Biological and ecological traits of benthic freshwater macroinvertebrates:relationships and definition of groups with similar traits

1. Relating species traits to habitat characteristics can provide important insights into the structure and functioning of stream communities. However , trade-offs among species traits make it difficult to predict accurately t he functional diversity of freshwater communities. Many authors have pointe d to the value of working with groups of organisms as similar as possible i n terms of relationships among traits and have called for definition of gro ups of organisms with similar suites of attributes. 2. We used multivariate analyses to examine separately the relationships am ong 11 biological traits and among 11 ecological traits of 472 benthic macr oinvertebrate taxa (mainly general. The main objective was to demonstrate ( 1) potential trade-offs among traits; (2) the importance of the different t raits to separate systematic units or functional groupings; and (3) uniform functional groups of taxa that should allow a more effective use of macroi nvertebrate biological and ecological traits. 3. We defined eight groups and 15 subgroups according to a biological trait ordination which highlighted size (large to small), reproductive traits (K to r strategists), food (animal to plant material) and feeding habits (pre dator to scraper and/or deposit feeder) as 'significant' factors determinin g the ordination of taxa. This ordination partly preserved phylogenetic rel ationships among groups. 4. Seven ecological groups and 13 ecological subgroups included organisms w ith combinations of traits which should be successively more adequate in ha bitats from the main channel to temporary waters, and from the crenon to th e potamic sections of rivers, and to systems situated outside the river flo odplain. These gradients corresponded to a gradual shift from (1) rheophili c organisms that lived in the main channel of cold oligotrophic mountain st reams to (2) animals that preferred eutrophic habitats of still or temporar y waters in lowlands. The groups with similar ecological traits had a more diverse systematic structure than those with similar biological traits. 5. Monitoring and assessment tools for the management of water resources ar e generally more effective if they are based on a clear understanding of th e mechanisms that lead to the presence or absence of species groups in the environment. We believe that groups with similar relationships among their species traits may be useful, in developing tools that measure the function al diversity of communities.