Altitudinal patterns of Diptera richness and density in streams: a scientometric approach.

Environmental changes along altitudinal gradients strongly influence the distribution of aquatic insects. We conducted a scientometric review to assess the impact of altitude on Diptera communities, with a particular focus on Chironomidae and Simuliidae. Articles published until 2025 were retrieved from Scopus, Web of Science, and SciELO using multilingual (English, Spanish, and Portuguese) search strings combining insect groups (Diptera, Chironomidae, or Simuliidae), altitudinal terms (altitude or elevation), and freshwater habitat descriptors (river, stream, lotic, or freshwater). After screening 2,304 articles, 88 met the selection criteria. Most publications originated from South America, particularly Argentina and Brazil. Across 739 streams, Diptera showed no significant relationship between altitude and richness (family, genus, or species level) or density. Similarly, analyses of 345 streams indicated no clear altitudinal pattern for Chironomidae richness or density. In 455 streams, Simuliidae exhibited significant declines in species and subgenus richness with increasing elevation, whereas genus richness and density showed no clear altitudinal pattern. Despite regional advances, research on Diptera along altitudinal gradients remains scarce and fragmented. Expanding studies on these key insect groups is essential to improve understanding of their ecological responses to environmental change in mountain ecosystems.