Competition between the invasive macrophyte Caulerpa taxifolia and the seagrass Posidonia oceanica: contrasting strategies.

Background: Plant defense strategy is usually a result of trade-offs between growth and differentiation (i.e. Optimal Defense Theory--ODT, Growth Differentiation Balance hypothesis--GDB, Plant Apparency Theory--PAT).

Niche overlap estimates based on quantitative functional traits: a new family of non-parametric indices.

The concept of niche overlap appears in studies of the mechanisms of the maintenance of species diversity, in searches for assembly rules, and in estimation of within-community species redundancy. For plant traits measured on a continuous scale, existing indices are inadequate because they split the scale into a number of categories thus losing information. An index is easy to construct if we assume a normal distribution for each trait within a species, but this assumption is rarely true.

Functional regularity: a neglected aspect of functional diversity.

Functional diversity has been identified as a key to understanding ecosystem and community functioning. However, due to the lack of a sound definition its nature and measurement are still poorly understood. In the same way that species diversity can be split into species richness and species evenness, so functional diversity can be split into functional richness (i.

Variations in the concentration of phenolic compounds in the seagrass Posidonia oceanica under conditions of competition.

The concentration of phenolic compound was measured in the seagrass Posidonia oceanica when interacting with two Bryopsidophyceae, Caulerpa taxifolia and Caulerpa racemosa, between May 1999 and May 2000. These measurements were performed on adult and intermediate leaves and in sheaths of the seagrass. Sampling was carried out at three stations subject to increasing levels of interaction with Caulerpa.

Variations in caulerpenyne contents in Caulerpa taxifolia and Caulerpa racemosa.

Caulerpenyne (CYN) contents was measured in two Chlorophyceae algae, Caulerpa taxifolia and Caulerpa racemosa, between July 1999 and July 2000. Sampling was performed at three stations exhibiting increasing levels of competition with the seagrass Posidonia oceanica. Significant differences were observed as a function of the Caulerpa species, the season, and the level of competition.