Abstract
Material from the Cyperus appendiculatus group was collected from Ascension Island and compared using a common garden study and to herbarium specimens from throughout the geographical range. Cyperus stroudii is described as a new species, known only from Ascension Island in the South Atlantic Ocean, it closest relative is C. appendiculatus also native to Ascension Island and Brazil. Cyperus stroudii differs from C. appendiculatus in its dwarf habit and other morphological characteristics, and these characteristics are retained under common environmental conditions indicative of genomic differences.