, Volume 579, Issue 1, pp 317–335 | Cite as

Genetic and morphologic variation of the Pecos assiminea, an endangered mollusk of the Rio Grande region, United States and Mexico (Caenogastropoda: Rissooidea: Assimineidae)

  • Robert Hershler
  • Hsiu-Ping Liu
  • B. K. Lang
Primary Research Paper


Assiminea pecos is an endangered species of amphibious gastropod that occupies four widely separated portions of the Rio Grande region in the southwestern United States (Pecos River basin) and northeastern Mexico (Cuatro Cienegas basin). Our statistical and discriminant function analyses of shell variation among the disjunct populations of this species indicate that Mexican specimens differ in their morphometry from those of the United States and can be diagnosed by several characters. We also analyzed variation in the mitochondrial genome by sequencing 658 bp of mitochondrial COI from populations of A. pecos, representatives of the other three North American species of Assiminea, and several outgroups. Our results indicated substantial divergence of the Mexican population of A. pecos, which was consistently depicted as a monophyletic unit nested within or sister to the shallowly structured group comprised of American members of this species. Consistent with our findings, we describe the Mexican population as a new species, which is provisionally placed in the large, worldwide genus Assiminea pending further study of the phylogentic relationships of the North American assimineids. Our molecular data suggest that the Rio Grande region assimineids, which are among the few inland members of the otherwise estuarine subfamily Assimineinae, diverged from coastal progenitors in the late Miocene, with subsequent Pleistocene vicariance of Mexican and American species perhaps associated with development of the modern, lower course of the Rio Grande.


Assiminea Gastropoda North America Systematics Biogeography Conservation 



The following individuals collected material used in this study and/or assisted with our fieldwork—N. Allan, L. L. Crisostomo, V. Gervasio, M. E. Gordon, T. Hyde, M. G. Kellogg, S. Knapp, J. J. Landye, A. L. Metcalf, L. Manning, F. G. Thompson, C.-l. Tsai, and S.-K. Wu. Scanning electron microscopy and shell measurements were performed by Y. Villacampa. K. Darrow and M. K. Ryan assisted with preparation of the map and specimen drawings, and D. Barrett kindly wrote a Perl Script that eased data file conversion. Tom Quinn (University of Denver) and Sara Oyler-McCance (United States Geological Survey) generously shared bench space and equipment in the Rocky Mountain Center for Conservation Genetics and Systematics. The first author’s fieldwork was supported, in part, by contract funds provided by the United States Fish and Wildlife Service (Region 2) and the State of New Mexico. Permission to collect on Nature Conservancy land in Texas was authorized by John Karges. This paper benefited from comments provided by Martin Haase and an anonymous reviewer.


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Copyright information

© Springer Science+Business Media B.V. 2007

Authors and Affiliations

  1. 1.Department of Invertebrate ZoologySmithsonian InstitutionWashingtonUSA
  2. 2.Department of Biological SciencesUniversity of DenverDenverUSA
  3. 3.New Mexico Department of Game and FishSanta FeUSA

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