Bidens amplectens, the Waiʻanae kokoʻolau, is a species of flowering plant in the family Asteraceae. It belongs to the genus Bidens, collectively called kokoʻolau or koʻokoʻolau in the Hawaiian language. It is found in coastal and dry lowland habitats in the Waiʻanae Range on Oʻahu. It is threatened by habitat loss due to the spread of invasive weeds and brush fires. The species is also threatened by climate change and habitat degradation, and herbivory. Bidens amplectens is currently listed as endangered under the Endangered Species Act. General description Bidens amplectens is a member of the sunflower family (Asteraceae). It is an herb with branched stems, from 1.5 to 3 m (5 to 10 ft) tall. It has sparsely pubescent leaves that are pinnately compound, 9 to 15 cm (14 to 22 in) long with 3 to 5 leaflets. Cymes with lateral branches have 10 to 30 flower heads. Ray florets are yellow, 7 to 9 per head, and disk florets are 40 to 60 per head with yellow corollas. Achenes (dry fruit) are gray, straight, wingless, 5 to 8 mm (0.2 to 0.3 in) long and 1 mm (0.04 in) wide, sparsely setose (bristly) on margins and faces. Life history Bidens amplectens is a short-lived annual or perennial dicot herb. This species' lifespan is between 1 to 10 years. Little is known about the life history of Bidens amplectens. Flowering was observed in April, May, October, and November. Bidens amplectens''' pollination vectors, seed dispersal agents, specific environmental requirements, and limiting factors are unknown. Bidens amplectens is known to hybridize with Bidens torta, another flower native to O'ahu. Ecology Diet Bidens amplectens is a photosynthetic autotroph. Pollinators Features of the Bidens genus’ flowers indicate pollination by birds, however, this has not been observed in nature. Habitat The habitat for Bidens amplectens includes cliffs and talus slopes in lowland dry shrubland on the windward side of the Waiʻanae mountains. This species was noted as present in 2012 in coastal and lowland dry habitats. The coastal ecosystem on O'ahu includes mixed herblands, shrublands, and grasslands, from sea level to 980 ft (300 m) in elevation. It is generally within a zone above the influence of waves to within 330 ft (100 m) inland. The coastal vegetation zone is typically dry, with annual rainfall of less than 20 in (50 cm). Windward rainfall may be higher. Biological diversity is low to moderate in this