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Book details
  • Genre:SCIENCE
  • SubGenre:Life Sciences / Zoology / Invertebrates
  • Language:English
  • Series title:FWGNA
  • Series Number:6
  • Pages:324
  • Paperback ISBN:9780960084357

Yankees at The Gap, and Other Essays

by Robert T. Dillon, Jr.

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Our modern understanding of the taxonomy and systematics of the North American freshwater gastropod fauna is a function both of the natural history of the vast rivers, lakes and streams through which that diverse fauna has evolved, and the human history of the biologists who have come behind, struggling to catalog the biodiversity as it has elaborated before their eyes. Here we collect 32 essays, originally published in blog form 2019 – 2023, exploring the relationship between natural history, human history, and the evolutionary models we impose today upon the pleurocerid snails of the American interior, and upon the hydrobioid snails, broadly understood.

Featured topics include intrapopulation gene flow, barriers to dispersal, character phase disequilibrium, and speciation. Special attention is called to the phenomena of cryptic phenotypic plasticity and mitochondrial superheterogeneity, both of which were introduced in Volume 3 of the present series. Along the way we meet Professor Gerard Troost, who was twice-captured and ransomed by privateers, Captain S. S. Lyon, who singlehandly saved the Union command of George W. Morgan in 1862, and Dr. Isaac Lea, the Nestor of American Naturalists, who drives me nuts. Together these 32 studies comprise an essential companion to the scientific results of the 14-state survey of the freshwater gastropod fauna The Ohio, Cumberland, and Tennessee River systems published in Volume 5.


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.  Volume 1 (2019) in this series analyzed the results of a scientific survey of the freshwater gastropod fauna of the Atlantic drainages from Georgia through Pennsylvania, and Volume 5 (2023) extended our coverage through the Ohio, Cumberland and Tennessee drainages of the Midwest and South.

The essays collected here in Volume 6 complement and extend those published in Volume 3 on the evolutionary biology of the prosobranchs, with 20 focusing on the pleurocerid snails and 12 focusing on the hydrobioids.  Together they offer essential background to understand the context and rationale for the methodological and taxonomic approaches advanced in Volumes 1 and 5.

About the author

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 contributed the freshwater gastropod chapter to 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.