As thalli accumulate, the population becomes crowded and limited by the available resources. At this point, for every new thallus that appears, an existing one is shaded and dies, i.e., the population size is stable. We will study the population growth and competition of two species of floating aquatic plants, Landoltia punctata and Wolffia columbiana . Landoltia punctata is a small, non-native, floating plant which can grow into dense masses in stagnant water bodies. Landoltia usually has two leaves attached together.
Plants are solitary or with a smaller attached daughter plant.
We will be working with Wolffia columbiana , which is an average-sized member of this genus. In this experiment you will monitor the growth of lab populations of Landoltia punctata and Wolffia columbiana grown alone and in mixed cultures. You can determine the magnitude of the competitive effect of Wolffia on Landoltia by contrasting the relative rate of growth of a population of Landoltia grown in monoculture with the relative rate of growth of Landoltia grown with Wolffia . The outcome of species interactions can depend on the environmental conditions. For example, ponds in which Landoltia and Wolffia naturally occur vary in both nutrient concentration and the availability of light.