The altitudinal limit of Leptohyphes Eaton, 1882 and Lachlania Hagen, 1868 (Ephemeroptera:Leptohyphidae, Oligoneuriidae) in Ecuadorian Andes streams: searching for mechanisms.
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Date
16/03/2016
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Abstract
We explored mechanisms determining the upper altitudinal limit of
ephemeropterans from two different genera: Leptohyphes Eaton,
1882 (Leptohyphidae) and Lachlania Hagen, 1868 (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, implying limited upstream dispersal of
adults and some of the altitudinal constraint lying at the adult
stage. Short-term survival of transplanted nymphs was lower than
that of controls, suggesting that the distribution was limited at the
juvenile stage, and that at least some of the altitudinal constraint is
related to the abiotic stream environment.
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Keywords
Ephemeroptera, altitudinal limit, dispersal, Ecuadorian andes, abiotic stressors