Insect herbivores and neighbourhood effects in plant communities of Al Jabal Al Akhdar, Libya

Abdlrahman,, Abdlrahman Y.A. (2011) Insect herbivores and neighbourhood effects in plant communities of Al Jabal Al Akhdar, Libya. PhD thesis, University of Nottingham.

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Abstract

Neighbouring plants in the locale of an individual plant may help or hinder it in the task of defence against herbivores, depending on their levels of defence (chemical or physical), and their interactions with potential herbivores. Such ‘neighborhood effects’ are part of the complex network of species interactions that structure ecological communities. This thesis sets out to test whether there are neighbourhood effects on insect herbivory among the plants of the Al Jabal Al Akhdar region of Libya. Having chosen to concentrate on the two main species of three study sites, Juniperus phoenicea and Pistacia atlantica, nine plots were mapped in detail and the insect herbivores sampled from focal plants, and then from all plants. Leaves were sampled for chemical analysis of their phenol (tannin) content.

The set of insect herbivores collected from plants in the plots were identified to species using the expertise of the staff of the Natural History Museum in London. Some insects recorded are new to Libya, and there are several species not previously recorded as feeding on either of the two plant species studied.

Tannin levels were much higher in Pistacia than in Juniperus, and there were effects of elevation as well: plants from middle elevation plots had the highest levels, while those from the lowest elevation at the coast had the lowest levels of tannins.

There were clear effects of neighbouring plants on the insects of individual plants, in both Pistacia and Juniperus. These were much more complex effects in Pistacia, but both sets of predictors of insect herbivore density or species richness contained clear signs of neighbourhood effects, where the existence of close neighbours reduced the herbivore load on individual plants. There were no signs of any protective neighbourhood effects of tannin levels.

Thus in the plant communities of Al Jabal Al Akhdar, associational avoidance appears to be the major mechanism of neighbourhood effects, rather than associational resistance.

Item Type:Thesis (PhD)
Supervisors:Gilbert, F.S.
Eichhorn, M.P.
Faculties/Schools:UK Campuses > Faculty of Medicine and Health Sciences > School of Biology
ID Code:2122
Deposited By:Dr Abdlrahman Abdlrahman
Deposited On:26 Mar 2012 15:03
Last Modified:26 Mar 2012 15:03

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