Structure, biomass, and secondary production of benthic macroinvertebrates in subtropical Andean rivers.

Secondary production is the formation of heterotrophic biomass across time, which integrates several important ecological processes that affect the life of organisms, populations, communities and ecosystems, but its study has poor developed in South America. The objectives of this work were to describe the diversity of benthic macroinvertebrate assemblages in terms of abundance and biomass, and to quantify their secondary production for the first time in Andean rivers. A quantitative sampling scheme was implemented, using a Surber sampler, in three forested streams. Physical-chemical variables, nutrients, organic matter and chlorophyll were measured also. The macroinvertebrates were separated and identified mostly at the species level. Each taxon was assigned to a functional feeding group. Secondary production was estimated for 38 taxa, mostly Diptera, Trichoptera, Coleoptera, and Ephemeroptera. The annual production varied from 3769 to 13916 mg dry mass m-2 y-1. Most abundant taxa were also those with higher production, dominated by Ephemeroptera (Baetidae), Trichoptera (Hydropsychidae) and Diptera (Chironomidae and Simuliidae). Density, biomass, and production of collectors and predators were much higher than the other feeding groups. We expect that our results will be useful to evaluate the effects on stream functioning produced by global warming and other anthropogenic disturbances in our region.

A new species of Languidipes Hubbard (Ephemeroptera, Polymitarcyidae) from Borneo.

The genus Languidipes is currently represented by three species distributed in southeastern Asia, India, and Sri Lanka. Languidipes corporaali is the most widely distributed species, and both, male and female imagos, as well as nymphs, are known. In contrast, the other species, L. taprobanes and L. lithophagus, are only known from nymphs. Here, we describe a new species, Languidipes janae sp nov, based on male imagos collected from Borneo, Indonesia. This new species is characterized by the presence of ommation on mesonotum, and penis almost completely divided, with sub-quadrate base and a small outer projection basal to the long and slender distal arms. This constitutes the first record of the genus for Borneo. A cladistic analysis of the subfamily Asthenopodinae supports its taxonomic status.

Ecoregions, climate, topography, physicochemical, or a combination of all: Which criteria are the best to define river types based on abiotic variables and macroinvertebrates in neotropical rivers?

The baseline conditions for a particular river or stream type are essential to classify aquatic ecosystems based on physical and biological characteristics. In this study, we proposed a river typology for different ecoregions, climate and topography of northwestern Argentina using parameters, and combined key variables to establish reference conditions. A set of geographical, hydro-morphological, hydrological, geological (pedology and sedimentology) and physicochemical variables were measured from different rivers and analyzed with clustering and ordination techniques to develop a typology. We analyzed the correspondence of the physical river conditions and benthic macroinvertebrate assemblages using non-metric multidimensional scaling analysis, dissimilarity among assemblages, ANOSIM approach and envfit analysis in order to make an ecological validation of the classification. Our results allowed us to classify the neotropical rivers studied, according to typological systems adapted from the European Water Framework Directive. The combination of ecoregions and topography along with other variables associated (system B), was better corresponded with biological arrangements. Hence, ecoregions and topography combined turned out to be more precise as a criterion to define river types and their local abiotic and biotic reference conditions. Macroinvertebrate distribution corresponded with the classifications proposed and was related with abiotic features of the rivers. The physical variables as altitude, grain size, water temperature and turbidity were key parameters to develop a schematic model to define river types that could be implemented and tested in other countries of the region. Five river types have been identified, characterized, and included in three large groups: Mountains, Foothills, and Lowlands (Plains). Our results showed that topography and climate are two aspects that strongly influence South American freshwater biota. We propose the schematic model developed in our study as a baseline to define freshwater biomes based on altitude (topography), ecoregions (climate) and biological functional traits at a broad spatial scale (continental or global).