Transfer of six species of Spiradiclis Blume to Ophiorrhiza L. (Rubiaceae)

Abstract

The genus Ophiorrhiza Linnaeus (1751: 150) (Ophiorrhizeae, Rubioideae, Rubiaceae) comprises of ca. 318 taxa in tropical and tropical subtropical Asia, extending to Australia, New Guinea and the Pacific Islands (Darwin 1976, Chen & Taylor 2011, Bremer & Manen 2000), with its greatest diversity in southeastern Asia (Davis et al. 2009, Hareesh 2017, Hareesh & Sabu 2018). The genus has been revised taxonomically in some geographic regions such as Australia (Halford 1991), China (Lo 1990, Chen & Taylor 2011), India (Deb & Mondal 1997, Hooker 1880, Hareesh & Sabu 2018) and the Pacific (Darwin 1976). In the Flora of China, 73 species were reported, in which 47 species are endemic (Chen & Taylor 2011, Yang et al. 2018, Tu et al. 2018, Wu et al. 2017, 2018, Duan et al. 2019) and mainly occurring in southwestern region of China, commonly growing on humid slopes or along valleys under dense forest (Lo 1999, Yang et al. 2018). Generally, Ophiorrhiza species are annual to perennial suffrutescent herbs or small shrubs with cymose inflorescences. Fruit capsules are broadly obcordate, laterally flattened, papery, dry and usually dehiscent loculicidal (Lo 1990, Deb & Mondal 1997, Chen & Taylor 2011, Hareesh 2017, Wu et al. 2018). The Ophiorrhiza species (O. mungos L. (1753: 150), O. mungos L. var. angustifolia (Thwaites) Hook.f. (1880: 77), and O. rugosa Wall. (1824: 547) var. decumbens (Gardner ex Thwaites) Deb & Mondal (1983: 228)) are commercially important as source of Camptothecin (CPT), a potent anticancer drug as well as antiviral and antimicrobial properties (Rajan et al. 2016, Taher et al. 2020).