Diversity and composition of macroinvertebrate assemblages in high-altitude Tibetan streams

Abstract

Knowledge on the ecology of streams at extreme altitudes is relatively sparse. We conducted a preliminary survey of the macroinvertebrate fauna of Tibetan streams in June 2009 and August 2011 and compared streams with different water sources. We collected quantitative samples of macroinvertebrates and measured physicochemical variables at 16 sites (8 each sampling year) at altitudes ranging from 4315 to 5065 m a.s.l. and grouped the sites into 3 types according to origin: glacier-fed, rain-fed, and lake-outlets. We identified 38 taxa, with a mean of 8.9 taxa per site. Overall the benthic fauna was dominated by insects (71%), mainly Diptera (especially Chironomidae). Ephemeroptera, Plecoptera, and Trichoptera were found at nearly all sites but mostly in low numbers; however, the fauna was significantly different in the 2 sampling years, especially due to the proportions of Chironomidae (68% in June 2009 and 10% in August 2011) and Baetidae (6% vs. 35%, respectively). The 3 stream types had significantly different faunas. Rain-fed streams had the highest total taxon richness (γ-diversity), but glacier-fed streams had a slightly higher taxon turnover rate (β-diversity). Percent glacial cover in the catchment and water turbidity explained most of the variability in taxon richness. Although not particularly taxon rich compared to other high-altitude streams, the Tibetan stream fauna showed considerable spatial variability. The fast retreat of the glaciers and permanent snow fields in Tibet makes further studies on distribution patterns and driving forces for aquatic biodiversity urgent.

Distribution and diversity of aquatic macroinvertebrate assemblages in a semi-arid region earmarked for shale gas exploration (Eastern Cape Karoo, South Africa)

“…These taxa were widespread, but not necessarily locally abundant. This is in contrast to the commonly observed pattern of distribution for many organisms, where spatial distribution is positively correlated with average abundance [ 68 – 70 ].…”

Disentangling the effects of dispersal mode on the assembly of macroinvertebrate assemblages in a heterogeneous highland region

“…This lack of association is probably a result of the exceptionally harsh hydrological features in glacier-fed streams as well as the highelevation environmental conditions filtering a large number of the species that reach these sites. Glacial cover in catchments has a negative effect on both species richness and abundance of macroinvertebrates (Maiolini and Lencioni 2001, Laursen et al 2015). These harsh conditions are caused by the cold water and unstable channel conditions Milner 2001, Maiolini andLencioni 2001), ultraoligotrophic conditions Milner 2001, Laursen et al 2015), and high loads of suspended fine inorganic sediment (Holte and Gulliksen 1998).…”

“…These unique conditions make this region ideal for exploring the patterns and processes of community assembly at withinand across-region scales. Macroinvertebrate research in Tibetan freshwater ecosystems has mainly focused on describing the characteristics of species composition and diversity patterns (Laursen et al 2015) and assessing assemblageenvironment relationships (Jiang et al 2013). No previous studies have examined the relative importance of both environmental and spatial effects in structuring metacommunities of stream macroinvertebrates, although similar investigations have been done in some regions of the Himalayas (Tonkin et al 2016b).…”

Multiple facets of stream macroinvertebrate alpha diversity are driven by different ecological factors across an extensive altitudinal gradient

“…To date, the investigations involving ecological drivers for multiple facets of alpha diversity of freshwater communities have mainly been carried out in lowland streams, lakes, or ponds (Heino & Tolonen, ; Saito, Siqueira, et al, ; Tolonen, Vilmi, Karjalainen, Hellsten, & Heino, ). Such studies in highland or alpine streams are still largely lacking and mostly centered on examining taxonomic diversity (e.g., Jacobsen, ; Jiang, Xie, & Chen, ; Kock Laursen, Hamerlik, Moltesen, Seestern Christoffersen, & Jacobsen, ). Alpine regions and streams have attracted increasing interest in recent years owing to the more pristine conditions than in lowland areas, and the high vulnerability to various environmental threats, such as a series of challenges posed by global warming (Tong & Wu, ).…”