Abstract:
Streams are one of the main aquatic ecosystems which have a connectivity form head waters to
oceans. Along this longitudinal gradient, streams exhibit huge faunal and floral diversity. Despite
the well-observed variations with in the same floral species along the streams; information on
factors behind such variations is scarce to our knowledge. Thus, the present study was designed
to study the factors behind the observed morphological variations in Aponogeton crispus
(Kekatiya in Sinhala) found in the Dediyagala stream located in Matara district. Five study sites
were selected along a segment (~2 km) of the stream. For each site, plant density was detected in
randomly selected quadrate (50×50 cm2) and plants were sampled for the subsequent
morphological, anatomical, biochemical and genetic analysis. Physichochemical properties such
as pH, temperature, and dissolved oxygen content, water flow velocity and conductivity of water
were measured onsite while nutrients (NO3
- and PO4
3- concentration in water and soil) was
measured at the laboratory. Sediment core samples were brought to detect organic matter content
and the particle size distribution. Molecular identification of selected plant samples was
performed by DNA barcoding. Morphological variations such as length, width folds of plant
leaves were observed and they significantly correlated to the abiotic factors including velocity,
plant density, particle size, soil nitrate, water nitrate, dissolved oxygen, pH, and total suspended
solids. However, irrespective of the observed morphological variations in the selected plants, the
molecular composition of the DNA barcoding regions namely, MatK and psbA-trnH of the
selected plants were found to be the same as wild type plant Apanogetton crispus. This was
further confirmed by the phylogenetic tree analysis. Therefore, this study revealed that the
morphological variations in Aponogeton crispus can be attributed to the function of abiotic
factors. Together with these finding further studies on other factors that may influence the
morphology variance and DNA barcode for another primers could assist better understanding
and management of aquatic ecosystem.
