No abstract

From the early Miocene, the uplift of the Andes Mountains, intense volcanic activity and the occurrence of successive periods of dryness and humidity would have differentially influenced the modification of Altiplano watersheds, and consequently the evolutionary history of the taxa that live there. We analyzed Orestias populations from the Caquena and Lauca Altiplanic sub-basins of northern Chile to determine their genetic differentiation and relationship to their geographical distribution using mitochondrial (D-loop) and nuclear (microsatellite) molecular markers and to reconstruct its biogeographic history on these sub-basins. The results allowed reconstructing and reevaluating the evolutionary history of the genus in the area; genic diversity and differentiation together with different founding genetic groups suggest that Orestias have been spread homogeneously in the study area and would have experienced local disturbances that promoted isolation and diversification in restricted zones of their distribution.

High Andean freshwater ecosystems are highly threatened by scarce water availability, species invasion, and global climate change, so generating knowledge about their ecological characteristics is extremely important for conservation decision-making. In this work, the seasonal variations and relationships between physico-chemical variables and the structure and composition of the macroinvertebrate community were analyzed considering “season”, “type of ecosystem” and “site” factors. Five sites of representative ecosystems at Lauca River Basin of the Chilean Altiplano were sampled, two of them lentic and three lotic. Two field-sampling periods within a year according to the pre- and post-rain seasons characteristic of the Altiplano climate were considered. Thirty-five taxa were identified, and it was observed that the taxa Orthocladiinae, Austrelmis sp., Hyallela cf kochi, Podonominae and Helicopsychidae were indicator taxa that contributed the most to differences among sites or ecosystems (≥ 10 %.). No significant differences were found in the alpha diversity indicators used, except for some abundance values and Pielou’s Evenness index (J´), which varied significantly between lotic and lentic systems. The results of the ordination analysis showed a significant differentiation considering physical and chemical variables and macroinvertebrates assemblages that responded to “sites” (ANOSIM R Global = 0.64, p = 0.001) and “type of ecosystem” factors (ANOSIM R Global = 0.31, p = 0.02). The “season” factor was not statistically significant to explain the variability of biological data (ANOSIM R Global = -0.003, p = 0.47) and was slight and marginally significant with the physical and chemical data (ANOSIM R Global = 0.1, p = 0.04). In addition, the linear redundancy analysis (RDA) showed that physico-chemical variables related to hardness, temperature, phosphorous, and nitrogen explained most of the variance in the biological data (the first two canonical axes RDA1 and RDA2 explained 45.23 % of the total variation, p = 0.004). These results support the relevance of local conditions for high altitude wetlands and how those environmental characteristics can be reflected in the macroinvertebrate assemblages that inhabit them.

River basins play a critical role in ecosystem services and their status regulate the associated productivity. Anthropogenic activities along with other environmental perturbation influence the vulnerability level of that important water resource, disturbing in a short time, water quality. The aim of this work is to generate an approach to Toltén basin characterization with benthonic macroinvertebrates, physicochemical and bacterial components as indicators of variation in water quality close to human populations and the sectors furthest from them, selecting for this purpose two areas (up and downstream of the basin). We used an ANOSIM two-way analysis to relate abiotic and biotic data and for diversity and biotic index (ChBMWP) we analyzed the benthic macroinvertebrate composition. A principal component analysis for environmental variables strongly separated the analyzed zones by season as the first principal component, showing a clear increase in temperature and electrical conductivity values in spring season. Meantime the pH parameter was observed with interesting variation for longitudinal gradient with incremental values in upstream area. The biotic indexes applied to the samples between seasons reflexes a similar diversity between analyzed sites in upstream with no differences showing a low diversity of macroinvertebrates. However, a significant increase was detected during spring in downstream zone. On the other hand, Pseudomonas genus increase between the most representative microbiological genera in the basin. Our results reinforce the importance not only of frequent seasonal monitoring program but also the critical role of collecting data on total transect basin length to regulate the human activities associated to basin and to protect the water quality.