MU3. CO MP. ZOOL LIOrJARY MAR 1 8 1985 B R E V±0 R A Museum of Comparative Zoology us ISSN 00n6 9698 Cambridge. Mass. 30 November 1977 Number 445 NATURAL HISTORY OF CERION. VII. GEOGRAPHIC VARIATION OF CERION (MOLLUSCA: PULMONATA) FROM THE EASTERN END OF ITS RANGE (HISPANIOLA TO THE VIRGIN ISLANDS): COHERENT PATTERNS AND TAXONOMIC SIMPLIFICATION. Stephen Jay Gould' and Charles Paull2 Abstract. The eastern cerions (Hispaniola to the Virgin Islands) have, following the conventional practice for this diverse genus, been split into seven allopatric taxa. We reject this traditional scheme on the basis of a multivariate morphometric analy-sis ( 19 characters, 20 shells per sample) of 23 samples from all major areas of Cerion's eastern range. We first show that eastern cerions are distinct from other members of the genus by patterns of covariation among their morphometric measures. We then demonstrate by canonical analysis that populations of each island have a dis-tinct morphology. Were there no coherent patterns among islands, current nomen-clature might be supported. However, the first canonical axis (59 per cent of all information) for an analysis by islands arrays the populations in perfect geographic order— from egg-shaped, finely and copiously ribbed shells in the east, to more cylindrical, apically pointed shells with fewer, stronger ribs in the west. The mor-phological direction of this cline approaches common cerion forms further west (particularly on Cuba); unique morphologies are isolated at the eastern extreme of the range. In addition, a plot of Mahalanbbis vs. geographical distance shows a remarkably tight relationship (r = 0.96) between geographic and morphological distance. Therefore, we synonymize all living eastern cerions into the single taxon C. striatellum ("Ferrusac" Guerin-Meneville), reserving C. rude (Pfeiffer) for the rather different St. Croix fossil. I. INTRODUCTION Cerion has attracted the attention of eminent naturaHsts ever since Linnaeus designated its type species in 1758. W. H. Dal! (1905). H. A. Pilsbry (1902), P. Bartsch (1920). Ludwig Plate 'Museum of Comparative Zoology. Harvard Unncrsity. ^Rosenstiel School of Marine Science. Uni\ersit\ of Miami.
Natural history of Cerion. VII. geographic variation of Cerion (Mollusca: Pulmonata) from the eastern end of its range (Hispaniola to the Virgin Islands): coherent patterns and taxonomic simplification