title: Comparing the efficacy of morphologic and DNA-based taxonomy in the freshwater gastropod genus Radix (Basommatophora, Pulmonata).
abstract: BACKGROUND
  Reliable taxonomic identification at the species level is the basis for many biological disciplines. In order to distinguish species, it is necessary that taxonomic characters allow for the separation of individuals into recognisable, homogeneous groups that differ from other such groups in a consistent way. We compared here the suitability and efficacy of traditionally used shell morphology and DNA-based methods to distinguish among species of the freshwater snail genus Radix (Basommatophora, Pulmonata).
  
  
  RESULTS
  Morphometric analysis showed that shell shape was unsuitable to define homogeneous, recognisable entities, because the variation was continuous. On the other hand, the Molecularly defined Operational Taxonomic Units (MOTU), inferred from mitochondrial COI sequence variation, proved to be congruent with biological species, inferred from geographic distribution patterns, congruence with nuclear markers and crossing experiments. Moreover, it could be shown that the phenotypically plastic shell variation is mostly determined by the environmental conditions experienced.
  
  
  CONCLUSIONS
  Contrary to DNA-taxonomy, shell morphology was not suitable for delimiting and recognising species in Radix. As the situation encountered here seems to be widespread in invertebrates, we propose DNA-taxonomy as a reliable, comparable, and objective means for species identification in biological research.
authors.affiliation: Abteilung Okologie & Evolution, J.W. Goethe-Universität, BioCampus Siesmayerstrasse, 60054 Frankfurt/Main, Germany. Pfenninger@bio.uni-frankfurt.de
authors.forename: Markus
authors.initials: M
authors.lastname: Pfenninger
authors.forename: Mathilde
authors.initials: M
authors.lastname: Cordellier
authors.forename: Bruno
authors.initials: B
authors.lastname: Streit
mesh_terms: D000818:Animals; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D003576:Electron Transport Complex IV / Q000235:genetics*; D005060:Europe; D005843:Geography; D008969:Molecular Sequence Data; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012908:Snails / Q000033:anatomy & histology / Q000145:classification / Q000235:genetics*
chemical_list: D004272:DNA, Mitochondrial; D021903:DNA, Ribosomal Spacer; D003576:Electron Transport Complex IV