New Zealand Journal of Botany abstracts

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Dispersal ecology of the lowland rain forest in the Vava'u island group, Kingdom of Tonga

Patricia L. Fall

School of Geographical Sciences
Arizona State University
Tempe, AZ 85287-0104, USA
fall@asu.edu

Taly Dawn Drezner

Department of Geography
N430 Ross
York University
4700 Keele Street
Toronto, ON M3J 1P3, Canada

Janet Franklin

Department of Biology
San Diego State University
San Diego, CA 92182-4614, USA

Abstract   We explore the dispersal ecology of the tropical lowland rain forest on the Vava'u island group, Kingdom of Tonga, to understand dispersal adaptations across successional vegetation types and by species origin. We utilise quantitative data on the relative plant abundance (basal area for overstorey and cover for understorey) of forest species from 64 600-m² vegetation plots on 13 islands. Frequencies of species by dispersal mechanisms permit comparisons according to community types, between understorey and overstorey taxa, and between endemic, indigenous, and exotic species (both Polynesian and European introductions).
   Birds and bats disperse 80% of the plant species in the lowland rain forests of Vava'u; water dispersal (40% of the species) is of secondary importance. Plants introduced by Polynesians comprise 5—10% of the rain forest overstorey; European introductions are common in the early successional forest, principally in the understorey. Over 30% of the indigenous trees in the late successional rain forest are potentially dispersed by rodents, but more likely these introduced (Polynesian and European) rats primarily act as seed predators.
   Plants in the lowland tropical rain forests of Vava'u are largely dispersed intra-island by birds and bats. While plants dispersed by epizoochory and human cultivation are encroaching in the early successional stages of the rain forest, perhaps the greater effect on these tropical forests may be seed predation by rodents, especially in late successional rain forest. Since the majority of the indigenous rain forest species are dispersed by native fauna, it is imperative that the extant birds and fruit bats of the Kingdom of Tonga continue to be preserved to maintain the regeneration of the rain forests on these relatively isolated oceanic islands.

Keywords   bat dispersal; bird dispersal; fruit bats; frugivory; lowland rain forest; seed dispersal; Tonga; tropical rain forest; Vava'u

B06040; Online publication date 22 May 2007; Received 6 October 2006; accepted 2 April 2007

New Zealand Journal of Botany, 2007, Vol. 45: 393—417
0028—825X/07/4502—0393 © The Royal Society of New Zealand 2007

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