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The Distribution and Ecology of the Terrestrial Shell-Bearing Mollusca of Hanover, Henrico, and Chesterfield Counties, Virginia" (1954)

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The Distribution and Ecology of the Terrestrial Shell-Bearing Mollusca of Hanover, Henrico, and Chesterfield Counties, Virginia University of Richmond UR Scholarship Repository Master's Theses Student Research 4-1-1954 The distribution and ecology of the terrestrial shell- bearing mollusca of Hanover, Henrico, and Chesterfield counties, Virginia John Bayard Burch Follow this and additional works at: http://scholarship.richmond.edu/masters-theses Recommended Citation Burch, John Bayard, "The distribution and ecology of the terrestrial shell-bearing mollusca of Hanover, Henrico, and Chesterfield counties, Virginia" (1954). Master's Theses. Paper 90. This Thesis is brought to you for free and open access by the Student Research at UR Scholarship Repository. It has been accepted for inclusion in Master's Theses by an authorized administrator of UR Scholarship Repository. For more information, please contact [email protected]. THE DISTRIBUTION AND ECOLOGY OF THE TERRESTRIAL SHELL-BEARING MOLLUSCA OF HANOVER, HENRICO, AND CHESTERFIELD COUNTIES, VIRGINIA by John Bayard Burch LIBRARY · UNIVERSlT"f OF R\CHMONO · VIRGINIA A Thesis Presented to the Graduate School of the University of Richmond in Partial Fulfillment of the Requirements for the Degree of Master of Science University of Richmond June, 1954 ACKNOWLEDGEMENTS To the many individuals who have made the completion of this thesis possible, I wish to express my sincere appreciation. I am especially grateful to Dr. Nolan E. Rice, who directed the research, and to Dr. Robert F. Smart, for his help and assistance and in making possible my study at the University of Richmond. Grateful acknowledge­ ment is also made to Dr. John c. Strickland for his invaluable advice and criticism, and to the other members of the staff to the Department of Biology for the many considerations they have shown. It is a pleasure to acknowledge the aid of Dr. Henry A. Pilsbry, Olrator of Mollusks, Academy of Natural Sciences of Philadelphia, Dr. ~:J. P. E.,,Morrison, Associate Olrator of Mollusks, u. So National Museum, and Dr. Paul R. Burch, Professor of Biology (retired), Radford College, Virginia Polytechnic Institute, for the identification of certain critical species. Acknowledgement is made to Dr. P. H. DeHart, Assistant Director, Dr. c. I. Rich, Associate Agronomist, and Mr. w. w. Lewis, Extension Agronomist, all of the Virginia Agricultural Experiment Station, Virginia Polytechnic Institute, and to Dr. Rodney c. Berry, Chief Chemist, Division of Chemistry, Department of Agriculture and Immigration, Richmond, Virginia, for analysis of and information concerning soil samples. I am indebted to Dr. A. S. Pearse, Professor Emeritus, Depart--­ ment of Zoology, Duke University, for the bibliography of his paper (Pearse, 1953) on molluscan ecology presented at the 1953 Meeting II of the Association of Southeastern Biologists. Thanks are due to Professor Charles E. Packard, Associate Professor of Biology, Randolph-Macon College, Miss Katherine Putnam of Westhampton College, and Mr. Austin Somerville, Richmond College, for the addition of many specimens to my collections. Grateful acknowledgement is made to Mr. Richard Collier and Dr. Alton D. Brashear, both of the Medical College of Virginia, and to Dr. Robert F. Smart and Mr. SaDJJel L. Cooke, of the University of Richmond, for their help in the photography of the specimens dealt with in this thesis. I am particularly indebted to the Graduate School of the University of Richmond for a William's Fellowship and the Virginia Academy of Science for a Research Grant which helped meet the financial demands of this·~ problem. III CONTENTS Page ACKNOWLEDGEMENTS••••••••••••••••••••••••••••••••••••••• II INTRODUCTION........................................... 1 MATERIALS AND METHODS. • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • • . 2 DESCRIPTION OF THE AREA ••••••••••••••••••••• ,........... 4 DISTRIBUTION OF SPECIES•••••••••••••••••••••••••••••••• 7 AN EVALUATION OF SOME ECOLOGICAL FACTORS RELATED TO THE OCCURRENCE AND DISTRIBUTION OF LAND SNAILS ••••••••••••• 18 Habitat••••••••••••••••••••••••••••••••••••••••••• 18 Plant Associations•••••••••••••••••••••••••••••••• 19 Crganic Matter.................................... 21 Inorganic Compounds ••••••••••••••••••••••••••••••• 23 Soil Type •••••••••••••••••.••••••••••••••••••••••• 27 Moisture•••••••••••••••••••••••••••••••••••••••••• 28 Hydrogen-Ion Concentration •••••••••••••••••••••••• 29 Climate ••••••••••••••••••••••••••••••••••••••••••• 31 Elevation••••••••••••••••••••••••••••••••••••••••• 32 Animal Associations and Predators ••••••••••••••••• 33 SUMMARY•••••••••••••••••••••••••••••••••••••••••••••••• 34 LITERATURE CITED••••••••••••••••••••••••••••••••••••••• 36 APPENDIX••••••••••••••••••••••••••••••••••••••••••••••• 40 A. Field Data Sheet •••••••••••••••••••••••••••••• 41 B. Map of Hanover, Henrico, and Chesterfield Counties •••••••••••••••••••••••••••••••••• 45 c. Geologic Map of Hanover, Henrico, and Chesterfield Counties ••••••••••••••••••••• 45 iv D. Map of Collecting Stations with Elevations above Sea Level•••••••••••••••••••••••••••••• 47 E. Key to Collecting Stations •••••••••••••••••••••••• 49 F. Map of Collecting Stations where Soil Analysis were Made•••••••••••••••••••••••••••••••••••• 53 G. Distribution Maps •••••••••••••••••••••••••••• ·••••• 55 H. Frequency Indexes and Frequency Percentages ••••••• 73 I. Plant Associations •••••••••••••••••••••••••••••••• 76 J. Snails Found at Stations where Soil Samples were Taken••••••••••••••••••••••••••••••••••• 79 K. Frequency of Snails from Stations where Soil Samples were taken ••••••••••••••••••••••••••• 86 L. Table and Graphs of Frequencies of Snails in Relation to pH, Calcium, Magnesium, Phosphorus, Potassium, and Organic Matter.... 88 M. Plates and Figures of Land Snail Specimens •••••••• 101 CGRAPHICAL SKETCH v INTRODUCTION Very little has been published concerning the molluscan fauna of Virginia, this being also true for the area under consideration. A preliminary list of the Mollusca of Hanover County was published by J. B. Burch (1952) in which twenty-five species and subspecies of land snails were reported. Several of the land Mollusca of Henrico and Chesterfield Counties were listed by P. R. Burch (1950). These included the snails Discus patulus Deshayes, Haplotrema concavum (Say), Mesodon thyroidus (Say), Stenotrema hirsutum (Say), Triodopsis Fallax (Say), and Ventridens =(zonitoides) arboreus (Say). Two additional species, Helicodiscus parallelus (Say) and Retinella indentata (Say), were reported by personal communication. Triodopsis obsoleta .= (Triodopsis hopetonensis obsoleta) (Pilsbry) was reported by Hubricht (1953) as being an introduced form in Richmond but specimens have not been found in the present study. Pils~y (1939-48) does not list any snails from the area dealt with here. This thesis is concerned with the land snails of the Richmond area, including Hanover~ Henrico, and Chesterfield Counties, Virginia, and centers around a study of their ecology and distribution. 1 MATERIALS AND METHODS One hundred and seventy-eight collections from one hundred and twenty-three stations have been made throughout the area between June, 1952, and November 1953. Each station is listed by number in the table of Appendix E and on the distribution maps of Appendix G with reference to the nearest u. S. or State highway. To insure adequate coverage, county roadmaps and topographical quadrangle maps were utilized. All field data were recorded on special forms (Appendix A) in the field and placed in a permanent log-book. Snails are not distributed evenly over any large area, but nearly always occur more commonly in certain situations than in others. In order to secure speciumens, the habitat preferences were first learned and then the snails were searched for in their preferred habitat. Careful observations have shown that most of the land snails hide beneath decaying logs, leaf mold, rocks, and in general under any debris that offers adequate protection against desiccation and extreme temp­ erature changes. The larger species were collected by simply turning over their protective covering and picking them off with forceps. Several forms were found beneath the bark of rotting logs. A large number of the land snails of this region are minute in size (0.5 mm. - 2.0 mm.) and are, therefore, quite difficult to collect. The smaller species were obtained by running the leaf mold and top soil through a series of sifters, graduated from four meshes per inch to thirty meshes per inch. The residues were placed in shallow dishes and examined with a hand lens o.r compound microscope. Specimens were killed in the field with seventy per cent ethyl 2 alcohol and placed in shell vials, unless they were to be used for close study of external and internal anatomy. In this case they were brought into the laboratory, anesthetized in a five per cent chloretone solution and killed in ten per cent formalin. Measure­ ments were taken by means of a vernier caliper or ocular micrometer, depending upon the size of the specimen~ Field observations show that land snails are not distributed at random. Because of this, random sampling methods were not used in studying their distribution, but random samples of soil were taken from the total number of stations in order to study the pH, organic and inorganic composition. At each station all the snails were taken from an arbitrarily selected nine square feet of habitat between May and September, 1953, the time of the year most favorable for collecting. A composite liter sample' of soil, humus, and leaf mold was taken and sent
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