DOI: 10.5061/dryad.kwh70rz82
title: Unravelling the factors affecting taxonomic, phylogenetic and functional beta diversity of stream macroinvertebrate communities in the World's Third Pole

description: Aim: Disentangling how stochastic and deterministic processes contribute
 to variation in beta diversity is a common goal for ecologists and
 biogeographers. However, such studies are scarce in alpine streams,
 especially when different diversity facets are considered. Here, we
 combined different approaches to examine the drivers of taxonomic,
 phylogenetic and functional beta diversities and discussed how our results
 can inform community assembly and biodiversity conservation in Tibetan
 streams. Location: Tibet Plateau Taxon: Macroinvertebrates Methods: We
 first partitioned multiple facets of beta diversity (Btotal) into species
 replacement (Brepl) and richness difference (Brich) as well as local
 (LCBD) or species (SCBD) contributions. Then, we applied ordination
 methods to examine the relative importance of local, climatic and spatial
 factors on Btotal, Brepl and Brich, respectively. We explored community
 assembly rules using null models based on trait and phylogeny structure.
 Results: Btotal displayed high values and was primarily driven by
 Brepl. Local, climatic and spatial factors were poor predictors of the
 different facets of beta diversity. Null models showed that the diversity
 metrics did not differ from those of null expectations, suggesting that
 most individual streams might be occupied by species that were merely
 random draws from the functional or phylogenetic pools available in this
 region. Partitioning beta diversity into LCBD and SCBD implied that the
 upper canyon streams were more unique than those at lower elevations and
 can be valuable for biodiversity conservation. Main conclusions: Analyzing
 multiple facets of beta diversity provide important insights into
 community assembly that cannot be acquired by focusing on taxonomic
 diversity only. Using a multi-faceted approach involving species,
 phylogenetic and trait data, our study not only sheds light on the
 assembly mechanisms of macroinvertebrate communities in alpine streams but
 also bring inspiration for biodiversity conservation in the ‘World's
 Third Pole’ that is highly sensitive to global change.
description: In October 2015,
 macroinvertebrate samples were taken from 55 stream sites from the Yarlung
 Zangbo River Basin, of which 28 sites were located in the upper canyon and
 the other 27 were from the lower canyon (Fig. 1). Most of the studied
 streams were pristine or near pristine, with scarcely any human
 interference. At each site, three quantitative samples were taken from
 riffles with a Surber sampler (area: 0.09 m<sup>2</sup>; sieve
 mesh: 500 μm) and were kept in a portable fridge for subsequent
 processing. Benthic animals were handpicked from the sediments on a white
 dissecting tray and were later preserved in 70% ethanol. Based on the
 relevant reference books (Brinkhurst, 1986; Morse et al., 1994; Armitage
 et al., 2012),
 macroinvertebrates were identified to the lowest taxonomic level (i.e.,
 genus or species) wherever possible in the laboratory.