Table 1 Criteria for proposed Tipifarnib mw L-rank system based on area of occupancy using km2 raster grid cells L-rank categories Criteria X = Presumed extinct Not located despite
extensive searches and virtually no likelihood of rediscovery H = Possibly extinct Missing; known from only historical occurrences but still some hope of rediscovery 1 = Critically imperiled Area < 10 km2 (or fewer then ten 1 km2 cells) 2 = Imperiled Area < 50 km2 (or fewer then fifty 1 km2 cells) 3 = Vulnerable to threat or extinction Area < 250 km2 (or fewer then two hundred fifty 17-AAG mw 1 km2 cells) 4 = Apparently secure Uncommon but not rare, some cause for long-term concern due to declines or other factors 5 = Demonstrably widespread, abundant, and secure Common; widespread and abundant In sum, the unique features included in our proposed system for categorizing locally rare taxa are (1) scaling
of the geographic assessment level to correspond with local rarity, the L-rank, and (2) inclusion of defined area of occupancy criteria for L-ranks 1, 2, and 3 NU7441 mouse (Table 1). Thus, a taxon that meets “Critically Imperiled” criteria at all geographical assessment levels could now be labeled G1N1S1L1, representing critical imperilment at global, national, sub-national, and local levels. Likewise, a taxon that is Etoposide ic50 common at the global, national, and sub-national
levels, but rare in a given county, could be labeled G5N5S5L1 and thus receive conservation status within the local jurisdiction. These examples demonstrate how the proposed L-rank system is intended to be viewed as an extension of the NatureServe and IUCN systems that enables local jurisdictions to identify and manage locally rare species. A case study of local rarity Using the flora of Napa County, California as a case study system, we tested the efficacy of the proposed L-rank criteria to classify and catalog the locally rare plant populations of the region. We chose Napa County for our case study due to its high level of plant diversity (Stebbins and Major 1965; Parisi 2003; Crain and White unpublished data) and due to the large number of plant taxa who reach the edge of their range in Napa (Thorne et al. 2004). Furthermore, Napa is rich with geographical and floristic data (Stoms et al. 2005). Although numerous botanical surveys have been conducted in Napa County (Major unpublished data, Stebbins and Major 1965; Jepson Flora Project 2005; CCH 2010) resulting in large databases of plant collection records, no checklist or flora has been published specifically for the region. Therefore, we developed a comprehensive plant checklist for Napa County (Crain and White unpublished data), making both this and future research possible.