Southeast Asia is due to its richness in species one of the “hot spots” of biodiversity. This comprises not only terrestrial and marine organisms but also limnic groups, such as e.g. the Gastropoda among the Mollusca, one of the largest phyla of animals second only to the arthropoda (insects, crustacean etc.). However, following the initial discoveries and the descriptions of new taxa and species found in Southeast Asia since the 19th century and surveys in the course of WHO activities for protection against human diseases, in particular Schistosomiasis, in the 1960s, research focussing on limnic gastropods has continuously decreased. Notable exceptions to this are the interest of parasitologists studying gastropods as intermediate hosts in the course of several infection’s life cycle (e.g. work done by D. Krailas in Thailand). Only recently a renewed interest came from evolutionary biologists and systematists, focussing on limnic taxa as model system e.g. for speciation and biogeography studies (e.g. work done by M. Glaubrecht and others).
Biodiversity in this context is understood as not only species diversity (or taxonomic disparity) of organisms from different (in this case limnic) environments, but also the genetic diversity within individual taxa (i.e. here in particular species). Accordingly, based on an organismic, i.e. comprehensive holistic approach using representative samples of individual populations in the field (within a naturally evolving geographical framework), we here suggest to study the phenotypic, genetic and ecological diversity using limnic gastropods as exemplar model system. In this context we plan to focus on the taxonomic and genetic diversity of selected limnic gastropods (although other taxa will also be collected in the field and deposited in museum collections for further studies).
We suggest among the Cerithiodea, a basal, ecologically and phylogenetically most important, essentially marine Caenogastropoda group, to focus on the family Thiaridae. This group represents, as became evident in recent studies (Glaubrecht 1996; Lydeardy et al. 2002; Strong et al. 2010), one of the two (or three) independent invasions into and colonizations of freshwater habitats, and which are mainly distributed in Southeast Asia having an importance as intermediate hosts for infections in humans.
Within the Thiaridae we plan to focus on two genera, viz. Melanoides and Thiara which are widely distributed with many congeneric species and constituent populations both in Thailand and in SE Asia. They are described as being phenotypically highly polymorphic and known, due to most recent preliminary molecular studies, to be genetically diverse.
Our aim is, based on a most comprehensive survey and collections from various regions, drainage systems and locations essentially in Thailand (with reference to extralimital locations), to characterize the phenotypical and especially the genetical diversity, disparity and variability.
We will use conchological parameters (shell biometry), radula morphology (scanning electron microscopy), reproductive strategy (number and embryonic stages of the brood in these viviparous snails), and parasitic infections in concern with mitochondrial gene sequencing (16S and COI gene fragments of about 900 and 600 bp, respectively, with known primers developed for thiarids in our lab in Berlin).
This will provide the data basis for various phylogenetical and phylogeographical analyses using standard algorithms and program packages (MP, ML, NJ and Bayesian analyses).