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Chironomid (Diptera) distribution and diversity in Tibetan streams with different glacial influence

Authors


Ladislav Hamerlík, Institute of Zoology, Slovak Academy of Sciences, Dúbravská cesta 9, SK-84506 Bratislava, Slovakia. E-mail: ladislav.hamerlik@savba.sk

Abstract

Abstract.  1. We collected chironomid larvae and measured basic environmental variables in eight high mountain streams with different degrees of glacial influence in southern Tibet.

2. In total, 32 chironomid taxa were collected. The Orthocladiinae subfamily dominated both in taxon number and in abundance.

3. Both average taxon number and abundance were lower in glacier-fed streams compared with those of non-glacial origin. The total taxon number collected (γ diversity) was similar regardless of glacial influence. However, spot diversity (α diversity) was higher in non-glacial streams, while glacier-fed streams supported higher species turnover (β diversity).

4. Detrended correspondence analysis scattered the study sites along the first ordination axis, representing a combination of distance from glacier and channel stability. Two-way indicator analysis distinguished three groups of sites. Group 1 represented the sites closest to the glacier and were characterised by unstable channel conditions and low temperature with characteristic taxa Diamesa sp. 1, Orthocladius (Eud.) sp. and Rheocricotopus sp. Group 2 was made up of glacier-fed streams situated further from glaciers, with unstable channels and characterised by Orthocladius (Euo.) sp. Group 3 contained non-glacial streams as well as a glacier-fed stream further from the glacier margin. For these sites, stable channels and high conductivity were characteristic and Cricotopus (C.) sp., Pseudosmittia sp, Polypedilum sp., Eukiefferiella gracei group and Pagastia sp. 1 were the dominating taxa.

5. We propose a general distribution pattern of chironomids in the streams of glacial and non-glacial influence in Tibet, which is in accordance with the model proposed by Milner et al. (2001a) Freshwater Biology, 46, 1833–1847.

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