What do river snails reveal about the radiation of species?

The question of how species and thus biodiversity are created has so far mainly been modelled on vertebrates. This is despite the fact that invertebrates represent the actual diversity of species.

This project will therefore use the example of freshwater snails of the Brotia genus, which is widespread in Thailand and elsewhere, to gain insights into the mechanisms and patterns of speciation.

Our preliminary studies have shown that only one river in the mountains of Thailand, the Kaek River system, is home to a wide variety of these snails. But why are there so many different species there of all places? And how exactly did they evolve?

Together with the evolutionary biologist Walter Salzburger, RAD(restriction-site-associated DNA) sequencing is being used to analyse divergences in the genome in order to test the effectiveness of geographical barriers or other mechanisms of genetic isolation, such as those caused by environmental factors.

Freshwater snails are ideal as model organisms

Freshwater snails are suitable model organisms for researching speciation mechanisms: they have limited mobility and are therefore highly dependent on habitat conditions.

Species swarms in rivers in particular have hardly been studied to date. However, due to the geographically linear topography, they are easily accessible for studies.

Endemic freshwater snails of the genus Brotia in the Kaek River, with less than a dozen microgeographically scaled species, therefore represent an ideal model system as a natural experiment for studying basic speciation mechanisms and influencing factors.

Genetic and morphological analysis come together

For this project, we combine morphological adaptations with genetic data in order to assess the existence of an original riverine radiation. To this end, we are testing the hypothesis of spatially correlated differentiation against the background of ecological parameters such as habitat and substrate preferences.

The modelled study thus allows us to assess the influence of external factors on the development of biodiversity. At the same time, it provides the necessary data basis for estimating the contribution of possible internal causes of the speciation process.

This is being investigated further in an associated doctoral project. Using the example of Brotia species, the evolution and speciation in a river system will be modelled in the Kaek River.

PhD project: "Testing a riverine radiation - Mechanism of speciation in viviparous freshwater gastropods endemic to the Kaek River, Thailand", Nora Lentge-Maaß (2019)