Species Status Assessment Report for the San Clemente Island larkspur (Delphinium variegatum ssp. kinkiense) Version 1.0 Image courtesy of US Navy March 2020 U.S. Fish and Wildlife Service Pacific Southwest Region Sacramento, CA ACKNOWLEDGEMENTS This document was prepared by the Texas A&M Natural Resources Institute in cooperation with the U.S. Fish and Wildlife Service and the United States Navy as part of the Service’s San Clemente Island Species Status Assessment Team. We would like to recognize and thank the following individuals who provided substantive information and/or insights for our SSA: Sula Vanderplank, Dawn Lawson, Jon Rebman, Kim O’Connor, Bryan Munson, and Melissa Booker. Additionally, valuable input into the analysis and reviews of a draft of this document were provided by Mitchell McGlaughlin and Andrea Williams. We appreciate their input and comments, which resulted in a more robust status assessment and final report. Suggested reference: U.S. Fish and Wildlife Service. 2020. Species status assessment report for the San Clemente Island larkspur (Delphinium variegatum ssp. kinkiense), Version 1.0. March 2020. Sacramento, CA. SSA Report – San Clemente Island larkspur ii March 2020 EXECUTIVE SUMMARY This Species Status Assessment (SSA) provides an analysis of the overall species viability for the San Clemente Island larkspur (Delphinium variegatum ssp. kinkiense). To assess the viability of this subspecies, we, the U.S. Fish and Wildlife Service, used the conservation biology principles of resiliency, redundancy, and representation (3 Rs). Specifically, we identified the subspecies’ ecological requirements and resources needed for individual survival and reproduction. We described the stressors (threats) influencing these resources and evaluated current levels of population resiliency and subspecies redundancy and representation using available metrics to forecast the ability of this subspecies to sustain populations into the future. The San Clemente Island larkspur is an herbaceous perennial in the buttercup family (Ranunculaceae) that is endemic to San Clemente Island (SCI) off the coast of California. The San Clemente Island larkspur was federally listed as endangered on August 11, 1977. A five-year status review was completed in 2008 and recommended reclassification of the subspecies from endangered to threatened. A request for new information during an initiation for a new five-year status review was issued in 2010; no updated 5-year review has been published. San Clemente Island larkspur is one of two subspecies of Delphinium variegatum that occur exclusively on SCI, the other being Thorne’s larkspur (Delphinium variegatum spp. thornei). A third subspecies, Royal larkspur (D. v. spp. variegatum), occurs on the mainland. The taxonomic separation of San Clemente Island larkspur from Thorne’s larkspur is not very definitive from field observation. When the two subspecies were described, there were fewer locations and individuals known on the island, and the island subspecies were distinguished primarily by flower color, with Thorne’s larkspur noted to have generally bright blue (i.e., darker), slightly larger flowers than the San Clemente Island larkspur, which generally has white flowers. While this taxonomic treatment is still used, these color and flower size metric distinctions do not adequately separate these taxa. San Clemente Island larkspur occurs mostly in the northern portion of the island, and Thorne’s larkspur occurs in the southern portion of the island. However, in the middle of the island (and on the far southern end), the two flower colors coexist in many locations, with varying proportions of each color, and flower colors ranging from pure white to dark purple. Thus, expert opinion, genetic research, and careful consideration of taxonomic challenges sheds doubt on the existence of two distinct taxa on SCI, and it has been suggested that the two subspecies may be a single taxon separate from Delphinium variegatum or that the two subspecies might be better described as varieties. Genetic research using allozyme data to validate two taxa was inconclusive, and only additional genetic research can determine whether there are any significant genetic differences between the two flower forms present on the island. However, from a regulatory perspective, locations and individuals currently recognized as San Clemente Island larkspur must be assumed as such, and these are the focus of this assessment, although we account for locations where the population appears to be mixed or otherwise in question. Like most other California larkspurs, San Clemente Island larkspur can survive below ground when conditions are unfavorable and may remain dormant and not appear above-ground for one or more years. We assume that the subspecies is relatively long-lived. Because of this dormancy, and additionally because flower production in Delphinium can be highly variable and may be dependent upon quite localized weather conditions, exact numbers of individuals are difficult to locate and count. The subspecies is generally found within mid- to high- elevation grasslands on the east side of the northern and central portions of the island where it occurs in SSA Report – San Clemente Island larkspur iii March 2020 clay, loam, and rocky soils with soil-depths ranging from shallow to deep; however, it is more often associated with non-clay soils. Reported habitats have included costal grasslands as well as grassy slopes and benches, open grassy terraces, and chaparral and oak woods. Using a strict ruleset to avoid overcounting the subspecies and segmenting the island population by watershed for counting/management purposes, we estimate there are currently 18,956 individuals within 22 watersheds on SCI. Another two watersheds are known to be occupied, but data do not exist for estimated numbers of individuals. Two additional watersheds do not contain locations identified as San Clemente Island larkspur; however, these watersheds occur in an area where white individuals have been noted to be prominent within groups, and thus, we assume these groups are of mixed subspecies. We find that the subspecies currently has generally high levels of resiliency within watersheds and as a population overall, appears to have sufficient representation, based on the diverse areas it occupies and genetic studies, and sufficient redundancy, occupying many of the same areas it has been known to historically and increasing in numbers and distribution since listing. At listing under the Endangered Species Act (ESA), nonnative herbivores were the primary threat to San Clemente Island larkspur. As a result of their removal by 1992, habitat conditions improved and led to increases in the cover of native and nonnative plants on the island, including San Clemente Island larkspur and several other threatened and endangered species. In the absence of the primary threat, additional threats to San Clemente Island larkspur that have been identified include: (1) land use, (2) erosion, (3) nonnative plants, (4) fire and fire management, and (5) climate change. SCI is owned by the U.S. Department of the Navy (Navy) and, with its associated offshore range complex, the island is the primary maritime training area for the Pacific Fleet and Sea Air and Land Teams (SEALs) and supports training by the U.S. Marine Corps, the U.S. Air Force, and other military organizations. As such, portions of the island receive intensive use by the military and can involve the movement of vehicles and troops over the landscape and can include live munitions fire, incendiary devices, demolitions, and bombardment. However, very few individuals exist within these training areas; less than 1% of the population occurs in a training area that gets heavy use. Current erosion issues are localized, and erosion is generally decreasing on the island as the vegetation continues to recover. While San Clemente Island larkspur exist in watersheds where erosion resulting from the Assault Vehicle Maneuver Areas (AVMAs) could impact an estimated 344 individuals, an Erosion Control Plan is expected to prevent or correct erosion that may occur as a result of military operations and training in the AVMA. One other location of an estimated 70 individuals exists near a road where erosion impacts are projected to be higher, but still, this threat is minor. While not much is known about the tolerance of the subspecies to fires of different severities or frequencies, based on field observations and closely related species, fire does not appear to negatively impact San Clemente Island larkspur, and may even benefit the subspecies. We assume that San Clemente Island larkspur is not threatened by fire on SCI. Non-native annual and perennial grasses are widespread on SCI and have been for many decades. No assessment to track these invasive plants within occupied habitat areas has been done, but none is indicated at this time. San Clemente Island larkspur is found within naturalized, non-native grasslands, and there is the potential that these exotic annual grasses could out- compete San Clemente Island larkspur or affect fire regimes, making fires more likely. However, SSA Report – San Clemente Island larkspur iv March 2020 it does not appear as if these grasses are expanding, and they have been present during the recorded fire history, so we do not expect fire patterns to change due to these non-native grasses. The factor that appears to have the most potential to impact species viability in the future