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Conservation of rare species faces challenges arising from uncertainties in species recognition, interspecific gene flow and global climate change.Betula microphyllaandBetula halophilaare endangered species in Xinjiang province, Northwest China, where they occur with the abundantBetula pendula. The species status ofB. halophilaremains dubious. The extent of gene flow between B.microphyllaandB. pendularemain unexplored. Here, we first resolve the identity ofB. halophilaand then assess the extent of gene flow betweenB. microphyllaandB. pendulausing restriction-site associated DNA sequencing (RADseq). We sequenced 40B. pendulaindividuals, 40B. microphyllaindividuals, oneB. halophilaindividual and sevenB. tianshanicaindividuals. Our molecular analyses show thatB. halophilaandB. microphyllarefer to the same species. STRUCTURE analyses show unidirectional genetic admixture fromB. pendulatoB. microphylla. The ABBA-BABA test indicates that the genetic admixture reflects introgression rather than incomplete lineage sorting. Furthermore, we identified 233 functional genes within the introgressed regions with eight genes related to salt-tolerance, suggesting the possibility of potential adaptive introgression. Our study shows an urgent need to conserve the genetically pure populations ofB. microphyllaand to shift conservation efforts fromB. halophilatoB. microphylla. In addition, ex-situ conservation of B. microphylla and conservation strategies to avoid genetic swamping byB. pendulaandB. tianshanicashould be implemented.

Societal Impact Statement In rapidly changing environments species conservation can be hindered by uncertainties in distinguishing closely related species. Cryptic ongoing hybridization can add further uncertainty and could be beneficial or destructive. Here, we show that a declining birch tree species is hybridizing with a more widespread relative in the Junggar basin, NW China, and their hybrids have been previously named as rare sub‐species. Given the declining numbers of this birch tree, we suggest that conservation effort should aim to slow the rate of anthropogenic habitat loss at this hybrid zone and preserve its pure populations away from the hybrid zone. Summary In areas where closely related species meet, the possibility that they may hybridize must be taken into account by conservationists. Hybridization may have positive or negative consequences for the long‐term future of species. If present, its dynamics need to be understood. Betula microphylla is a declining wetland tree species in NW China that forms a continuum of leaf morphology and geographic distribution with its relative Betula tianshanica. We use ecological niche models to predict the distribution of B. microphylla and B. tianshanica. We use restriction site‐associated DNA sequencing and SSRs to resolve their genetic structure and patterns of allele sharing. Ecological niche models predict an expansion of the range of B. tianshanica into that of B. microphylla since the Last Glacial Maximum and the contraction of B. microphylla's range in the future. Genetic data suggest that the two species have hybridized in the Junggar basin and in the Tianshan Mountains where the two species have co‐occurred in the recent past and in the Altay Mountains where there are no records of B. tianshanica occurrence. Rare populations previously identified as sub‐species of B. microphylla were shown to be of hybrid origin. Further research is needed on the costs and benefits of hybridization between B. microphylla and B. tianshanica in the changing environment of NW China. Our current data suggest that conservation effort should aim to slow the rate of anthropogenic habitat loss at the hybrid zone in the Junggar basin and preserve pure populations far away from the hybrid zone in the Altay Mountains.

SummaryMolecular markers can allow us to differentiate species that occupy a morphological continuum, and detect patterns of allele sharing that can help us understand the dynamics of geographic zones where they meet. Betula microphylla is a declining wetland species in NW China that forms a continuum of leaf morphology with its relative Betula tianshanica.We use ecological niche models (ENM) to predict the distribution of B. microphylla, B. tianshanica and the more commonly occurring B. platyphylla. We use restriction-site associated DNA sequencing and SSRs to resolve their genetic structure and patterns of allele sharing.ENM predicted an expansion of suitable range of B. tianshanica into B. microphylla since the Last Glacial Maximum and the contraction of B. microphylla’s range in the future. We resolved the species identification of some intermediate morphotypes. We found signatures of bidirectional introgression between B. microphylla and B. tianshanica with SNPs showing more admixture than SSRs. Introgression from B. microphylla into B. tianshanica was greater in the Tianshan Mountains where the two species have occurred in proximity. Unexpectedly, introgression from B. tianshanica into B. microphylla was widespread in the Altay Mountains where there are no records of B. tianshanica occurrence.This presence of B. tianshanica-derived alleles far beyond the species’ current range could be due to unexpectedly high pollen flow, undiscovered populations of B. tianshanica in the region, incomplete lineage sorting, or selection for adaptive introgression in B. microphylla. These different interpretations have contrasting implications for the conservation of B. microphylla.

Betula microphylla (Betulaceae) is a species widely distributed in Xinjiang China and in Mongolia and Siberia of Russia. In this study, we described the complete chloroplast genome of B. microphyll...

Boron, an essential plant micronutrient, was effective in the form of potassium tetraborate for control of postharvest gray mold caused by Botrytis cinerea on table grapes stored at room temperature or at 0 degrees C. The inhibition of fruit decay was closely correlated with boron concentrations and partially influenced by pH value of the solution. Boron strongly inhibited spore germination, germ tube elongation, and mycelial spread of B. cinerea in the culture medium. Application of boron at 1% caused the appearance of abnormal spores (disrupted) in some cases. By using propidium iodide fluorescent staining, loss of membrane integrity in B. cinerea was observed after boron treatment. Furthermore, boron led to the leakage of cellular constituents (soluble proteins and carbohydrates) from hyphae of B. cinerea. These data suggest that the mechanisms by which boron decreased gray mold decay of table grapes may be directly related to the disruption effect of boron on cell membrane of the fungal pathogen that resulted in the breakdown of the cell membrane and loss of cytoplasmic materials from the hyphae.