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First Page

89

Last Page

101

Abstract

Oceanic archipelagos often hold very specialized floras with high degrees of endemism. These floras are frequently highly vulnerable to disturbance by natural causes and human intervention. The Juan Fernandez Islands (Chile) in the Pacific Ocean are a small archipelago of only three islands. Since discovery in 1574 by Juan Fernandez, human activities have altered floristic composition and survival circumstances of the endemic species. In this paper we document past and present means of disturbance, both anthropogenic and natural, which have influenced the native vegetation. The most destructive past activities have been logging and .introduction of animals and plants, both deliberately and inadvertently. At the present time, exotic organisms are still introduced as pets, ornaments, or for soil conservation. All pose serious threats to the natural vegetation as shown by altered floristic composition, populational decline of endemic taxa, and even extinction. Weeds that form impenetrable thickets are Aristotelia chilensis, Rubus ulmifolius, and Ugni molinae. Recent introductions include the aggressive Lantana camara and Lonicera japonica. Examples of endemic taxa in need of conservation are Dendroseris, Lactoris, and Robinsonia. Previous studies reveal that island taxa frequently have low levels of genetic variation, a pattern also seen in many endemic taxa of the Juan Fernandez Islands. Conservation programs are urgently needed that emphasize physical and biological measures for controlling alien weeds and animals.

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© 1998 Tod F. Stussy, Ulf Swenson, Daniel J. Crawford, Gregory Anderson, Mario Silva O.

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