PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 116(3):649-660. 2003. A systematic review of the land snail Euglandina singleyana (Binney, 1892) (MoUusca: Gastropoda: Spiraxidae) Kathryn E. Perez and Ned E. Strenth (KEP) Department of Biological Sciences, Box 870345, University of Alabama, Tuscaloosa, Alabama 35487; (NES) Department of Biology, Angelo State University, San Angelo, Texas 76909 Abstract. — A systematic review of Euglandina singleyana was undertaken to thoroughly examine shell morphology, allozyme, and mtDNA variation in specimens of E. singleyana endemic to central Texas. Allozyme similarity ranged from 95% in the most geographically proximal individuals of E. sin-gleyana (Val Verde and Real counties) to 82% between the most distant indi-viduals (Comal and Val Verde counties). DNA sequence similarity, based on a 397 bp partial 16S mtDNA sequence, ranged from 98% in eastern specimens (Comal and Kerr counties) to 95% in individuals from Kerr, Real, and Val Verde counties. Analysis of variation in shell morphology, allozyme similarity, and mtDNA sequences supports the existence of a single, highly variable, wide-spread species of Euglandina in central Texas. This study also examines the validity of E. immemorata, using morphometric and DNA sequence data and E. exesa, using morphometric data. The morphometric analysis showed that E. immemorata and E. singleyana differ significantly in shape. The current status of E. immemorata and E. exesa are also examined. Euglandina singleyana (Binney, 1892) is found in a wide variety of habitats along the southern margin of the Edwards Plateau in Texas, from Terrell County in the west to Fayette County in the east, and south to Refugio County (Fig. 1; Singley 1893, Pils-bry 1946, Fullington & Pratt 1974, Hu-bricht 1985). In the eastern part of its range it is found under rocks and logs in wooded stream valleys in the limestone of the Ed-wards Plateau. In the clay and sandy areas of the Balcones Escarpment, it is restricted to wooded lowlands. The range of this spe-cies extends to the western Stockton Pla-teau where it is found under fallen Yucca and in rock crevices in desert shrub habitat dominated by Lechuguilla cactus (Fulling-ton & Pratt 1974). A great deal of the historical taxonomic confusion regarding this species appears to be related to its relatively wide geographi-cal range of —250 km, compared to the me-dian range of land snail distribution of 50 km reported by Solem (1984) and high lev-el of variation in shell morphology. Shells collected in the eastern part of the range can readily be distinguished from those collect-ed in the western part of the range. One purpose of this study was to examine vari-ation in shell morphology of specimens from throughout the range of the species in central Texas to determine if there are dis-tinct differences in western versus eastern shell morphology or if there is continuous (clinal) change in shell shape and size across the range of the species. The purpose of this study was also to examine allozyme and DNA sequence variation in individuals from across the range of the species (Co-mal, Kerr, Real, and Val Verde counties) to determine if specimens conforming to the description of E. singleyana formed a monophyletic group. This study addresses the taxonomy of this species from a phy-
BioStor
