The influence of environmental variables on bdelloid rotifers of the genus Rotaria in Thailand

This research investigates the influence of environmental parameters that are known to affect bdelloid rotifer species richness and composition in temperate zones on the genus Rotaria in tropical zone. Our study analysed species richness and composition of the genus Rotaria from 390 samples collected from several types of aquatic habitats in Thailand. Coordinates, elevation, limnological parameters such as water temperature, conductivity, total dissolved solids, salinity, dissolved oxygen and pH were measured. A total of nine species was recorded. Of these, one species, Rotaria macrura (Ehrenberg, 1832), was a new record for Thailand and new to the oriental region, and was a yet undescribed species, Rotaria sp. The species diversity of this genus increased from eight to 10 species. The presence or absence of the genus Rotaria was significantly influenced by dissolved oxygen and habitat type. For the samples where the genus occurred, species richness was not affected by any of the limnological or bioclimatic variables. Differences in species composition were affected only by habitat type. The results support former suggestions that common abiotic parameters do not seem to strongly influence diversity in bdelloids, whereas major ecological differences between habitats influence bdelloid occurrence.