Effects of grazing on taxonomic and functional diversity of benthic macroinvertebrates of six tributary streams of the eastern shore of Lake Hövsgöl, Mongolia

ABSTRACT Overgrazing is one of the major land-use impacts in Mongolia leading to habitat degradation and subsequent impairment of biological diversity. This study examined macroinvertebrate diversity among sites with different grazing intensities in Hövsgöl, Mongolia, to test whether the taxonomic and functional structure of the macroinvertebrate community differs among streams with different grazing intensity. The 14 551 total identified specimens comprised 78 genera in 27 macroinvertebrate families from the 6 study streams. Exponential Shannon index and weighted functional diversity were significantly higher in low grazing sites than in moderate and high grazing sites; no significant difference was found between moderate to high grazing intensity. Macroinvertebrate community composition was not significantly different between low and moderate or low and high grazing intensity sites. SIMPER analysis revealed the taxon with the highest contribution to dissimilarity among the levels of grazing. Thirteen trait categories from 8 traits differed significantly between sites with varying grazing pressure. The community-weighted means for 4 of these traits were filtered by high grazing intensity: dissemination, resistant form, current velocity, and saprobity. Although the other 4 traits differed significantly, they did not respond directly to grazing intensity. Further knowledge of traits, especially regarding physiological capabilities, is needed to better understand macroinvertebrate/environment relationships, but overall, these findings suggest that macroinvertebrate diversity components were affected by grazing.