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Ancient lakes as hotspots of diversity: a morphological review of an endemic species flock of Tylomelania (Gastropoda: Cerithioidea: Pachychilidae) in the Malili lake system on Sulawesi, Indonesia

Hydrobiologia (Impact Factor: 2.21). 11/2007; 592(1):11-94. DOI: 10.1007/s10750-007-0765-8

ABSTRACT The viviparous freshwater gastropod Tylomelania (Caenogastropoda: Cerithioidea: Pachychilidae) endemic to the Indonesian island Sulawesi has radiated extensively in two
ancient lake systems. We here present the first systematic species-level review of taxa in the five lakes of the Malili lake
system, which contains the most diverse and best studied freshwater fauna on Sulawesi. Our results indicate a significantly
higher diversity of Tylomelania in these lakes than previously perceived based on morphological evidence for delimiting the taxa. We describe nine new species,
thus increasing the number of taxa known from the Malili lakes to 25. Tylomelania species are inhabiting all available substrates in the lakes, and the diversity of habitats is reflected in an unparalleled
range of radula types in this closely related group. Several species show a high intraspecific variability in some characters,
and their closer investigation will probably lead to the discovery of more cryptic species. As it is, this species flock on
Sulawesi is among the largest freshwater mollusc radiations known. Since the Malili lake system also contains other large
endemic species flocks of e.g. crustaceans and fishes, it is a major hotspot of freshwater biodiversity in Asia to become
a conservation priority.

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