Hypervariable or Hyperdiverse, an Independent Assessment of the Taxonomically Confusing Land Snail Genus Tropidophora (Pomatiidae: Littorinoidea: Caenogastropoda) in Madagascar*

Abstract: The terrestrial littorinoid snail genus Tropidophora Troschel, 1847 is especially diverse on Madagascar with 94 currently recognized species and numerous named varieties. Supposed high within-species variation in shell and genital morphology led some researchers to suggest that these characters may be too variable to distinguish species, prompting them to conclude that the group may be taxonomically over-split. Recent sampling allows an independent test using COI sequence data which suggests that Madagascar's Tropidophora species are not over-named but are more diverse than previously thought. Molecular diversity is congruent with traditional morphology-based species concepts suggesting that future work using both molecular and morphological data sets will be useful in a taxonomic revision of the genus.