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The ecology of wild fruit persistence in Hong Kong

by Tang, Ming-chak

Abstract (Summary)
(Uncorrected OCR) Abstract of the thesis entitled

THE ECOLOGY OF WILD FRUIT PERSISTENCE IN HONG KONG

Submitted by

Tang Ming Chak

for the degree of Master of Philosophy at The University of Hong Kong

in March 2003

The relationships among wild fleshy fruits, frugivores, and fungi were investigated

in Hong Kong. Fleshy fruits must be attractive to vertebrate seed dispersal agents

while resisting microbial decay. Antimicrobial compounds on or in fruits are likely

to be unattractive to the seed dispersers, so a trade-off between antimicrobial

defense and palatability to dispersers may place limits on fruit persistence in nature.

The retention times of ripe fruits on 34 wild plant species under natural conditions

(unbagged persistence) and when fruits had been bagged with nylon mesh to

exclude frugivores (bagged persistence) were compared. Bagged persistence is a

measure of the effectiveness of fruit defense while unbagged persistence is an

inverse measure of attractiveness to vertebrate frugivores.

Bagged fruits persisted longer than unbagged fruits in 30 species. Fruits in half of

the species persisted for more than two months when bagged and for 6.8 months in

one species, Psychotria tutcheri. There was a significant relationship between the

mean persistence times of bagged and unbagged fruits, suggesting that species with

a high resistance to microbial infection are also less attractive to frugivores. Bagged

persistence times declined with increasing mean temperature during the persistence

period. Unbagged persistence times were longer in the forest understorey, which is

consistent with the low density of understorey frugivores. Among the fruit characters measured, total soluble carbohydrate content was negatively correlated and fibre content was positively correlated with bagged persistence. Mechanical damage significantly decreased the bagged persistence time for 47% of the species. Although some fruits decayed or dried up while attached to the plant, fruits of 53% of the species remained visually attractive to until they fell off.

Eighteen fruit specIes were examined for fruit-decaying fungi in nature. Surface-sterilized and non-sterilized fruits were incubated for 1-4 weeks and fungal fruiting bodies identified. A total of 540 fruit samples were examined; 495 fungal isolates obtained; and 102 microfungal taxa identified. Col/etotrichum and Phomopsis were the most frequently recorded fungal genera. flex cinerea fruits had the highest diversity of fungal assemblage, while Wikstroemia nutans supported the lowest diversity. Fifty-eight percent of fungal genera found in this survey have not been recorded previously on cultivated fruits. The fungal assemblage that developed on non-sterilized fruits after incubation was generally more diverse than on surface-sterilized fruits, but both were colonized mostly by non-specific fungi. Related fruit species did not, in general, have more similar fungal assemblages than unrelated species. The ability of detached fruits to resist fungal infection under incubation varied greatly, with 77% of fruits of Wikstroemia nutans still not infected after four weeks. Fungi were classified into three types: pathogens, latent opportunists and non-latent opportunists. Non-latent opportunists, such as Cladosporium, Fusarium and Penicillium, were the most prevalent on wild fruits.

Bibliographical Information:

Advisor:

School:The University of Hong Kong

School Location:China - Hong Kong SAR

Source Type:Master's Thesis

Keywords:fruit habitat china hong kong diseases and pests frugivores hina

ISBN:

Date of Publication:01/01/2003

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