The effect of sampling effort and methodology on range size estimates of poorly-recorded species for IUCN Red List assessments

Abstract Geographic range size is the most commonly implemented criterion of species’ extinction risk used in IUCN Red List assessments, especially for poorly-recorded species. applies two contrasting measures to capture different facets a distribution: Extent Occurrence (EOO; Criterion B1) area bounding all known occurrences and proxy spatial autocorrelation risk, while Area Occupancy (AOO; B2) occupied within this boundary related population at finer grains. Various methods have been proposed measure both EOO AOO. We evaluate impact applying four each B1 B2, as well key parameter choices, on status 227 neotropical pteridophyte Between 2 100% species would be considered threatened depending methodology. The minimum convex polygon method estimating was relatively robust sampling effort but least-recorded IUCN-recommended AOO summing × km grid cells very strongly correlated with total number records. It likely that only small fraction can adequately assessed using method, we recommend caution particular, where models predicting occupancy unsampled areas (e.g. distribution models) may provide more accurate assessments. vital methodological information retained comparisons should made between assessments utilising equivalent methods.