A phylogeny of the land snails (Gastropoda: Pulmonata)

Abstract

We have undertaken the first large-scale molecular phylogenetic analysis of the Stylommatophora. Sequences of the ribosomal RNA gene-cluster were examined in 104 species of snails and slugs from 50 families, encompassing all the currently recognized major groups. It allows an independent test of the present classification based on morphology. At the level of families our molecular phylogeny closely supports the current taxonomy, but the deep branches within the tree do not. Surprisingly, a single assemblage including the families Achatinidae, Subulinidae and Streptaxidae lies near the base of the tree, forming a sister group to all remaining stylommatophorans. This primary division into 'achatinoid' and 'non-achatinoid' taxa is unexpected, and demands a radical reinterpretation of early stylommatophoran evolution. In particular, the Orthurethra appear to be relatively advanced within the 'non-achatinoid clade', and broadly equivalent to other super-familial clusters. This indicates that supposedly primitive features such as the orthurethran kidney are derived. The molecular tree also suggests that the origin of the Stylommatophora is much earlier than the main period of their diversification.

Sri Lankan snail diversity: faunal origins and future prospects

“…Within the general range of Plectopylis are several shell forms that may represent distinct genera: Endothyrella Zilch, Chersaecia Gude, Endoplon Gude, Sinieola Gude, Amphieoelina Haas, and possibly Stegodera Martens, although Stegodera is probably a camaenid (Pilsbry, 1905;Richardson, 1985). The systematic position of Craterodiseus prieei from northeastern Queensland is controversial but placement within the Corillidae on anatomical criteria (Tillier, 1989;Stanisic, 1998) or within the Camaenidae (Solem, 1973) was not supported in a molecular phylogeny where Craterodiseus came within the Limacoidea (Wade et al, 2001).…”

“…Solem (1968) hypothesised the dispersal of acavoids from a northern origin to southern Africa, Madagascar, the Seychelles, Australia and South America. This might appear untenable in the context of plate tectonic events, the basal position of acavoids within the Stylommatophora (Wade et al, 2001) and the high diversity of acavoids in the isolated land mass of Madagascar. However, because of incongruent timings between the supposed origin of taxa and plate tectonic events, the mechanism of long-distance dispersal has been restored as a more likely explanation for supposed Gondwanan distributions in many plant groups (Givnish and Renner, in press, and presentations and discussion at a Royal Society, London, meeting in March 2004, to be published).…”

“…However, in his response Solem (1981b) expressed the view that the available morphological phylogenies were unstable and unsuitable bases for rigorous analysis of distributions. With the introduction of large taxa sets F. Naggs, D. Raheem in the construction of molecular land snail phylogenetic trees (Wade et al, 2001) the formulation of hypotheses can be justified on the basis that there is an increasing capacity for critically testing them.…”

Evaluation of molecular methods for the field study of the natural history of Dicrocoelium dendriticum

“…The larger of these snails appeared to be most similar to Cernuella virgata (95-100% identity, 86.7-95.9% identity to AY014127 (Wade et al, 2001)). …”

“…The smaller snails were identified as Cochlicella acuta (99% score, 99.2-99.8% identity to AY014126 (Wade et al, 2001)). The larger of these snails appeared to be most similar to Cernuella virgata (95-100% identity, 86.7-95.9% identity to AY014127 (Wade et al, 2001)).…”