Morphological differentiation, evolutionary history and biogeography of a potential cryptic species complex of terrestrial gastropods (Cyclophorus) in Vietnam
Final Report Abstract
The limestone karst outcrops in Vietnam form terrestrial ‘islands’ for various plant and animal taxa, which depend on calcium-rich habitats. Limestone-associated organisms often occur in high abundances on karsts, while the surrounding environment isolates individual populations. These organisms are threatened as limestone is being quarried for the production of cement. One of the most conspicuous invertebrate taxa present in limestone habitats is the land snail genus Cyclophorus. Species of Cyclophorus are typically restricted to only one or very few karst areas. In Vietnam, however, one morphotype of Cyclophorus exists that is widespread in large parts of the country and has been regarded as one single species. This phenomenon could either result from a particularly widespread species, which may be far more mobile than other representatives of the genus, or from a cryptic diversity within this group. This project aimed to explore the phylogenetic and morphological diversity of potentially cryptic Cyclophorus species by focussing on material from the collections of the Natural History Museum in London. Using a phylogenetic analysis based on three marker genes, I could show that specimens sharing the widespread Cyclophorus morphotype do not form a single monophyletic group but belong to at least nine different phylogenetic lineages. Most of these lineages showed an overlap with at least one other lineage in the applied shell morphometrical analysis. All lineages show a strict allopatric geographical distribution, while they do co-occur with other Cyclophorus species with divergent shell morphologies. The pattern found in the widespread Cyclophorus morphotype has probably been caused by dispersal across karsts, followed by processes of either competitive exclusion or convergent evolution. The presence of cryptic species in this group resulted in a significant underestimation of species numbers and overestimation of distribution ranges. During my research project, I found evidence for the presence of cryptic Cyclophorus species within Vietnam’s limestone karst environments, which is of relevance for the understanding of the evolution, biogeography and distribution of this land snail genus. Furthermore, my findings increased the knowledge about the processes of development and maintenance of Vietnam’s karst biodiversity in general, which is especially of interest for conservation planning in limestone habitats.
Publications
- (2015): Phylogenetic assessment of Cyclophorus spp. (Caenogastropoda: Cyclophoridae) from Vietnam. Molluscan Forum, London, 12–13
Oheimb, K.C.M. von; Oheimb, P.V. von; Ablett J. & Naggs F.
- (2016): Community assembly among limestone karst areas – Insights from Vietnamese land snails. Molluscan Forum, London, 14
Oheimb, P.V. von; Oheimb, K.C.M. von; Ablett J. & Naggs F.
- (2016): Convergent evolution of shell shape in Cyclophorus spp. (Caenogastropoda: Cyclophoridae) from Vietnam. Molluscan Forum, London, 14
Oheimb, K.C.M. von; Oheimb, P.V. von; Ablett J. & Naggs F.
- (2016): Vietnam's biodiverse limestone karst outcrops: Do they harbour cryptic Cyclophorus species? World Congress of Malacology, Penang, 250
Oheimb, K.C.M. von; Oheimb, P.V. von; Ablett J. & Naggs F.
