Essays On the Pulmonates

Populations of basommatophoran pulmonate snails are common and widespread throughout American freshwaters, especially in lakes, ponds, ditches, and calmer riverine margins.  They are typically weedy in their life history adaptation, fast-growing and rapidly-spreading to colonize new habitats, with the ability to self-fertilize.

The present volume is a collection of 29 essays on pulmonate systematics and evolution, originally published in blog form between 2006 – 2018, edited and reorganized thematically.  Themes include the old tension between genetic and environmental components of morphological variance, the more recent tension between classifications based on morphology and those based on molecular tools, and the modern tension between gene trees and species trees.  An historical perspective is adopted throughout, aiming to place nineteenth and twentieth-century research into a twenty-first century context.

The Freshwater Gastropods of North America Project is a long-term, collaborative effort to survey the entire gastropod fauna inhabiting every river, lake, pond and stream in the continental United States and Canada.  Born in the summer of 1998 at the World Congress of Malacology in Washington, the effort has covered all or part of 17 eastern states to date, extending from New York to Mississippi.  In Volume 1 of this series we reported the scientific results from our survey of US Atlantic drainages from Georgia through Pennsylvania. 

The 29 essays published here in Volume 2 contain important supplementary information on the evolutionary biology of the pulmonate snails common in that vast region - 14 on the lymnaeids, 8 on the physids, 3 on the ancylids, 2 on the planorbids, and 2 on the subclass broadly considered.  Together they provide essential insight into the historical background, context, and rationale for the various methodological and taxonomic approaches advanced in Volume 1, as well as in Volume 5 on the Ohio, Cumberland, and Tennessee fauna published in 2023.

Dr. Robert T. Dillon, Jr. is America's foremost authority on freshwater gastropods. From 1983 until his retirement in 2016 he was Professor of Biology at the College of Charleston in South Carolina. He is the author of The Ecology of Freshwater Molluscs (Cambridge University Press, 2000) and over 60 scientific papers on the genetics, evolution, and ecology of snails. A former president of the American Malacological Society, Dr. Dillon wrote the freshwater gastropod chapter for the popular 2006 AMS publication, The Mollusks: A Guide to their Study, Collection and Preservation. In 1998 he founded the Freshwater Gastropods of North America Project, authoring or coauthoring an extensive website, a popular blog, and seven hardcopy volumes to date.