Biogeography and evolutionary systematics of amphidromous snails of the genus Stenomelania (Thiaridae, Gastropoda)

Freshwater or seawater - these snails can do both

Species distribution patterns are usually analysed separately for saltwater and freshwater: Traditionally, it is assumed that freshwater species arise through spatial barriers between populations (vicariance), whereas marine species arise through wide dispersal. There is still a lack of studies relating the two processes.

The freshwater snails of the genus Stenomelania (Fischer, 1885) can be used to analyse and evaluate both: The viviparous species are adults bound to the freshwater habitats of Southeast Asia and Australasia - but they disperse as larvae via marine systems in a similar way to marine organisms.

The comparison of the genus with other groups, both marine and limnic, allows a study of the importance of intrinsic factors (such as reproductive modes) and extrinsic factors (such as habitat and geography) and their impact on speciation and dispersal processes.

A new family tree for Stenomelania

The basis for this is a contemporary taxonomic-systematic revision including modern methods. Based on this revision, the biogeography and speciation of Stenomelania will be analysed. Accordingly, the project consists of three main areas of research.

Firstly, preliminary investigations indicate a high phenotypic plasticity within the genus. Therefore, the species diversity of Stenomelania can only be accurately assessed after a thorough taxonomic revision. Molecular and morphological data must be evaluated for this purpose.

Secondly, anatomical and histological methods will be used to identify differences between species from different regions. The dispersal ability of the larvae is of particular interest. This will provide insights into the biogeography and distribution patterns of Stenomelania.

Reconstruction of historical habitats

Finally, the distribution areas of individual Stenomelania species are reconstructed on the basis of systematics and reproductive biology. In addition, the potential of transoceanic dispersal and the colonisation of geographical habitats by larval stages is discussed.

Against this background, an estimation of the spread of Stenomelania species through dispersal and vicariance can be made. Hypotheses on the historical biogeography of Southeast and Australasia will be tested, allowing conclusions to be drawn about the geological history of this region.

PhD project: "Evolutionary Systematics, reproductive biology and biogeography of Stenomelania - a viviparous freshwater thiarid gastropod with marine larvae", Benedikt Wiggering (2015-2021)