A new critical estimate of named species-level diversity of the recent Mollusca

摘要

Modern estimates of species-level diversity in the recent Mollusca range from 34,000 to 120,000 described species, with total diversity including undescribed species often cited as 200,000. Most estimates are unverifiable, not being based on reproducible methods. Ultimately the best way to gauge diversity is explicit enumeration: actual listing of known species. Comprehensive lists of species are valued as a basis for systematic revisions and for comparing diversity across taxa, but it is less appreciated that they also provide a means for statistical sampling of biodiversity databases. I assessed the completeness of molluscan species listings in the World Register of Marine Species (WoRMS) by comparing it to a standardized inventory of the species represented in the Malacology collection of the Academy of Natural Sciences of Philadelphia (ANSP). Random samples of names were scored for presence or absence in WoRMS, with standard errors calculated from the binomial distribution. The WoRMS database has about 1,200 duplicate or extraneous listings for mollusk species and is missing about 1,300 (3%). Overall marine molluscan diversity is estimated at 43,600 900 species, where 900 is a 95% confidence interval. The validity of this confidence interval depends on the WoRMS database and the ANSP collection not having correlated weaknesses. Lack of relatively complete species databases prevents similar assessments for terrestrial and freshwater mollusks, but, using less rigorous methods, I estimate that there are 70,000 to 76,000 described species of recent Mollusca.