Convergent evolution of Amphidromus-like colourful arboreal snails and phylogenetic relationship of East Asian camaenids, with description of a new Aegistohadra species (Helicoidei: Camaenidae: Bradybaeninae)

Abstract

Abstract East Asian terrestrial snails of the family Camaenidae Pilsbry, 1895a are diverse in terms of genus and species numbers, shell morphology and mode of living. This family also includes colourful conical arboreal snails that traditionally have been assigned to the genus Amphidromus Albers, 1850. Yet, the present study shows that, despite their deceiving conchological similarity, some of these East Asian arboreal snails do not belong to the genus Amphidromus or the subfamily Camaeninae Pilsbry, 1895a. The presence of a dart complex comprising a mucous gland, a dart sac, an accessory sac and a proximal accessory sac, along with a pronounced penial caecum and molecular phylogenetic analyses revealed that former ‘Amphidromus’ dautzenbergi, ‘A.’ roemeri and ‘Camaena’ mirifica, and one additional new species belong to Aegistohadra Wu, 2004 (subfamily Bradybaeninae Pilsbry, 1934). Aegistohadra dautzenbergi, comb. nov. and Aegistohadra roemeri, comb. nov. are conical with colourful spiral bands, whereas Aegistohadra mirifica, comb. nov. and Aegistohadra zhangdanae, sp. nov. are heliciform to conical with colourful, variegated spiral and transverse banding patterns. DNA sequence analyses also revealed that each variety of Aegistohadra dautzenbergi could not be differentiated by mitochondrial (cytochrome c oxidase subunit I and 16S rRNA) gene fragments. The phylogenetic position of Aegistohadra within the East Asian camaenids revealed that the similar appearance in shell morphology, microhabitat use and diet to arboreal snails in the genus Amphidromus is homoplastic. Moreover, the presence or absence of a dart complex is also homoplastic and is unsuitable for suprageneric classification. By contrast, the presence of a flagellum and a penial caecum is useful for the suprageneric classification.