Mapping

Figure 1: Comparison of NatureServe Ranks and IUCN Red List Categories.

geographic scales: Global (G), National (N) and Subnational (S) (i.e. state and provincial). Subnational level data for all Trillium were gathered from NatureServe’s Network programs through a shared and distributed database, Biotics. These Subnational conservation status ranks and their related spatial data that detail the location, landscape condition and viability of each occurrence of the species in the jurisdiction, give a snapshot of the species’ extinction risk in each state or province. After the Subnational data were reviewed, primary and secondary literature were analyzed for data and information pertaining to species’ Global imperilment as outlined in Faber-Langendoen et al.9 . The resulting Conservation Status Ranks Critically Imperiled (G1) to Secure (G5) (see Figure 1 for details). Conservation status ranks beginning with ‘T’ indicate a Global rank for a variety or subspecies, and should be preceded by the rank for the species, e.g. G4T1. In cases where there are multiple varieties or subspecies, the T ranks will sum to the species’ Global rank. Two additional global ranks, GX (Presumed Extinct) and GH (Possibly Extinct) are also used, and qualifiers “Q” and “C” are used when there is questionable taxonomy or when a species is presumed extinct but extant in cultivation, respectively.

The resulting Red List and NatureServe assessments were reviewed by the Trillium Working Group 2019 at a workshop hosted by Mt. Cuba Center in October 2019.

Mapping

Using ArcMap 10.3.118, taxa were mapped following the IUCN Mapping Standards and Data Quality guidelines19 . It is critical to note that these guidelines are intended to incorporate the totality of a taxon’s natural range and maps may include large tracts of unsuitable habitat. Herbarium specimens and research grade observations from a variety of sources were used to inform the range polygons. Point data used to inform the polygon ranges presented in this volume are available for download along with the individual species assessments for each species at iucnredlist.org20 . In addition to credible point data, published range maps were considered along with textual descriptions of species ranges. In some cases, the results follow biogeographic borders, in others, arbitrary lines following county or state boundaries are considered. The most up to date information was incorporated in each range map, and maps were subsequently reviewed and edited based on the authors’ expertise.