California’s Sierra Nevada contains a disproportionate share of the state’s plant diversity and is one of the most floristically diverse regions of its size in the United States. The high Sierra Nevada, in particular, has been identified as an important center of species richness and endemism within the State. Anthropogenic climate warming is expected to disproportionately affect mountain ecosystems, and models have predicted habitat contraction and extirpation for many alpine plant taxa. A specimen-based inventory of the vascular plants and bryophytes of Coyote Ridge and Flat was conducted to establish baseline data for one such sensitive alpine and subalpine area. Located in the northwest corner of Inyo County, the study site encompasses 127 km2 (49 mi2) and ranges from 2601 to 4122 m (8535–13,525 ft) in elevation. Coyote Ridge and Flat mark a topographically and geologically unique region of the Sierra Nevada’s eastern slope above the northern Owens Valley and has long been known to botanists for harboring populations of rare and disjunct plant taxa. Fieldwork and herbarium searches conducted between July 2019 and August 2022 documented a total of 542 minimum-rank taxa, 275 of which were not previously known to the area. New collections and examination of historical specimens have yielded occurrences of 13 rare plants new for the area. These include new records for the Sierra Nevada and Inyo County, and one new record for the State of California. Background information for the area, results of this inventory and an annotated checklist of the flora are presented here.

Plants can differ in phenotypes, but genetic variation may not always reflect phenotypic differentiation. In this study, we tested if native, invasive and landrace population types of Brassica tournefortii Gouan diverged genetically. We performed this comparison by genotyping individuals derived from our own field collections (invasive populations) and from USDA accessions (plants from the native range and landraces). We used two polymorphic microsatellite loci to analyze allelic diversity (Question 1), genetic differentiation, admixture, inbreeding (Question 2) and evolutionary relationships (Question 3) of three population types and of 17 populations of B. tournefortii. Comparison of allelic diversity indices and observed heterozygosity among population types, revealed that native populations had, on average, the highest estimates of genetic diversity (Question 1). Overall, the native, invasive and landrace population types had low levels of genetic differentiation and significantly varied in amount of admixture (Question 2). Differences in self-fertilization rates among individuals within populations may have accounted for the microsatellite variation detected. The two microsatellite loci contained enough variability to detect genetic divergence between the native, invasive and landrace population types (Question 3).

The Santa Ana Mountains are a coastal range on the border of Orange and Riverside counties in southern California. Ladd Canyon, covering 18.2 km2 in the Cleveland National Forest, is a botanical black hole relative to the rest of the Santa Ana Mountains because of limited access. It is dominated by chaparral and coastal sage scrub and includes significant knobcone pine (Pinus attenuata) stands and riparian woodland. Features that make it an intriguing area to study include the only serpentine soil in the Santa Ana Mountains, large tracts of habitat that have no recorded fire history, steep topography and relatively low human impacts. To help close the gap in our knowledge of this area, we collected 802 voucher specimens over more than 80 field trips from 2017 to 2022 and produced a vascular plant checklist of 329 taxa, including the rare plants Allium marvinii, Calochortus weedii var. intermedius, Lepechinia cardiophylla, Monardella macrantha subsp. hallii, Monardella hypoleuca subsp. intermedia, Phacelia keckii and several watchlist taxa. We found that knobcone pine stands are closely associated with serpentine outcrops. A relatively low proportion of annual taxa suggests an effect of long fire intervals on the flora of the canyon, and relatively few naturalized taxa are likely the result of infrequent human use and long fire intervals. Oaks in the area can be difficult to key to species, and we discuss their identification and nomenclature. The vascular plant checklist for Ladd Canyon provided here and the herbarium specimens that support it are valuable resources for the study of the flora and ecology of the Santa Ana Mountains.

The Inyo Mountains in Inyo County, California, are an arid mountain range located between the eastern Sierra Nevada and Death Valley National Park. The study site is ca. 433 km2 (167 sq mi), ranging in elevation from 549 to 2955 m (1800 to 9694 ft), and comprises the southern extent of the Inyo Mountains where the Great Basin Desert and Mojave Desert bioregions meet. This area had been poorly represented by botanical collections despite an abundance of distinctive biogeographic features and high diversity in rare and endemic plant species. The objectives of this study were to complete a specimen-based, vascular plant inventory of the southern Inyo Mountains, assess the status of rare species, and evaluate possible edaphic endemics. Searches of herbaria databases resulted in identifying 276 historical collections with the majority occurring along Cerro Gordo Road. Collection efforts for this study were focused on roadless areas and attempted to represent vascular plants from all habitat types. Between June 2018 and June 2021, 102 days were spent in the field, resulting in 950 vascular plant collections. Historical and current collections form the basis of the checklist presented here, which documents 55 families, 191 genera and 368 minimum-rank vascular plant taxa. Nine taxa appear to have a strong association with calcareous substrates and thirty-five taxa have special conservation status in California. A total of 33 taxa are evidently new records for the Inyo Mountains. Much of this ecologically intact and nearly roadless area is critically threatened by mining activities which would impact numerous rare plant species and culturally important plant populations.