Colocasia sookchaloemiae (Araceae), a new species from northeastern Thailand.

Colocasia sookchaloemiae (Araceae) is described from Phu Pha Yol National Park (northeastern Thailand). It is morphologically similar to C. fallax, from which it differs in having seasonal dormancy (vs. evergreen), broader and non-glaucous laminae (vs. narrower and slightly glaucous beneath), a speckled green ovary (vs. mostly green), a convex stigma with a depressed center (vs. 3-lobed), a sparsely hairy sterile interstice (vs. glabrous), and a thicker stipitate appendix (vs. slender, often sessile, or shortly stipitate). A comparative study of living plants, cultivated specimens, and herbarium material (including types) supports its recognition as a distinct species. The new taxon grows on rocky cliffs in dry dipterocarp and mixed deciduous forests at 350-400 m a.s.l., and it is currently known from Mukdahan and Sakon Nakhon provinces. A preliminary IUCN assessment indicates that the species is Data Deficient (DD).