This species may qualify for VU D1, but more research must be done to more accurately estimate total population size.
Some preliminary genetic data suggest that the species delimitation in the Aspicilia determinata group may be revised (S. Leavitt, pers. comm. Jan 2020). However, Aspcilia peltasticoides is phenologically very distinct and likely will remain as currently circumscribed.
This species appears to be rare throughout its restricted range in the Mojave desert of southern California and Nevada.
This species is restricted to siliceous rock in the Mojave desert in southwestern North America. The current Area of Occupancy (AOO) is approximately 34 km², and the current Extent of Occurence (EOO) is 26,050 km². However, we suspect there are undocumented subpopulations yet to be discovered. Fieldwork to date has been concentrated on relatively high elevations in the vicinity of Joshua Tree National Park (Kerry Knudsen, pers. comm. May 2020) and extreme southern portion of Lincoln County, Nevada (Noell & Hollinger 2019). This species is likely to occur in mid to low elevations elsewhere the Mojave, with an EOO probably exceeding 100,000 km², of which less than 10% has been critically surveyed. However, the number of individuals found at the known sites is small (between 1 and ca. 10), so the total number of individuals within the entire region may prove to be less than 1000, which would qualify this species for assessment as VU D1. More research is required to more accurately estimate the population size.
Notes on individual records: There are three documented populations further north in Nevada (CNALH 2020). However, upon re-examination of the collections, they are better placed in Aspicilia determinata s.lat. Some of the early collections by K. Knudsen from near Palm Springs may be misidentified (K. Knudsen, pers. comm. May 2020). These collections should be verified; they reside at the University of California Riverside herbarium (UCR).
Overall, the population appears to be stable based on observations by J. Hollinger and K. Knudsen.
Population Trend: Stable
This species is restricted to siliceous rocks at low to middle elevations in the Mojave Desert (Knudsen & Kocourková 2013).
Rangeland fires are a threat to subpopulations near the ground. Rock climbing is a threat to subpopulations near established and prospective new climbing routes. Note that climbing is very popular at Joshua Tree National Park. Several populations of Aspicilia peltastictoides are known from the park, however none have been found near popular climbing areas yet.
This species currently has no protection status. There are several known sites in one protected area, Joshua Tree National Park.
The Mojave Desert has seen very little attention from lichenologists (Proulx et al. 2016). More floristic work in general is desperately needed in this unique bioregion, and surveys targeting suspected rare or threatened species such as Aspicilia peltastictoides throughout the region are required. For A. peltastictoides, it is important to design methodology carefully to provide accurate estimates of total population size.
Sequences of the ITS locus in the fungal mitochondrial DNA suggest that some specimens on calcareous rock previously called Aspicilia determinata may actually belong to A. peltastictoides (S. Leavitt, pers. comm. Jan 2020). If so, this species may not be as rare as currently thought. The A. determinata group is particularly common and diverse throughout the Intermountain Region, an area well known for its poor representation in lichenological literature. Taxonomic questions such as the identity of these aberrant calciphilous specimens can only be answered in the context of a broader revision of the A. determinata group.
Surveys for the species in rock climbing areas are also needed, along with quantitative studies of the degree of climbing impact.
This species has no known commercial or cultural value.
CNALH. 2020. Biodiversity occurrence data published by: ASU, FH, hb. Hollinger (Accessed through CNALH Data Portal, http//:lichenportal.org/cnalh/index.php, 20 May 2020)
Knudsen, K. & J. Kocourková. 2013. Lichenological notes 6: nomenclatural acts. Mycotaxon 124: 353–359.
Noell, N. & J. Hollinger. 2019. The Lichen Flora of the Caliente Field Office, Lincoln County, Nevada. Bureau of Land Management, Nevada State Office, 1340 Financial Boulevard, Reno, Nevada.
Proulx, M.W., K. Knudsen & L.L. St. Clair. 2016. A checklist of Mojave Desert lichens, USA. North American Fungi 11(6): 1–49.