Abstract
The taxonomy of southeast Asian gastrocoptine pupillid micro land snails is based almost entirely on shell morphological characters, with an emphasis on apertural barriers. We aimed to test the phylogenetic utility of these characters by constructing a molecular phylogeny, based on nuclear (28S rDNA) and mitochondrial (16S rDNA) ribosomal gene fragments, for a cross-section of Thai gastrocoptine diversity (15 species). Although characterized by high levels of genetic differentiation and homoplasy, our molecular dataset provided a number of novel insights into gastrocoptine evolution and systematics. Nominal conspecifics of three genera with replicate samples (Gyliotrachela, Hypselostoma and Anauchen) occupied contiguous sections of treespace; however, all three were paraphyletic. Two inferred examples of reductive loss in apertural lamellae were encountered: Aulacospira smaesarensis was firmly nested within an otherwise exclusively Gyliotrachela tip clade; the leaf-litter-dwelling Hypselostoma panhai exhibited striking conchological differentiation from its geographically proximate rock-dwelling sister taxon H. erawan. Our results caution against the unquestioned use of apertural dentition characteristics as diagnostic generic characters, imply that ecological transitions can lead to rapid morphological change, and suggest that a comprehensive sampling of both rock and leaf-litter lineages is required to fully flesh out phylogenetic relationships among regional pupillid microsnails. Our findings also emphasize the utility of geographically proximate gastrocoptine taxa to establishing sister relationships for locally endemic species, irrespective of apparent morphological similarity. However, not all Thai gastrocoptines have localized ranges; Krobylos maehongsonensis has apparently experienced geographically extensive patterns of gene flow and colonization.
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