Testing allopatric and ecological speciation in a morphologically and genetically diverse species flock of viviparous freshwater gastropods (Mollusca: Cerithioidea: Pachychilidae) in the ancient lakes of Sulawesi, Indonesia

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Speciation in the context of a radiation is regarded as a key process in the creation of organismic diversity. Adaptive radiations in lakes provide almost perfect conditions to study the ecology of speciation, with freshwater gastropods being ideal model organisms. The ancient Malili lakes on Sulawesi, Indonesia, harbour an endemic species flock of about 16 species of viviparous freshwater snails. These snails show not only a high degree of inter- and intraspecific morphological differentiation, but also of molecular divergence. A mtDNA based molecular phylogeny reveals several old lineages which independently colonized the lakes, and within each clade bursts of very recent radiation with unresolved relationships on the population and species level. The rates of molecular and morphological evolution have been found to be highly divergent in lake species as opposed to widespread riverine taxa, pointing to strong selective pressures on certain traits associated with transition to a lacustrine environment and habitat use within the lakes. The proposed study therefore aims to test various alternative hypotheses of speciation factors and processes relevant for the evolution of the lake gastropod diversity in space by (1) uncovering patterns of gene flow and genealogical relationships within and among key populations of major clades and (2) getting base-line data on ecological differentiation for these populations in order to (3) quantify phenotype-environment correlations and (4) evaluate trait utility. The emerging speciation pattern for the gastropods shall be tested for congruence with those gained - in a cooperative approach with other researchers - from endemic fishes and crabs.