Browsing by Author "Bunney, Katherine"

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    A comparison of the seed dispersal service offered by chimpanzees (Pan troglodytes) and gorillas (Gorilla gorilla)
    (2005) Bunney, Katherine; Bond, William J
    The handful of studies that have investigated chimpanzee and gorilla seed-dispersal identify these primates as important dispersal agents. These studies do not, however, make any measure of the 'quality' of the dispersal service offered by chimpanzees and gorillas. Determining 'quality' requires a measure of the dispersal distance and the microsite to which the seeds are dispersed. In this study, I report the first estimate of seed dispersal curves for chimpanzees and gorillas. Seed dispersal curves were produced by combining ape movement data with gut passage curves from literature. The derived dispersal distances for chimpanzees and gorillas are similar c. 7.7 km; this is surprisingly large when compared with other seed dispersal agents. This is likely due to a combination of foraging behaviour and gut physiology. At a species level, chimpanzees (Pan troglodytes) were shown to direct dispersal of Uapaca palidosa to favourable microsites even though gorillas (Gorilla gorilla) were responsible for moving a greater number of seeds. This study presents a novel method for the rapid derivation of dispersal curves and highlights the importance of incorporating species. level as well as community level studies to assess the quality of seed dispersal agents. It is my hope that the methods presented here be applied elsewhere so that the role of extant megaherbivores as seed dispersal agents be incorporated into future models that investigate forest dynamics.
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    Seed dispersal in South African trees: with a focus on the megafaunal fruit and their dispersal agents
    (2014) Bunney, Katherine; Bond, William J
    Seed dispersal is a key process. It is important in plant population biology because it influences the fate of seeds and the probability of recruitment, in plant biogeography since dispersal mode can influence the distribution range and rate of response to environmental change and habitat fragmentation, and in animal ecology since fruits can be an important dietary item (Wang and Smith, 2002). The majority of trees in the tropics (70 – 90%) and a large proportion of trees in temperate regions (up to 60%) rely on vertebrates for their dispersal (Howe and Smallwood, 1982; Fleming et al., 1987, Willson, 1990). Vertebrate dispersers range in size from 5g mistletoe birds (Dicaeidae) to 7,500,000g elephants (Elephantidae). The range and distribution of frugivore sizes is not uniform across ecosystems or geographical regions (Mack, 1993). These differences, one might suspect would be mirrored in the range and distribution of fruit size. This is not the case; in South America where the largest frugivorous mammal is the tapir (300kg; Hansen and Galetti, 2009), there is a subset of fruit that are conspicuously large. The paradoxical existence of such large fruit in the lowlands of Costa Rica was first noted by Janzen. In collaboration with Pleistocene faunal expert Paul Martin they conjectured that these fruit were ecological anachronisms that had evolved in the presence of large terrestrial vertebrates (>1000kg - megafauna) but had remained long after their demise (Janzen and Martin, 1982).