Locality: San Nicolas Island, California

Abstract: This checklist documents the vascular flora of San Nicolas Island, one of the eight islands of the California Channel Islands archipelago. The island is situated off the coast of southern California, approximately 61 miles (98 kilometers) from the city of Ventura. The island is approximate 22 square miles (58 square kilometers) in size. The highest point on the island is 910 feet (277 meters) in elevation. San Nicolas Island is owned and operated the the United States Navy. Detailed information on the island and its flora can be found in A Flora of San Nicolas Island by Steve Junak (2008). In the Flora, Junak documents a total of 278 plant taxa occurring on the island, including 137 native and 141 non-native species. Two waves of floristic work have occurred since that time. Carter et al. (2018) documented several new native and non-native plants for San Nicolas, including the first published list of bryophytes for the island. Most of the bryophytes described in that update were new records for the island. This checklist, which will be regularly updated, provides a current synopsis of the flora of San Nicolas Island. Data for the checklist came from field work and study of specimens deposited in herbaria. All information was cross-referenced against Junak (2008) along with the latest taxonomic treatments in regional floras (e.g., The Jepson eFlora, https://ucjeps.berkeley.edu/eflora/). In some cases, taxonomic experts were consulted to assist with determinations. Note that this checklist may depart from previous checklist and Flora efforts with respect to taxonomic inclusion. The checklist includes all vascular plant taxa documented with specimens in recognized herbaria. Noted in the summary below and under each taxon is the presumed status of each taxon on the island, in particular if a plant is considered non-native. Non-native plants are categorized as naturalized, waif, or planted. Total taxa documented in herbaria = 322 Total native and non-native, naturalized taxa = 286 Total native taxa = 151 Total non-native taxa = 171 Total non-native, naturalized taxa = 135 Total non-native, waif or eradicated taxa = 20 Total non-native, planted taxa = 16 Total potentially new taxa found among existing herbarium collections = 9 Total new vascular plant taxa from 2008-2017 field work (Carter et al. 2018) = 7 Total new vascular plant taxa from 2018-2019 field work = 9