Biological traits of macroinvertebrates from subtropical streams: patterns along spatial-temporal environmental gradients

Abstract

Biological traits reflect the tactics of organisms in response to environmental change. We analysed the functional organization of the EPT group (Ephemeroptera, Plecoptera and Trichoptera) at a subtropical mountain basin to assess whether their biological traits are associated with spatio-temporal patterns in environmental variation, and whether human activity modify the functional organization of communities. Between 2005 and 2007, we sampled eleven streams during two consecutive hydrological periods of high and low discharge. We defined ten biological traits at the genus level, including aspects of: morphology (maximum size, body shape and flexibility, hardness of the exoskeleton), physiology (oxygen deficit tolerance, type of respiration and shape of gills) and behaviour (locomotion, feeding habits, specific adaptations to flow constraints). An RLQ analysis allowed the linking of habitat characteristics and biological traits, through an abundance table. Altitudinal levels along with flow regimes define spatial-temporal “Habitat Templets”. Body size, feeding habits, respiration and tolerance to oxygen deficit were the features most associated with the environmental gradient detected. High-altitude sites that show marginal vegetation, high stream power and well oxygenated waters are inhabited by filterers, scrapers and predators with tegumentary respiration and low tolerance to oxygen deficit. Low-altitude sites exhibit high conductivity, modification of the riparian forest, agricultural use, high runoff, sediment transport and reduced oxygen concentration. These sites are characterized by organisms of small size, collectors, with gills and high tolerance to oxygen deficit. These results allow us to project a framework for monitoring functional changes of the system through the EPT group.