Diverse forms of nanoscale architecture generate structural colour and perform signalling functions within and between species. Structural colour is the result of the interference of light from approximately regular periodic structures; some structural disorder is, however, inevitable in biological organisms. Is this disorder functional and subject to evolutionary selection, or is it simply an unavoidable outcome of biological developmental processes? Here we show that disordered nanostructures enable flowers to produce visual signals that are salient to bees. These disordered nanostructures (identified in most major lineages of angiosperms) have distinct anatomies but convergent optical properties; they all produce angle-dependent scattered light, predominantly at short wavelengths (ultraviolet and blue). We manufactured artificial flowers with nanoscale structures that possessed tailored levels of disorder in order to investigate how foraging bumblebees respond to this optical effect. We conclude that floral nanostructures have evolved, on multiple independent occasions, an effective degree of relative spatial disorder that generates a photonic signature that is highly salient to insect pollinators.

Historical geoclimatic events have shaped the distribution patterns and intraspecific divergence of plants. Numerous phylogeographical studies in China have focused on the Qinghai-Tibetan Plateau and surrounding areas due to the complex topography and high species diversity, but the impact of Neogene events and Quaternary climatic change on the flora of subtropical China remains poorly understood. Quercus glauca, a widespread tree of East Asian subtropical evergreen forests, has rich fossil records dating back to the Neogene, and it provides a good model to explore the impact of paleogeoclimate changes on East Asian subtropical forests. We used three chloroplast DNA (cpDNA) intergenic spacer regions and ecological niche modeling (ENM) to analyze the divergence pattern and demographic history of Q. glauca in China and Japan. A total of 33 haplotypes were detected. The phylogenetic analysis revealed two major haplotype lineages (Southwest China vs. Southeast China and East China Sea). The limited dispersal ability of seeds and complex topography resulted in the high total, inter-and intrapopulation haplotype diversity. The fossil-constrained BEAST analysis revealed a lineage diversification in the late Miocene-Pliocene. The formation of complex topography changes since Miocene in east Himalaya and adjacent area might be the key factor that triggered the intraspecific divergence of Q. glauca. Haplotype spatial distribution, ENM, mismatch distribution, and neutrality tests suggest that Q. glauca in Southeast China experiences expansion, and the current distribution in region III might be shaped by southward expansion from regions I and II after last glacial maximum (LGM). Regions I and II were the potential glacial refugia of Q. glauca.

Effectively conserving biodiversity with limited resources requires scientifically informed and efficient strategies. Guidance is particularly needed on how many living plants are necessary to conserve a threshold level of genetic diversity in ex situ collections. We investigated this question for 11 taxa across five genera. In this first study analysing and optimizing ex situ genetic diversity across multiple genera, we found that the percentage of extant genetic diversity currently conserved varies among taxa from 40% to 95%. Most taxa are well below genetic conservation targets. Resampling datasets showed that ideal collection sizes vary widely even within a genus: one taxon typically required at least 50% more individuals than another (though Quercus was an exception). Still, across taxa, the minimum collection size to achieve genetic conservation goals is within one order of magnitude. Current collections are also suboptimal: they could remain the same size yet capture twice the genetic diversity with an improved sampling design. We term this deficiency the ‘genetic conservation gap’. Lastly, we show that minimum collection sizes are influenced by collection priorities regarding the genetic diversity target. In summary, current collections are insufficient (not reaching targets) and suboptimal (not efficiently designed), and we show how improvements can be made.

This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

With % of trees (. , species) threatened with extinction there is an urgent need for botanical gardens to protect threatened trees in dedicated conservation collections. Species conservation is mentioned in the mission statements of most major botanical gardens, yet the actual conservation value of existing ex situ tree collections is low. We conducted interviews with members of the botanical garden community and organized a symposium at the th Global Botanic Gardens Congress to identify challenges and collect recommendations to improve living ex situ tree collections. We summarize and evaluate this information to facilitate gardens becoming more effective agents for global tree conservation. Experts agree that gardens offer valuable strengths and assets for tree conservation. Some challenges exist, however, including a lack of strategic conservation focus, collection management limitations, gaps in fundamental biological information for trees, and a lack of global coordination. Solutions are offered to facilitate gardens and arboreta of all sizes to participate more effectively in tree conservation. Prioritizing genetically diverse tree collections, participating in conservation networks, developing tree-specific conservation models and guidelines, and strengthening tree science research efforts are a few examples. Most importantly, a more coordinated global effort is needed to fill knowledge gaps, share information, and build conservation capacity in biodiversity hotspots to prevent the loss of tree species.

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