The family Euphorbiaceae is one of the most taxonomically complex and diverse family among the angiosperm. Therefore, this study aims to document the pollen morphology of the Euphorbiaceae taxa collected from different geographical regions of the Hainan Island South China, to strengthen the taxonomy and support the subfamilial classification. The Euphorbiaceae includes 23 species and 10 genera of the bi-ovulate subfamily Phyllanthoideae and tri-ovulate Crotonoideae, Euphorbioideae, and Acalyphoideae were examined under light and scanning electron microscopy. The principal component analysis was performed by using six variables to show variation and relationships between the species. A significant variation was found in the pollen morphology (exine and colpus sculpturing). The croton-type pattern of the pollen was found the diagnostic trait of the Crotonoideae. The Euhphorboideae taxa were mostly homogenous however, variation was found in the muri pattern. The Acalyphoideae, have fossulate scabrate and verrucate exine sculpturing that can delimit from the rest of sub-families. The Phyllanthoideae, showed reticulate exine, tri to tetra-colporate having various colpus morphology. The maximum pollen size was found in Croton hirtus (59.49 × 60.86 μm) and minimum in Acalypha indica (10.86 × 73 μm). Similarly, the maximum colpus width was observed in Euphorbia pulcherrima (8.3 μm). Hence pollen traits have relevance in the taxonomy and phylogenetic of the family to define species boundaries at various taxonomic levels. This study can support and strengthen the taxonomy of subfamilies and fill the palynological gap of these taxa in Hainan Island and will contribute to future systematic studies of the Euphorbiaceae.
Some selected taxa of the four subfamilies including Crotonoideae, Euphorbioideae, Acalyphoideae, and Phyllanthoideae (Euphorbiaceae) were collected from different geographical regions of the Hainan Island. The pollen of these taxa was observed under both light and scanning electron microscopy. A significant variation was found in both qualitative features including (exine and colpus surface membrane morphology) and quantitative traits (polar axis, equatorial diameter, colpus length and width, polar area and clava diameter. Based on the pollen traits, our study suggested the eurypalynous condition of the family Euphorbiaceae. Pollen features were found to have a significant taxonomic and phylogenetic potential and can be used as an additional tool to define species boundaries at various taxonomic ranks and support the subfamilial classification of the family Euphorbiaceae.
Keywords: Euphorbiaceae; LM and SEM; pollen micromorphology; taxonomic relevance.
© 2022 Wiley Periodicals LLC.