Evolution of reproductive strategies in the species-rich land snail subfamily Phaedusinae (Stylommatophora: Clausiliidae).

Most of the present knowledge on animal reproductive mode evolution, and possible factors driving transitions between oviparity and viviparity is based on studies on vertebrates. The species rich door snail (Clausiliidae) subfamily Phaedusinae represents a suitable and unique model for further examining parity evolution, as three different strategies, oviparity, viviparity, and the intermediate mode of embryo-retention, occur in this group. The present study reconstructs the evolution of reproductive strategies in Phaedusinae based on time-calibrated molecular phylogenetics, reproductive mode examinations and ancestral state reconstruction. Our phylogenetic analysis employing multiple mitochondrial and nuclear markers identified a well-supported clade (including the tribes Phaedusini and Serrulinini) that contains species exhibiting various reproductive strategies. This clade evolved from an oviparous most recent common ancestor according to our reconstruction. All non-oviparous taxa are confined to a highly supported subclade, coinciding with the tribe Phaedusini. Both oviparity and viviparity occur frequently in different lineages of this subclade that are not closely related. During Phaedusini diversification, multiple transitions in reproductive strategy must have taken place, which could have been promoted by a high fitness of embryo-retaining species. The evolutionary success of this group might result from the maintenance of various strategies.

Phylogeny of the land snail family Clausiliidae (Gastropoda: Pulmonata).

Clausiliidae is one of the most speciose and best-studied families of land snails. The family contributes to land snail diversity on a global scale, with three main centres of diversity: (1) western Eurasia (six subfamilies recognized), (2) East Asia (two subfamilies recognized) and (3) the neotropics (one subfamily recognized i.e. Neniinae). Despite a wealth of shell-morphological and anatomical studies, a well-supported phylogeny is lacking for the family. To provide a phylogenetic framework and reevaluate morphological and biogeographic observations on the family, we compiled a dataset consisting of partial 28S rRNA, histone H3 and histone H4 nucleotide sequences covering all clausiliid subfamilies, and 23 out of 25 tribes. Our analyses (MrBayes, BEAST, PhyML) divide the family into seven highly supported clades, which were retrieved by at least two of the three markers used, and which are more or less geographically confined. Three of these clades coincide with subfamilies recognized in the current classification (Alopiinae, Garnieriinae, Laminiferinae). The monophyly of four of the remaining six hitherto accepted subfamilies is not supported, with the New World subfamily Neniinae divided across two clades. All shell-morphological characters used in classical clausiliid classification were homoplasious at the subfamily level, with the exception of the type of shell aperture formation. In contrast to previous interpretations, our results suggest that the so-called 'apostrophic' aperture found in the neotropical clausiliids, and in a European (Laminiferinae) and a SE Asian (Garnieriinae) subfamily, is in fact the plesiomorphic condition among extant Clausiliidae. The widespread and fragmented geographic distribution of this type of aperture may therefore be considered relictual. Based on an inferred Late Cretaceous or Early Cenozoic European origin of the clade of extant Clausiliidae, the ancestor(s) of the neotropical Clausiliidae must have colonized the New World after the Atlantic Ocean had opened. A taxonomic revision is proposed.

Widespread polyphyly among Alopiinae snail genera: when phylogeny mirrors biogeography more closely than morphology.

Consider a group of species that is evenly divided by an easily identifiable complex morphological character. Most biologists would assume that this character should provide better phylogenetic information than, say, the spatial distribution of these species over a fairly continuous 500-km radius area. Paradoxically, this is not the case among terrestrial snail genera in the clausiliid subfamily Alopiinae. Phylogenetic analysis using the nuclear markers ITS1/ITS2 and mitochondrial markers COI/12S reveals widespread homoplasy in the clausilial apparatus (a complex aperture-closing mechanism), and concomitant extensive polyphyly among Carinigera, Isabellaria, and Sericata. In contrast, phylogenetic relationships as revealed by molecular data are closely congruent with biogeography at a relatively small scale. A combination of extremely low vagility and extremely high morphological convergence has conspired to produce this unexpected result. Implications as to the function of the clausilial apparatus are discussed.