One of the biological indicators most used to determine the health of a fluvial ecosystem are the benthic macroinvertebrates. The presence of recurrent species in a wide gradient of latitudes, dominates the biogeographic pattern of the benthic macroinvertebrates in Chilean fresh waters, nevertheless the knowledge on the communitarian ecology of these in the Chilean rivers continues to be scarce. Null models became a powerful statistical tool for describing the ecological mechanisms that drive the structure of an ecological community and the underlying patterns of diversity. The objective of this study was to determine the community structure of benthic invertebrates in the Allipén River by describing their composition, richness and abundance of species through richness models and null models based on presence/absence. The results reveal a high family richness and low diversity, three phyla, five classes, 11 orders and 28 families were identified in the study area during the four seasons of the year. The Arthropoda phylum was the most representative in abundance and richness. Regarding to richness, Trichoptera (7 families) and Diptera (6 families) followed by Ephemeroptera (3 families) were the orders that showed the greatest diversity of families, however, a low diversity with a H’≤ 1.5 nit was registered in the study area. We demonstrated through the null models, the randomization in the species associations corresponding to the three analyzed sites. The information provided here contributes to the understanding of the ecological patterns of the invertebrate communities in the Allipén River, establishing the basis for more complex ecological studies.

The freshwater anomuran crabs of the genus Aegla are widespread throughout lakes and rivers in central and southern Chile. They form an important component of the benthic fauna, because the species of the genus are shredders of organic debris and also make an important prey for native and introduced fishes. Nevertheless, the ecology of this genus has been poorly studied in lakes in comparison to rivers. The aim of the present study was a description of the spatial pattern of distribution of an Aegla rostrata population from the littoral zone of Pullinque Lake, in the north of Chilean Patagonia. The results revealed a low density (1.0 ± 0.8 ind/m2), that had a uniform pattern, and has a positive binomial distribution. The results would indicate that the studied species would have territorial behaviour that would be associated with interspecific resource competition. The observed results would agree with observations for the benthic zones in Chilean Patagonian lakes, where Aegla would show territorial behaviour.

The crustacean zooplankton in Chilean Patagonian lakes is characterized by a marked dominance of calanoid copepods when under an oligotrophic status. The aim of the present study was to analyse the number of eggs and the relation of that feature with the total length of females of calanoid and cyclopoid copepods reported in three northern Chilean Patagonian lakes. The calanoid copepods found were Boeckella gracilipes in Lake Pellaifa and Tumeodiaptomus diabolicus in the lakes Panguipulli and Calafquén, whereas the cyclopoid Mesocyclops araucanus was found in the lakes Pellaifa and Calafquén. For calanoid copepods, high egg numbers were found and thus also a high value for the ratio of egg number per female length in Lake Panguipulli, whereas for M. araucanus a high value was found in Lake Pellaifa. These differences would presumably be associated with community structure, specifically predator-prey relationships and possibly other interactions, as, e.g., potential interspecific competition.

The northern Patagonian lakes (38-41°S), are characterized by their location in catchment basins that have been markedly altered through human intervention. In those basins, the original native, perennial forest has been replaced by towns, villages and agricultural zones. The present study was done in two interconnected north Patagonian lakes (the lakes Calafquén and Pellaifa), where the species composition of the crustacean zooplankton community was compared, using a biodiversity index and size-structure null models. The results denoted the presence of marked differences between both sites, Calafquén lake being inhabited by less species and in general showing lower abundances of individuals in comparison to Pellaifa lake. The results of size-structure null models revealed the absence of interspecific competition for both sites. The obtained results would agree with similar observations for other northern Patagonian lakes in Argentina and Chile.