The factors determining gradients of biodiversity are a fundamental yet unresolved topic in ecology. While diversity gradients have been analysed for numerous single taxa, progress towards general explanatory models has been hampered by limitations in the phylogenetic coverage of past studies. By parallel sampling of 25 major plant and animal taxa along a 3.7 km elevational gradient on Mt. Kilimanjaro, we quantify cross-taxon consensus in diversity gradients and evaluate predictors of diversity from single taxa to a multi-taxa community level. While single taxa show complex distribution patterns and respond to different environmental factors, scaling up diversity to the community level leads to an unambiguous support for temperature as the main predictor of species richness in both plants and animals. Our findings illuminate the influence of taxonomic coverage for models of diversity gradients and point to the importance of temperature for diversification and species coexistence in plant and animal communities.

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Recently reported insect declines have raised both political and social concern. Although the declines have been attributed to land use and climate change, supporting evidence suffers from low taxonomic resolution, short time series, a focus on local scales, and the collinearity of the identified drivers. In this study, we conducted a systematic assessment of insect populations in southern Germany, which showed that differences in insect biomass and richness are highly context dependent. We found the largest difference in biomass between semi-natural and urban environments (−42%), whereas differences in total richness (−29%) and the richness of threatened species (−56%) were largest from semi-natural to agricultural environments. These results point to urbanization and agriculture as major drivers of decline. We also found that richness and biomass increase monotonously with increasing temperature, independent of habitat. The contrasting patterns of insect biomass and richness question the use of these indicators as mutual surrogates. Our study provides support for the implementation of more comprehensive measures aimed at habitat restoration in order to halt insect declines.

Cotton (Gossypium hirsutum) fibers are the highly elongated and thickened single-cell trichomes on the seed epidermis. However, little is known about the molecular base of fiber cell wall thickening in detail. In this study, a cotton NAC transcription factor (GhFSN1) that is specifically expressed in secondary cell wall (SCW) thickening fibers was functionally characterized. The GhFSN1 transgenic cotton plants were generated to study how FSN1 regulates fiber SCW formation. Up-regulation of GhFSN1 expression in cotton resulted in an increase in SCW thickness of fibers but a decrease in fiber length. Transcriptomic analysis revealed that GhFSN1 activates or represses numerous downstream genes. GhFSN1 has the ability to form homodimers, binds to its promoter to activate itself, and might be degraded by the ubiquitin-mediated proteasome pathway. The direct targets of GhFSN1 include the fiber SCW-related GhDUF231L1, GhKNL1, GhMYBL1, GhGUT1 and GhIRX12 genes. GhFSN1 binds directly to a consensus sequence (GhNBS), (C/T)(C/G/T)TN(A/T)(G/T)(A/C/G)(A/G)(A/T/G)(A/T/G)AAG, which exists in the promoters of these SCW-related genes. Our data demonstrate that GhFSN1 acts as a positive regulator in controlling SCW formation of cotton fibers by activating its downstream SCW-related genes. Thus, these findings give us novel insights into comprehensive understanding of GhFSN1 function in fiber development.

Summary Aquaporins are thought to be associated with water transport and play important roles in cotton (Gossypium hirsutum) fibre elongation. Among aquaporins, plasma membrane intrinsic proteins (PIPs) constitute a plasma‐membrane‐specific subfamily and are further subdivided into PIP1 and PIP2 groups. In this study, four fibre‐preferential GhPIP2 genes were functionally characterized. The selective interactions among GhPIP2s and their interaction proteins were studied in detail to elucidate the molecular mechanism of cotton fibre development. GhPIP2;3 interacted with GhPIP2;4 and GhPIP2;6, but GhPIP2;6 did not interact with GhPIP2;4. Coexpression of GhPIP2;3/2;4 or GhPIP2;3/2;6 resulted in a positive cooperative effect which increased the permeability coefficient of oocytes, while GhPIP2;4/2;6 did not. GhBCP2 (a blue copper‐binding protein) inhibited GhPIP2;6 water channel activity through their interaction. Overexpression of GhPIP2 genes in yeast induced longitudinal growth of the host cells. By contrast, knockdown of expression of GhPIP2 genes in cotton by RNA interference markedly hindered fibre elongation. In conclusion, GhPIP2 proteins are the primary aquaporin isoforms in fibres. They selectively form hetero‐oligomers in order to regulate their activities to meet the requirements for rapid fibre elongation.