A DATABASE APPROACH TO STUDIES OF MOLLUSCAN TAXONOMY, BIOGEOGRAPHY AND DIVERSITY, WITH EXAMPLES FROM WESTERN ATLANTIC MARINE GASTROPODS

A system of data fields and conventions is introduced that will allow workers on any group of mollusks to build interactive databases docume nting classifications, synonymies, geographic and bathymetric ranges, and other summary information at the species level. This system is use d to build a database which is the first comprehensive catalogue of Re cent Western Atlantic gastropods ever assembled with geographic covera ge extending from Greenland to Antarctica. As of January 1993, the dat abase contained 8370 records, of which 3988 represent currently recogn ized species, 3491 are synonyms, 157 are nomina dubia and the remainde r are misidentifications, misspellings, invalidly published or extrali mital. There are 3103 currently recognized species of tropical Western Atlantic gastropods (35-degrees-N to 24-degrees-S); 2641 of these had been named by 1971, when Keen documented 2438 gastropod species in th e tropical Eastern Pacific. The common perception that the tropical We stern Atlantic fauna is depauperate compared to the Eastern Pacific ca nnot be supported. Faunal lists corrected for synonymies, variant gene ric combinations and misidentifications were extracted from the databa se for eight areas in the tropical Western Atlantic. These are eastern and western Florida, Yucatan, Panama, Jamaica, Puerto Rico, the Nethe rlands Antilles and northern Brazil. To correct for regional collectin g biases, species smaller than 5 mm, those occurring only deeper than 50 meters, and those lacking external shells were excluded from the li sts. In 28 pairwise comparisons among the standardized lists, 27 showe d faunal similarities greater than 50%. Western Florida, which lacks s hallow reefal habitats, had faunal similarities lower than did eastern Florida, which has these habitats. Habitat availability seems as impo rtant as geographic distance in determining faunal similarity within t he tropical Western Atlantic. None of the eight regions had more than 4% endemic species. Although species tend to be widespread within the tropical Western Atlantic, only 20% are known from other biogeographic provinces.