Petalonyx nitidus

Petalonyx nitidus is a shrubby species of deserts in the southwestern United States in southeastern California, southern Nevada, northern Arizona, and historically, southwestern Utah. There are numerous recent reports from BLM, USFS, and NPS lands which provide protection from regional threats, like development. The inaccessibility of the species habitat also affords protection but may contribute to it being underreported. The species distribution and threats are less understood in the eastern part of its range, where it overlaps and is sometimes confused with Petalonyx parryi. Potential threats are climate change, road maintenance, and recreational activities.

Petalonyx nitidus occurs in the southwestern United States in southeastern California, southern Nevada, northern Arizona, and historically, southwestern Utah, largely in the Mojave Desert but also the Colorado Plateau Great Basin (Welsh et al. 2015, FNA 2016, Olson et al. 2001, William and Thompson 1967). The species is likely extirpated from Utah, but surveys are needed to confirm this. While one historical collection could be wrongly attributed to Utah, others from the 1930's were collected from areas that were likely extirpated with significant development in the region (Utah Native Plant Society 2022, Welsh et al. 2015). Based on occurrences in SEINet (2022) and research grade photo-based observations (iNaturalist 2022), range extent was calculated at 143,700 sq km. Range extent is 129,224 sq km when occurrences collected prior to 1993 were excluded. In the eastern part of the species range it overlaps and is sometimes confused with Petalonyx parryi: herbarium specimens and photo observations need to be reviewed to confirm identifications (J. Morefield, pers. comm., 2022).

At least in the western portion of the species range in eastern CA and southwestern NV, there is abundant although largely inaccessible habitat (J. Morefield, pers. comm., 2022). While a review of herbarium records (SEINet 2022) and photo based observations (iNaturalist 2022) suggest around 90 occurrences, this is likely an underestimate.

Threats to this species are mostly undocumented but thought to be low. It is largely protected due to its remote and rugged habitat and a large number of occurrences on protected lands including National Park, National Forest, National Preserve, and Wilderness Areas, particularly in the western part of its range (J. Morefield, pers. comm., 2022). There is less certainty in the eastern part of its range but known occurrences are found in the Grand Canyon National Park. Residential and commercial development and climate change are regional threats (Randall et al. 2010) but many occurrences are protected from development on protected lands. The impacts of climate change on this species are unknown. Other potential threats are road maintenance and recreational activities.