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Verbesina encelioides (Cav.) Benth. & Hook. f. ex A. Gray, golden crownbeard, is a sunflower-like herbaceous annual plant ranging in height from 0.3 to 1.7 m with showy yellow flowers. It is native to the southwestern United States, the Mexican Plateau, and other parts of tropical America. Its invasive characteristics include high seed production (as many as 300-350 seeds per flower and multiple flowers per plant), seed dormancy, ability to tolerate dry conditions, and possible allelopathic effects. Disturbed areas with a relatively sandy substrate within warm, arid climate zones are vulnerable to invasion by V. encelioides. Veresina encelioides is found on all of the main Hawaiian islands except Ni'ihau but is particularly problematic on Midway and Kure Atoll, where it may threaten the habitat of nesting birds such as Laysan and black-footed albatrosses and Christmas and wedge-tailed shearwaters. Many other Pacific islands with similar habitats could be invaded by the V. encelioides. The plant has become naturalised in many other U.S. states, parts of South America, the Bahamas, Cuba, the Dominican Republic Puerto Rico, parts of Europe, Saudi Arabia, India, Ethiopia, Morocco, Botswana, Namibia, Israel, and Australia. It is a pest of various crops in the southern United States and India and is poisonous to sheep and cattle. Verbesina encelioides can be controlled via herbicides or mechanical means, but measures must be repeated due to the presence of persistent seed banks. Further research on V. encelioides is needed to understand its population dynamics, allelopathic properties, and impacts on natural ecosystems.

Merremia peltata, disturbance ecology, tropical cyclones and Samoa. The biology and ecology of Merremia peltata are not well understood. While some regard the species as an exotic invader of Pacific Island ecosystems (Meyer. 2000). others identify the plant as a native species likely to be harmful to native ecosystems (Whistler, 1995a. 2002) or as either native or ancient Polynesian introduction behaving invasively (Space and Flynn.(2002). In Samoa, this species occurs up to an elevation of around 300 meters (Whistler 1995a). and thus only affects lowland ecosystems. This species increases its distribution and abundance in two ways, either vegetatively. by sprawling into neighboring areas and rooting from its nodes or by seeds, although early research in the Solomons observed a low seed viability rate, and creeping may thus be its primary means of reproduction (Bacon. 1982). M. peltata has apparently been in the Pacific for hundreds of years (Whistler, pers. com.) but has only become invasive in the years following tropical cyclones Ofa (1990) and Val (1991) according to comments from local government officials. Disturbance thus appears to be an ecological contributing factor to this invasion.