The relative importance of CSR strategies and integrative traits in explaining species dominance at local scales

Bruno H. P. Rosado & Eduardo A. de Mattos

One of the main focuses in ecology is identifying ecological strategies that describe how species cope with different environments. Most of these identifications have been based on functional traits (morphological, physiological and phenological traits related to fitness). Recently, an important and timely tool named “StrateFy” has been proposed for detecting plant strategies according to the CSR scheme, which classifies species in three main ecological strategies: competitor, stress-tolerator and ruderal. The S strategy occurs under high stress level and low intensity of disturbance. The R strategy is dominant in environments with low stress and high disturbance, where species would allocate most of their resources to growth and reproduction. The C strategy is predominant under low stress and low disturbance, where competition is intense. “StrateFy” is able to detect CSR strategies based on three leaf traits known by their ability to describe resource use and response to environmental factors: specific leaf area (leaf area/leaf dry mass, which describes leaf construction cost), leaf dry mass content and leaf area. The CSR scheme is undeniably efficient and has been proposed to explain differing degrees of dominance among species. However, in a previous study performed in a coastal sandy plain, we showed that dominance ranking of woody species in this resource-poor habitat was explained by integrative physiological traits (traits that are the final result of different combinations of morphological traits). In other words, plants that are morphologically distinct might be convergent in physiological traits, such as traits related to plant water use, which integrate different arrays of traits.

We used “StrateFy” on a dataset collected on a coastal sandy plain to test if dominance ranking would be compatible with the CSR strategies; that is, dominant species would show high values of stress-tolerance to survive in this harsh environment. Contrary to our prediction, all species showed the same strategy, more associated to S, and the most dominant species did not exhibit the highest stress-tolerance. Despite the practicality of “StrateFy”, when a given community has a narrow range of any strategy and all species have essentially the same strategy, regardless of their dominance ranking, integrative traits may be more important for explaining dominance.

Photo caption: Open Clusia scrub in the Restinga de Jurubatiba National Park. Photograph by Eduardo A. de Mattos

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