A Study on competition between Hydrilla verticillata and Mayaca fluviatilis

Mayaca fluviatilis is an exotic ornamental aquatic introduced to the country via the ornamental aquatic plant industry. The plant is now identified as a potential invasive in the country. The plant morphologically resembles Hydrilla verticillata and, a native aquatic while growing submerged in the water. Hydrilla verticillata has been recorded for its invasive behavior in the Western Province of Sri Lanka while M. fluviatilis is still at its early stages of spread with restricted distribution. Therefore information on M. fluviatilis is lacking as it has only been recently recognized as a problematic plant. The present study was conducted with the objective of evaluating inter-specific competition between M. fluviatillis and H. verticillata. A competition experiment was designed with five treatment combinations viz. terminal shoots of M. fluviatilis only (control), terminal shoots of H. verticillata only (control) and different combinations of M. fluviatilis and H. verticillata. The experimental plots were arranged in Completely Randomized Design and plant growth parameters were recorded after eight weeks of planting. Data were analyzed by using Minitab statistical software (version 16). With the introduction of H. verticillata, all the growth parameters of M. fluviatilis were reduced of which, shoot number root number and root dry weight were significantly (p<0.05)reduced. On the other hand, with the introduction of M. fluviatilis, all the growth parameters of H. verticillata were increased of which, length of newly formed shoots, shoot dry weight and shoot number were significantly (p<0.05) increased. Therefore, due to the competition, with the introduction of M. fluviatilis, the growth performances of H. verticillata were increased. Based on the present study, in a situation where H. verticillata and both species coexist, H. verticillata will have a competitive advantage over M. fluviatilis. Hence, the result suggest that despite the similar ecology, H. verticillata may outcompete M. fluviatilis in many situations.