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Links between ontogeny, chemical and physical characteristics of foliage and mammalian herbivory in Eucalyptus nitens

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Loney, Prue Elizabeth (2007) Links between ontogeny, chemical and physical characteristics of foliage and mammalian herbivory in Eucalyptus nitens. PhD thesis, University of Tasmania.

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Abstract

Throughout plant development from seeds to seedlings, juveniles and mature
stages a plant's palatability or resistance to herbivory is likely to change. Such
ontogenetic changes can be due to changes in chemical and physical
characteristics of the foliage. Consequently, herbivores often prefer to feed on
particular plant ontogenetic stages.
The research presented in this thesis focuses on the effects of plant ontogeny on
chemical and physical characteristics of Eucalyptus nitens foliage, and flow on
effects for mammalian herbivory by the common brushtail possum (Trichosurus
vulpecula), and the red-bellied pademelon (Thylogale billardierii). My research
demonstrates that large changes in foliage chemical and/or physical
characteristics occur during the early seedling stage, between young and old
leaves within seedlings, and between juvenile and adult leaves within 4-year-old
trees. Furthermore, evidence from feeding trials implies that these changes are
likely to be associated with changes in mammalian herbivory.
No single chemical or physical characteristic of the foliage could explain the
patterns of herbivory observed across the onto genetic stages studied. In fact,
certain chemical or physical characteristics affected foliage resistance to
mammalian herbivores at some ontogenetic stages but not at others.
Furthermore, the importance of particular chemical and physical characteristics
differed between brushtail possums and pademelons, and under the types of
conditions they were offered the foliage (i.e. no-choice and choice trials).
Chemical analyses suggested that newly emerged seedlings become more protected from mammalian herbivores as they increased in age, with chemicals
known to deter these herbivores (sideroxylonals and cineole) being present in
minute quantities at seedling emergence. Within seedlings, pademelons preferred
older leaves that contained the lowest concentration of sideroxylonals and
cineole, while possums generally preferred young leaves high in sideroxylonals
and cineole, but also high in nitrogen. Under choice conditions possums
preferred juvenile over adult tree foliage, while under no-choice conditions they
consumed as much adult foliage as juvenile. These results suggested that
difference in leaf toughness affected feeding preference under choice condition
but not under no-choice conditions.
Currently ecological and evolutionary theories regarding interactions between
plants and herbivores are largely based on studies conducted at a single
ontogenetic stage. However, the large effects of ontogeny on the chemical and/or
physical characteristics of the foliage and its palatability to herbivores shown in
this thesis emphasise Boege and Marquis' (2005) assertion that the role of
ontogeny should be an important component in plant defence theories.

Item Type: Thesis (PhD)
Keywords: Shining gum, Shining gum
Copyright Holders: The Author
Copyright Information:

Copyright 2007 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Available for library use only and copying in accordance with the Copyright Act 1968, as amended. Thesis (PhD)--University of Tasmania, 2007. Includes bibliographical references

Date Deposited: 19 Dec 2014 02:50
Last Modified: 17 Jul 2017 07:15
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