Elevation transition of aquatic insects closely matches a thermal feature in the Yungas of Northwestern Argentina

Abstract

Temperature is a key factor that shapes the distribution of organisms. Having knowledge about how species respond to temperature is relevant to devise strategies for addressing the impacts of climate change. Aquatic insects are particularly vulnerable to climate change, yet there is still much to learn about their ecology and distribution. In the Yungas ecoregion of Northwestern Argentina, cold- and warm-adapted species of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are segregated by elevation. We modeled the ecological niche of South American EPT species in this region using available data and projected their potential distribution in geographic space. Species were grouped based on their ecogeographic similarity, and we analyzed their replacement pattern along elevation gradients, focusing on the ecotone where opposing thermal preferences converge. Along this interface, we identified critical points where the combined incidence of cold and warm assemblages maximizes, indicating a significant transition zone. We found that the Montane Cloud Forest holds the interface, with a particularly greater suitability at its lower boundary. The main axis of the interface runs in a N-S direction and falls between 14°C–16°C mean annual isotherms. The probability of a particular location within a basin being classified as part of the interface increases as Kira’s warmth index approaches a score around 150. Understanding the interface is critical for defining the thermal limits of species distribution and designing biomonitoring programs. Changes in the location of thermal constants related to mountainous ecotones may cause vertical displacement of aquatic insects and vegetation communities. We have recognized significant temperature thresholds that serve as indicators of suitability for the interface. As global warming is anticipated to shift these indicators, we suggest using them to monitor the imprints of climate change on mountain ecosystems.