Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.651641
Title: The impact of tropical forest disturbance and conversion on insect diversity in Costa Rica, Central America
Author: Gormley, Lorraine H. L.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2001
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Abstract:
The effects of anthropogenic forest disturbance on leaf litter invertebrates are investigated in a fragmented landscape in northern Costa Rica, Central America. Altogether, 16845 ants (Hymenoptera: Formicidae) and 1877 beetles (Coleoptera) were sampled from 500 pitfall traps. Samples were collected over a gradient of human disturbance with two field sites being located in each of the following land uses: primary forest (as a control), logged primary forest, secondary forest, Gmelina arborea plantation and cattle pasture. There were marked gradients in microclimate and vegetation structure over the gradient. Ants were collected from five subfamilies and beetles from 26 families. Both ant and beetle species composition and abundance changed with land use. Ants were significantly more abundant in pasture than in all other land uses, whereas beetle abundance was greatest in logged primary forest and primary forest and lower in all other land uses. Ant and beetle species richness was also significantly different between land uses, with the two invertebrate groups demonstrating similar patterns of change over the gradient. Examination of b - diversity revealed lower similarity between control sites and sites of greater disturbance. Patterns of species composition were analysed for the ant and beetle assemblages, and cluster analyses using Morisita's Index showed clear groupings by land use and degree of human intervention. TWINSPAN analyses revealed the varying species responses to forest disturbance. Many species of ants and beetles were found to be specific to particular land uses or groups of land uses. These 'indicator species' may be useful in future assessments of forest disturbance. Disturbance effects on species composition were mediated by six important environmental and physical variables: tree species diversity, litter biomass, soil temperature, soil pH, soil organic matter, altitude and slope. Multivariate analyses revealed the importance of soil organic matter levels, tree species diversity and litter biomass in defining the primary and logged forest ant and beetle assemblages, while changes in soil temperature and soil pH were shown to be important factors in defining the plantation and pasture assemblages.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.651641  DOI: Not available
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