1996; White 1999; Draper et al. 2003). Therefore, we focus specifically on these geographic measures to develop our proposed local rarity ranking system. Classifying local rarity Based on our review of NatureServe’s and the IUCN’s systems, we establish a new local assessment level (L-rank) for categorizing

OSI906 locally rare taxa within local jurisdictions and geographic regions. Under this proposed system, a taxon will be considered locally rare if it meets minimum LCZ696 area of occupancy levels using grids composed of 1 km × 1 km (1 km2) cells. Although grids composed of 2 km × 2 km cells are commonly used in factoring the G, N, and S ranks, data were available at a 1 km2 scale. Cells of this size create a more accurate picture and thereby alleviate some of the problems associated with models based on larger cell sizes (Thuiller et al. 2008). At the same time, 1 km2 cells are compatible with other commonly used metric grids (e.g., 1 ha or 100 km2 cells), thus simplifying conversion of data to other scales. Moreover, unlike global, national, or sub-national assessments, it is less prohibitive to collect local data at the 1 km2 scale within a reasonable amount of time and level of effort. Accordingly, the L-rank category is an incorporation and modification

of aspects of the NatureServe and IUCN systems Erastin and is specifically designed to be used in conjunction with NatureServe’s original geographic assessment scales. To identify and classify locally rare taxa through geographic analysis, we outline specific area of occupancy criteria to designate different levels of rarity at the local scale. While we lend our support to the IUCN’s explicit area of occupancy criteria for larger scales, the same numbers cannot be logically applied to local assessment levels due to the fact that many local jurisdictions are relatively small and have an overall area of <2,000 km2, the maximum range to be considered for conservation status Resveratrol (IUCN 2001). If the IUCN’s area of occupancy criteria were applied to these

small jurisdictions, taxa distributed throughout the entire county would still meet the minimum criteria for conservation status at the local assessment level. Therefore, we created new area of occupancy criteria specifically for the local assessment level (Table 1). Numerical criteria were chosen qualitatively based upon analysis of criteria used by other systems, available information on average county sizes in the United States, and reviews of research showing the effects of range size on susceptibility to environmental and biological stressors. The “Critically Imperiled” range size criteria of 10 km2 used in our system is based directly on the IUCN criteria for “Critically Endangered” as it is a good measure of extreme rarity and vulnerability.