occurrences are in close proximity to mines and are threatened by mineral extraction activities, especially ditching, which could alter the hydrology of the area, and drainage from mine tailings, which could acidify the sites. Recreational use is also a threat, especially from ORVs and hikers. This taxon represents one of only two species of Eutrema in North America, and the only Eutrema in the lower 48 states. This species is disjunct by 1000 miles to its nearest relative Eutrema edwardsii, an arctic circumpolar species.

Eutrema penlandii is a Colorado (U.S.A.) endemic known from Lake, Park and Summit counties. It is limited to a 40 km stretch of the Continental Divide, above 12,000 feet. Range extent is estimated at 242 square kilometers, calculated in GeoCAT by the Colorado Natural Heritage Program (2020).

There are 24 documented occurrences as of 2020; two of the occurrences are considered historical.

The primary threats to Eutrema penlandii at this time appear to be hydrological alterations and mining. Activities that would impact surface water flow include anything from roads, trails, ruts from vehicles, footpaths, ruts, mining construction or any activity of this nature that draws water away from the peat fen habitat (USFWS no date, Plant Profile). Mineral extraction could have a significant impact on this taxon. The mining companies contested the Mosquito Range Research Natural Area; mining remains a big threat to plants in the Mosquito Range because of the thousands of mining claims - a change in the economic viability of mining could cause mining to increase there (Colorado Natural Heritage Program 2004). Also, as mentioned ditching associated with mining could affect the delicate hydrology and could cause water pollution, both of which would adversely affect the species. Recreational use is also a threat including trampling by ORV's and hikers. Any activity that directly or indirectly alters the surface or ground water supply and alters the wetland habitat required by this species could pose a significant threat. In one occurrence, Jeeps and ATVs were parked directly on top of Eutrema plants (Colorado Natural Heritage Program, Element Occurrence data). The impacts of this seemingly benign activity can destroy large areas of this sensitive bog habitat. Another threat to this species are random events that might wipe-out large parts of the already small populations, such as fungal blight, drought, or insect infestations (USFWS no date, Plant Profile). On a larger scale, global warming potentially threatens this and other alpine species.