Life history and ecology of the Maghrebian endemic Choroterpes atlas Soldán & Thomas, 1983 (Ephemeroptera: Leptophlebiidae)

Abstract Knowledge of the basic life history traits of an aquatic organism such as voltinism and growth patterns is a fundamental step in understanding its potential use as indicator taxon and how it adapts to its complex environment. The distribution and life cycle of the Maghrebian endemic Choroterpes atlas Soldan & Thomas, 1983 was studied over a two year period. Random forest classification indicated that the species occupied both permanent and intermittent streams with high water depth, large river bed width and strong water flow. Density-based clustering of body measurements allowed the identification of last-instar nymphs which exhibited a significant sexual dimorphism: F-0 females were significantly larger than corresponding males. In addition, size-frequency plots and generalized additive models indicated that C. atlas exhibited a multivoltine annual cycle with three overlapping generations. Nymphal growth of the first generation happened in winter and spring with emergence occurring in June/July. The second generation grew from June/July to September whereas the third generation was completed from August/September to November. GAMs also indicated that body size varied significantly between years. The large regional distribution, habitat requirement, and phenology of C. atlas may ideally complement the potential use of Ecdyonurus rothschildi as a useful environmental indicator for North African streams and rivers.