Cerion: A web-based resource for Cerion research and identification
Land snails of the family Cerionidae are endemic to islands of the tropical western Atlantic. They range from the barrier islands and keys of southern Florida, throughout the Bahamas, Greater Antilles, Cayman Islands, western Virgin Islands, and the Dutch Antilles, but are absent in Jamaica, the Lesser Antilles, and coastal Central and South America. These snails live on terrestrial vegetation, usually within a few hundred meters of the shore, but occasionally a kilometer or more from the sea, in areas where salt spray can reach them. Cerion live in dense but patchy populations, often containing ten thousand or more individuals. They can be conspicuously abundant when living on open vegetation, less so when living in leaf litter. Individual populations tend to be fairly uniform in the size and morphology of their shells. Clench (1938:524) noted that the greater the isolation of the population, the greater is the uniformity among its members. Variation in shell morphology among populations can be enormous, not only throughout the geographic range of Cerion, but even among neighboring populations separated by less than 100 meters. This lavish yet geographically circumscribed diversity has led to an extensive body of literature dealing with Cerionidae. Much of the early work was primarily descriptive, and focused on parsing the various phenotypes among roughly 600 nominal species and nearly two dozen genera or subgenera. More recent research, particularly the work of Mayr, Gould, Woodruff, Goodfriend, as well as their students and collaborators addressed more basic biological questions, among them the origins as well as the geographic and temporal stability of morphological and genetic diversity, and the dynamics of hybrid zones and biogeographic patterns, both Holocene and Recent.
The fossil record of Cerion extends to the early Miocene of Florida (see Eostrophia) and possibly to the Upper Cretaceous of Montana (see Cerion acherontis), although records older than of Pleistocene age are very rare. The greatest diversity of Cerion occurs on Cuba and in the islands of the Bahamas. However, it should be remembered that most the present range of the genus, including southern Florida and many of the Bahamian Islands were submerged as recently as the Eemian interglacial era (125,000 years before present), and have been recolonized since that time.
Many researchers have conjectured that perhaps only 10-20% of the species named within Cerionidae will eventually be found to represent valid species, the rest may be subspecies, demes or merely distinctive combinations of alleles. Although Gould and Paull (1978) reduced the 11 described species from Hispanola to the Virgin Island to a single species using multivariate analyses of shell characters, they reported that 95% of the specimens could be sorted to their source populations using this data.
Cerion are remarkably well suited to studies on many aspects of evolution, population genetics, parapatric and allopatric differentiation.
The purpose of this website is to facilitate such studies by providing taxonomic, biogeographic and bibliographic information about the family Cerionidae. Included is a searchable database of all taxa proposed within the family Cerionidae. Entries for species level taxa provide an abbreviated synonymy that is linked to the bibliography, the text [and if needed an English translation] of the original description, five views of the primary type specimen, as well as information on the type locality and distribution. Also included are links that will enable the user to search the holdings of major museums, and GenBank.
Geographical search features allow the user to examine and identify the named taxa from each island from which Cerion has been reported either by selecting from a list of islands of through the use of a map. A comprehensive bibliography of the Cerionidae is also included.
This website is still a work in progress. Comments, corrections, suggestions and additional data on Cerion may be sent to: Harasewych@si.edu
This research was supported in part by the National Science Foundation under grant # EAR 0106936 to S. J. Gould, G. Goodfriend and M. G. Harasewych. This site is hosted by the National Museum of Natural History, Smithsonian Institution and edited by M. G. Harasewych and Y. Villacampa.
Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.