Seed coat diversity in some tribes of Cucurbitaceae: implications for taxonomy and species identification

To evaluate their diagnostic value in systematic studies, seed coat morphology for 16 taxa from 11 genera of Cucurbitaceae were examined using stereomicroscopy and scanning electron microscopy. The taxa included representatives of the tribes Benincaseae, Bryonieae, Coniandreae, and Luffeae in order to evaluate their diagnostic value in systematic studies. Macro- and micromorphological characters of their seeds are presented, including shape, color, size, surface, epidermal cell shape, anticlinal boundaries, and periclinal cell wall. The taxonomic and phylogenetic implications of seed coat micromorphology were compared with those of the available gross morphological and molecular data. Seed character analysis offered useful data for evaluating the taxonomy of Cucurbitaceae on both intrageneric and tribal levels. Monophyly of the tribes Bryonieae, Coniandreae, and Luffeae was supported. Moreover, these analyses supported previous biochemical and phylogenetic data, indicating that distinct lineages are present within the tribe Benincaseae, that this tribe is not monophyletic, and that the subtribe Benincasinae is highly polyphyletic. A key is provided for identifying the investigated taxa based on seed characters.为在系统学研究中评估其分类鉴定价值，本研究借助体视显微镜（stereomicroscopy）与扫描电子显微镜（scanning electron microscopy），对葫芦科（Cucurbitaceae）11属的16个类群（taxa）的种皮形态进行了观察分析。所选类群涵盖冬瓜族（Benincaseae）、苦瓜族（Bryonieae）、喷瓜族（Coniandreae）及丝瓜族（Luffeae）的代表类群。本研究报道了供试种子的宏观与微观形态特征，包括形状、颜色、大小、表面纹饰、表皮细胞形态、垂周壁边界以及平周细胞壁。随后，将种皮微观形态所蕴含的分类学与系统发育学意义，与已有的宏观形态及分子数据进行了对比分析。种子特征分析可为葫芦科在属内及族级水平的分类学评估提供有效支撑。苦瓜族（Bryonieae）、喷瓜族（Coniandreae）及丝瓜族（Luffeae）的单系性得到了本研究结果的支持。此外，本次分析佐证了此前的生化及系统发育学数据，表明冬瓜族（Benincaseae）内存在多个独立演化支，该族并非单系类群，且冬瓜亚族（Benincasinae）属于高度多系的类群。本研究还提供了基于种子特征对供试类群进行鉴定的分类检索表。