Are patterns in the taxonomic, biological and ecological traits of water beetles congruent in Mediterranean ecosystems?

1. Coleoptera species show considerable diversity in life histories and ecological strategies, which makes possible their wide distribution in freshwater habitats, including highly stressed ones such as saline or temporary waterbodies. Explaining how particular combinations of traits allow species to occupy distinctive habitats is a central question in ecology. 2. A total of 212 sites, sampled over a wide range of inland aquatic habitats in the south-eastern Iberian Peninsula, yielded 272 species belonging to 68 genera and 11 families. The affinities of genera for 11 biological and 11 ecological traits, gathered from literature and the authors own expertise, were used to assess the degree of congruence between taxonomic, biological and ecological traits. 3. Taxonomic richness was significantly related to the number of both biological and ecological trait categories, with the richest families also showing the highest functional and ecological diversity. A fuzzy correspondence analysis performed on the abundance-weighed array of biological traits separated genera according to categories of diet, feeding habits, respiration, reproduction and locomotion. A similar analysis of ecological traits revealed that preferences related to longitudinal distribution (headwater to mouth), local habitat and current velocity best discriminated genera. At the family level, there was a distinctive functional grouping of genera based on biological traits. Only Elmidae showed noticeable homogeneity across genera for both biological and ecological traits. 4. Co-inertia analysis demonstrated a significant match between biological and ecological traits (Rv-correlation = 0.35, P < 0.001). Elmidae genera displayed the highest concordance, whereas Hydraenidae demonstrated the lowest. 5. These results indicate that the predominance of habitat filtering processes in headwater streams yields biological trait conservatism (as shown by Elmidae genera), as well as trait convergence for some specific traits (for instance, respiration) among certain Dytiscidae genera and other typical rheophilic taxa, whereas other biotic factors, such as competition among species, appear more prominent in less stressed habitats. Further knowledge of traits, especially regarding physiological capabilities, is needed to better understand water beetle life history strategies.