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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: Analysing 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 inspirations for biodiversity conservation in the 'World's Third Pole' that is highly sensitive to global change. [ABSTRACT FROM AUTHOR]

The extent to which the sequence and timing of important events on Earth have influenced biological evolution through geological time is a matter of ongoing debate. In this context, the phylogenetic history of aquatic insects remains largely elusive, and our understanding of their chronology is fragmentary and incomplete at best. Here, after gathering a comprehensive data matrix of 3125 targeted rRNA and protein-coding gene sequences from nine independent gene portions, we built a well-supported time-calibrated phylogenetic tree comprising almost 1200 genera that represent a large proportion of extant families of dragonflies and damselflies (Odonata), mayflies (Ephemeroptera), stoneflies (Plecoptera), and caddisflies (Trichoptera). We reviewed the main evolutionary and historical scenarios for each aquatic insect lineage as revealed by our best-scoring molecular tree topology, major ancient radiations, calibrated divergence estimates, and important events in geological history related to the spatial arrangement of land masses, continental drift, and mass extinctions. Molecular dating using the birth-death model of speciation, with a lognormal-relaxed model of sequence evolution informed by transcriptomic constraints, suggested that (i) dragonflies and damselflies first radiated approximately 220 million years (Ma) ago and most extant lineages thrived independently after the Triassic–Jurassic (Tr–J) extinction event; (ii) mayflies underwent bursts of diversification during the Cretaceous; (iii) ancestral divergence separating the stonefly suborders Arctoperlaria and Antarctoperlaria was consistent with geographical isolation after vicariant fragmentation and tectonic splitting of the supercontinent Pangaea around 170 Ma ago; and (iv) the most recent common ancestors of caddisflies extended back to the time of Pangaea, supporting the earliest offshoot of the 'retreat-making' Annulipalpia and a sister relationship between the predatory free-living Rhyacophilidae and Hydrobiosidae. Our 'Tree of Life' of aquatic insects also resolved shallow phylogenetic relationships related to key evolutionary innovations, such as the convergent evolution of exophytic oviposition in dragonflies or the Jurassic origins of the burrowing lifestyle in mayflies. In this study, we also illustrate how our time-calibrated phylogeny can help to integrate phylogenetic aspects in biogeographical and ecological research across the world. To do so, we used three empirical datasets of stream insects from subarctic Finland, northeastern Spain, and southeastern Tibet as exemplary cases. These examples of application tested ecogeographical mechanisms related to (i) the responses of size structural resemblances to phylogenetic constraints, and patterns of (ii) phylogenetic relatedness and (iii) phylogenetic uniqueness along elevational and flow-intermittence gradients, respectively. We emphasise how specific details capturing different aspects of phylogenetic variation are dependent on the geological, geographical, and environmental contexts in different drainage basins. We finally highlight potential venues for future research, including evaluations of geographical patterns of phylogenetic diversity in space and time, evolution of ecological characters in relation to palaeoclimatic variation, and development of complementary algorithms for conservation prioritisation of evolutionarily valuable bioregions for aquatic insects. Overall, we hope that this work will stimulate multidisciplinary research efforts among different areas of the biogeosciences towards safeguarding the phylogenetic heritage of extant aquatic insects across the world. • Mapping the evolutionary pathway of aquatic insects has proven to be a complex task. • We present the largest time-calibrated phylogeny for key groups of aquatic insects. • Important events in Earth's geological history shaped aquatic insect macroevolution. • Phylogenetic variation is dependent on the geographical and environmental context. • This 'Tree of Life' contains a great deal of useful information for biogeosciences. [ABSTRACT FROM AUTHOR]