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.