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The altitudinal limit of Leptohyphes Eaton, 1882 and Lachlania Hagen, 1868 (Ephemeroptera: Leptohyphidae, Oligoneuriidae) in Ecuadorian Andes streams …

Abstract:

We explored mechanisms determining the upper altitudinal limit of ephemeropterans from two different genera: Leptohyphes Eaton, (Leptohyphidae) and Lachlania Hagen, (Oligoneuriidae). For this, we (1) surveyed the two taxa in 165 stream sites along a wide altitudinal gradient; (2) sampled benthic fauna at short altitudinal intervals along a stream, from 2780 to 3150 m above sea level; (3) collected adults at the lowest and highest sites; and (4) transplanted nymphs from the lowest to the highest study site in our stream to determine survival over time. Densities of the two taxa declined gradually with altitude and both disappeared between 2950 and 3080 m a.s.l. The upper altitudinal limit in the stream seemed to be most closely related to mean oxygen saturation, temperature, and current velocity. Adults were collected where the nymphs were found, but not at the upstream site where the nymphs were absent …