Do richness estimators anticipate what is found later? A back-test with marine occurrence records from 160 sea areas
Zenginlik kestiricileri sonradan bulunanı öngörüyor mu? 160 deniz alanında deniz canlısı kayıtlarıyla bir geri-test
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Abstract
Non-parametric richness estimators are widely used to judge how complete regional species inventories are, but their predictions are rarely confronted with what is later found. We used the Ocean Biodiversity Information System to reconstruct, for 66 large marine ecosystems and 100 IHO sea areas, the animal species inventory as it stood with records collected to 1999, 2009 and 2019, and compared estimates made from the earlier inventories with the species actually recorded by 2026. Inventories built from records to 1999 appeared 75% complete by the Chao1 estimator (median). By 2026 the number of recorded species exceeded the 1999 estimate in 76% of areas and its upper 95% confidence bound in 64%; the 1999 inventories held at most 66% of the species now known. Four alternative estimators were exceeded in 52–79% of areas. When the 2026 inventories were randomly thinned to the 1999 number of records, Chao1 was exceeded in 55% of areas, so the excess failure reflects how records accumulate through new places, methods and taxa, not sample size. The estimators still carried information: predicted and realised increases were correlated (Spearman 0.36), and a recalibrated model combining the estimate with record growth explained 51% of ten-year inventory growth out of sample, against a negative R² for the uncorrected estimate. Current estimates suggest that inventories are 80% complete in the median large marine ecosystem; such figures should be read as upper bounds and used for ranking, not as absolute measures of what remains to be found.
Keywords
Species richness estimation; Inventory completeness; Chao1; OBIS; Large marine ecosystems; Knowledge shortfalls
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