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| Derris rubricosta Boonprajan & Sirich., in Boonprajan, Leeratiwong et Sirichamorn, 2024. |
Abstract
Derris rubricosta Boonprajan & Sirich., sp. nov., a new species of the genus Derris Lour. (Fabaceae) was discovered in Peninsular Thailand. The overall morphology demonstrates that the species most resembles D. pubipetala. Nevertheless, the species has several autapomorphies differentiating it from other Derris species, e.g., the presence of reddish midribs of the mature leaflets, sparsely hairy stamen filaments, prominent hairs at the base of the anthers, and presence of glandular trichomes along the leaflet midrib. Additionally, HPLC fingerprints of this species showed a distinction from D. pubipetala by the absence of phytochemical compound peaks after 13 min. Retention Time (RT). Results from molecular phylogenetic analyses also strongly supported the taxonomic status as a new species.
Key words: Anatomy, Derris, HPLC fingerprint, molecular phylogeny, morphology, phytochemical
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| Derris rubricosta, sp. nov. A habit and habitat B leaves C stem D young reddish leaflets E reddish midribs of mature leaflets F, G close-up of midrib on adaxial and abaxial surface respectively H inflorescences and foliage I, J close-up of inflorescence, showing flower buds and brachyblasts K close-up of flower and buds. All photos were taken at Pha Dam Forest Ranger Unit in Songkhla province. Photos by Punvarit Boonprajan (A, B, D–G) and Charan Leeratiwong (C, H–K). |
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| Comparative macro- and micro-morphological characters of leaflets and flowers of Derris rubricosta, sp. nov. (A, A1–A10) and D. pubipetala (B, B1–B10) A, B a branch with leaves and inflorescences |
Derris rubricosta Boonprajan & Sirich., sp. nov.
Diagnosis: The species has several autapomorphies distinguishing it from other Derris species. It is the only species that has reddish midribs on the lower surface of mature leaflets. Its style is sericeous at the base and gradually becomes glabrous apically (vs. thinly hairy at the base and mostly glabrous throughout in other Derris species). Derris rubricosta has prominent hairs below the anthers (vs. glabrous anthers in all other Derris species). It is morphologically similar to D. pubipetala Miq., but differs by its leaflet midrib colour (reddish vs. green), number of leaflets or leaf (9–11 vs. 5–9), colour of its corolla (pale pink to pink vs. white), wing petal margin (straight vs. revolute), stamen filament indumentum (sparsely hairy vs. glabrous), indumentum presence below the anthers (present vs. absent), floral disc shape (indistinct to more-or-less 10-lobed vs. annular).
Etymology: The specific epithet refers to the striking reddish colour of the midrib of the mature leaflets which has never been found in other species of Derris.
Vernacular names: “Khruea lai leeratiwong” (เครือไหลลีรติวงศ์) means “Leeratiwong’s Derris”, in Thai, in honor of Associate Professor Dr. Charan Leeratiwong, who discovered and collected the type specimens.
Distribution: Peninsular Thailand: Songkhla (Rattaphum district, Sadao district) (Fig. 4). Estimated population of more than 2,500 mature individuals were found during field survey between 2019 and 2022 in its type locality and nearby areas.
Punvarit Boonprajan, Charan Leeratiwong, Yotsawate Sirichamorn. 2024. From Morphology to Molecules: A Comprehensive Study of A novel Derris Species (Fabaceae) with a rare flowering habit and reddish leaflet midribs, discovered in Peninsular Thailand. PhytoKeys. 237: 51-77. DOI: 10.3897/phytokeys.237.112860
