Quantifying Acacia defences : understanding the role of hooks, spines and architecture

The effectiveness of the structural defences of Acacias vary within and between species as a result of differences in thorn type (hooks versus spines) and branching architecture. This study aims to develop methods for quantifying the effectiveness of defences, thereby allowing for comparisons between individuals and localities. Measurements of a range of thorn and branching parameters of eight Acacia species were used to calculate three indices (stripping, biting and branching) describing different components of Acacia structural defences. These were combined to form an overall defence index that was tested against the results of three feeding simulation tests as well as actual animal feeding rates obtained from trials using nyala held in bomas. The stripping, biting and branching indices were shown to provide a good measure of the different components of a structural defence, although the scaling of their contribution to an overall defence index is complicated by variation in the suite of browsers and the resources available at a locality. The indices developed in this study provide a useful tool for assessing the role of large mammal herbivory in different environments when attempting to understand variation in the life history strategies of Acacias.

Grantor dc:publisher.institution

Department of Biological Sciences

Year dc:date.issued

2004

Author dc:creator

• Hempson, Gareth

Advisors dc:contributor.advisor

• Kruger, Laurence
• Bond, William J
• Midgley, Jeremy J

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/11427/26121

OAI identifier oai:identifier

oai:open.uct.ac.za:11427/26121