Aquatic Diptera and their relationship with environmental variables in the lower part of the semi-arid Quilca-Chili River basin, Arequipa, Peru

Aquatic Diptera are a diverse and widely distributed group of insects globally. In Perú, knowledge about this group is limited, with existing studies focusing mainly on aquatic community ecology, water quality, and heavy metal pollution. This study aimed to analyze the composition and structure of aquatic Diptera and their relationship with environmental variables in the lower Quilca-Chili River Basin in southern Perú. Environmental variables were measured and Diptera samples were collected from 16 stations during June and October 2022. Community structure and its relationship with environmental parameters were analyzed under conditions of high and low river flow. The results revealed 13 families and 29 genera, with Chironomidae, Simuliidae, Empididae, Ceratopogonidae, Dolichopodidae, and Muscidae being the most abundant. The analysis of similarity and the non-metric multidimensional showed clear separation in dipteran composition and structure among rivers in June, while in October, only Quilca River differed significantly. The greatest variation in taxon richness between low and high flow seasons was observed in the Vitor and Quilca rivers. Diversity indices were compared across rivers and seasons using Kruskal-Wallis and Mann-Whitney tests (p<0.05). Significant differences occurred in evenness (June) and all indices (October). Among the physicochemical parameters, temperature and pH remained relatively stable across all rivers, while conductivity and total dissolved solids were consistently high. The canonical correspondence analysis indicated that in June, the abundance of Polypedilum and Forcipomyia was associated with organic matter. The genera Tabanus, Holorusia, Podonomus, Paltostoma, and Simulium were associated with dissolved oxygen. In October, Polypedilum abundance was positively related to turbidity, dissolved oxygen, salinity, and electrical conductivity, while Podonomus, Paltostoma, Tabanus, Bezzia, and Simulium were associated with river flow. These findings demonstrate that environmental variables significantly influence river conditions and determine the distribution of Diptera. This study contributes valuable insights into the aquatic Diptera communities of semi-arid river systems.