Abstract

VON ELLENRIEDER, Natalia. Composition and structure of aquatic insect assemblages of Yungas mountain cloud forest streams in NW Argentina. Rev. Soc. Entomol. Argent. [online]. 2007, vol.66, n.3-4, pp.57-76. ISSN 0373-5680.

Thirty three lotic environments in the Yungas mountain cloud forest of NW Argentina were sampled both in undisturbed forest areas and sites altered by human activities. Aquatic insects of 143 taxa in 55 families were collected. Cluster analysis suggested altitude as one of the main structuring variables of aquatic insect communities in these streams, and its importance was confirmed by non-metric multidimensional scaling (NMS); the environmental parameters measured that were best correlated with the ordination were altitude, water temperature, latitude and channel variables (width, percentage of large and small woody debris, of undercut banks, cobble and coarse gravel). Multi response permutation procedures (MRPP) showed streams in well preserved areas to significantly differ in their composition from streams in disturbed areas. Proportion of Elmidae and of Plecoptera individuals and number of Trichoptera taxa were the biological metrics best correlated with the local disturbance gradient, suggesting that an 'ElPT' index could be a useful component in the evaluation of the ecological status of these environments. Indicator species analyses identified some potential indicators of stream condition and disturbance factors affecting these streams.

Keywords : Diversity; Community structure; Indicator species; Biological metrics; Elmidae.

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