Ephemeroptera Along Altitudinal Gradients: a Scientometric Review

Altitude is a key environmental factor influencing ecological patterns and biodiversity in ecosystems. In aquatic organisms, taxonomic richness typically declines with increasing altitude, although studies on Ephemeroptera show variability in this trend. To better understand this relationship and identify research gaps, we conducted a literature review using the Web of Science database using the terms "Ephemeroptera", "Mayfl*", "watercourse" and "altitude" in English, Portuguese, and Spanish, complemented with data from a global study on aquatic insects. Out of 228 identified articles, 74 met our criteria. The most relevant journals were Freshwater Biology (n = 11) and Hydrobiologia (n = 5). Studies were concentrated in the Palearctic (40.5%) and Neotropical (29.7%) regions, with Algeria (n = 6), Slovakia (n = 4), Ecuador (n = 8), and Argentina (n = 8) as the most studied countries. Most studies investigated the influence of environmental factors on community composition and diversity (n = 35). Only ~30% focused exclusively on Ephemeroptera, emphasizing nymph stages and species-level taxonomy. Sampling was concentrated at up to 20 sites (n = 42) at elevations below 3,000 m. Our analysis confirms that Ephemeroptera species richness, genus richness, and overall abundance significantly decline at higher elevations.