Defining a new autoecological trait matrix for French stream benthic diatoms

摘要

Autoecological traits of aquatic organisms are well known to provide crucial information on hydrosystems and are good complements to biotic indices for evaluating surface water ecological quality. In France, as in many other European countries, autoecological approaches concerning diatoms are based on a checklist developed in the Netherlands. While this work was pioneering and suited to the conditions of study, ecological indicators developed in such small scales and such specific natural environments often show reduced efficiency when used in other conditions.France is a vast and highly biogeographically diversified region with many situations that are not to be found in the Netherlands, such as limestone substrate rivers and torrents in mountainous areas. Consequently, the elaboration of a better suited autoecological reference system has been long requested by French water managers to support ecological diagnosis.In this study, we elaborated a new autoecological reference system gathering knowledge on environmental optima, tolerance and range values for 809 French diatom taxa, along with an ordinal classification for 7 autoecological traits: water acidity, water mineralisation, oxygen requirements, saprobity, trophic state, organic nitrogen and nitrates. By combining weighted averaging and regression tree techniques we also produced a simple, statistically robust and reproducible approach to study univariate taxa-environment relationships in a given region.This new trait matrix, in addition to providing autoecological attributes for over 200 French diatom taxa that had no correspondence in previous reference systems, also takes into account French specificities such as the scarcity of acidic situations and mineral nitrogen issues. On the basis of this new matrix, 3 autoecological functional groups have been identified in French diatom flora, mainly related to traits linked to anthropogenic disturbance. This revised autoecological classification will provide much more reliable information on French stream benthic diatoms ecology, and should therefore allow better ecological diagnosis if accompanied by rigorous management of synonyms and taxonomic levels.