Cycas mindorensis (Cycadaceae), a new species from Mindoro Island, Philippines, and its biogeographic significance within section Wadeae

A new species, Cycas mindorensis Agoo, Madulid & Linis sp. nov., is described from Mindoro Island, Philippines. It belongs to section Wadeae based on its seeds with ribbed sclerotesta and narrowly triangular, deeply pectinate megasporophyll lamina, characteristics shared with other members of this clade. It is distinguished from related species ( C. aenigma, C. curranii, C. saxatilis, and C. wadei ) by its larger seeds (50–60 mm in length, the largest in the section) bearing 13–21 sharp-edged longitudinal ribs on the sclerotesta and a narrowly triangular, deeply pectinate megasporophyll lamina with 7–9 fine lateral spines per side. A key to species in section Wadeae based on seed characters is provided, with C. mindorensis uniquely diagnosed by its broadly ellipsoid seeds with deeply fluted, sharp-edged longitudinal ribs. The species is restricted to calcareous soils within the Jurassic Mansalay Formation in Bongabong, Oriental Mindoro. This discovery extends the known range of section Wadeae eastward from Palawan to Mindoro. The population is extremely small, highly localised, and threatened by agricultural expansion and slash-and-burn farming. Consequently, the species is assessed as Critically Endangered. The finding highlights the evolutionary importance of microcontinental drift and isolated limestone habitats in shaping Philippine cycad diversity and underscores the urgent need for targeted conservation measures.