| 摘要: |
| 马兜铃科属级范畴界定争议是长期困扰该科分类学研究的核心问题，宏观形态性状易受趋同演化干扰，亟需补充稳定的微观特征。为明确花粉形态的分类学价值，该研究分别选取马兜铃科关木通属11种1亚种与马兜铃属7 种植物为对象，采用改良 DMP 脱水制样、扫描电镜高精度观测结合多元统计分析的技术流程，对花粉大小、形态轮廓及外壁纹饰等关键性状进行系统量化，并通过主成分分析（PCA）与聚类分析（UPGMA）揭示其分类学意义。结果表明：（1）研究类群花粉均为单粒近球形（P/E=1.02~1.13），表现出明显的科级形态保守特征。（2）两属花粉形态分化显著，关木通属多为中小型花粉，极轴长 23.21～28.17 μm，外壁以微细网状纹饰为主；马兜铃属以中大型花粉为主，极轴长 25.44～46.14 μm，多具粗网状或脑纹状纹饰，花粉体量与外壁纹饰类型可作为两属划分的重要鉴别依据。（3）网眼直径 0.17～0.40 μm、网脊宽度 0.48～2.89 μm 及极赤比等量化参数，可有效区分近缘物种，其中苞叶马兜铃特化的萌发沟结构、巨花马兜铃独特的脑纹状纹饰，均为物种独特鉴别性状。（4）主成分与聚类分析结果一致，支持关木通属与马兜铃属独立分化，构建的花粉大小-形状-纹饰三级量化判别体系，可实现疑难近缘种的精准界定。本研究完善并补充了马兜铃科植物的孢粉基础数据，优化适配了薄壁柔嫩花粉的电镜制样方法，可为该科分类系统修订、物种划分及药用野生资源保育提供可靠的孢粉学依据，同时也为被子植物孢粉研究由传统定性描述转向量化鉴别提供了数据。 |
| 关键词: 马兜铃科，花粉形态，分类鉴定，DMP制样，系统演化 |
| DOI：10.11931/guihaia.gxzw202605018 |
| 分类号: |
| 基金项目:中国科学院仪器设备功能开发创新项目（Y8GK051B01）；云南省科技厅重点研发计划建设面向南亚东南亚科技创新中心专项（202403AK140016）。 |
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| Pollen morphology of 19 species of Aristolochiaceae and its taxonomic significance |
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ZHANG Rui1*, YANG Bin2, TANG Ting1, ZHANG Shuhong3, LIU Wenjun3, ZHANG Rui1
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1. Institutional Center for Shared Technologies and Facilities, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, Yunnan, China; 2. Southeast Asia Biodiversity Research Institute, Chinese Academy of Sciences & Center for Integrative Conservation, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, Yunnan, China; 3. Center for Gardening and Horticulture, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, Yunnan, China
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| Abstract: |
| Persistent disputes regarding generic circumscriptions within Aristolochiaceae have long hindered taxonomic research of this family, as macroscopic morphological traits are prone to convergent evolution. This highlights an urgent need for stable micromorphological diagnostic evidence. To clarify the taxonomic significance of pollen morphology, we sampled 11 species and one subspecies of Isotrema, alongside seven species of Aristolochia for this study. We employed a modified DMP dehydration preparation protocol coupled with high-resolution scanning electron microscopy (SEM) and multivariate statistical analysis to quantitatively characterize key pollen traits, including pollen size, outline shape and exine ornamentation. We further performed principal component analysis (PCA) and unweighted pair-group method with arithmetic averaging (UPGMA) clustering to reveal the taxonomic implications of pollen micromorphology. The results were as follows: (1) All pollen grains from the investigated taxa are monads and subspherical, with polar/equatorial axis ratios (P/E) of 1.02-1.13, exhibiting pronounced family-level morphological conservatism. (2) Pollen morphology differed distinctly between the two genera. Isotrema generally produces small to medium-sized pollen grains with polar axis of 23.21-28.17 μm, whose exine is predominantly finely reticulate. In contrast, Aristolochia bears medium to large pollen grains with polar axis length of 25.44-46.14 μm, characterized by coarsely reticulate or cerebroid exine ornamentation. Pollen size and exine ornamentation type constitute critical diagnostic traits for distinguishing these two genera. (3) Quantitative metrics such as lumina diameter (0.17-0.40 μm), muri width (0.48-2.89 μm) and P/E ratio enable reliable discrimination of closely related congeneric species. The distinctive germinal aperture structure of Aristolochia bracteolata and the unique cerebroid exine ornamentation of A. gigantea serve as exclusive species-specific diagnostic traits. (4) PCA and cluster analyses yielded congruent results, supporting the independent evolutionary divergence of Isotrema and Aristolochia. The established three-tier quantitative discrimination framework based on pollen size, shape and exine ornamentation enables precise delimitation of taxonomically ambiguous closely related taxa. This study enriches the fundamental palynological dataset for Aristolochiaceae, and optimizes SEM preparation protocols tailored to thin-walled, fragile pollen grains. It provids reliable palynological evidence for taxonomic revision, species boundary delimitation and conservation management of wild medicinal Aristolochiaceae resources. Moreover, this research provides baseline data to advance angiosperm palynology from traditional qualitative morphological documentation toward quantitative taxonomic identification. |
| Key words: Aristolochiaceae, pollen morphology, taxonomic delimitation, DMP dehydration preparation, phylogenetic evolution |
