XVI International Botanical Congess

Conservation of plants of oceanic archipelagos depends upon accurate evaluations of existing diversity. Important are historical factors that have shaped existing diversity. History has been important in development of biota of oceanic islands due to short geological life-spans, erosion, and human impact. Six types of historical factors are important. Geological history involves knowledge of volcanic origins followed by subsidence and erosion due to wind and water. This affects biogeographic history, especially immigration, because islands change size and shape. Ecological history deals with competition, speciation and extinction. History of speciation results in endemic taxa, and phylogenetic history summarizes these populational events. History of human activities chronicles alien interventions often of dramatic proportions with negative consequences for the native flora. Knowing these six histories allows a richer understanding of factors responsible for diversity, and how they have interacted (and continue to interact) in maintenance of diversity.