Molecular analysis of subterranean detritivore food webs

Read, Daniel Steven 2007. Molecular analysis of subterranean detritivore food webs. PhD Thesis, Cardiff University.

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Abstract

Insect- and mollusc-parasitic nematodes are widely used for the biological control of soil-dwelling pests. Despite being used successfully to control a broad range of pest species in a variety of different crops, there have been many examples of pest control failures. Although the abiotic factors that influence the short-term persistence of nematodes are well understood, there is a lack of knowledge about the biotic factors. PCR-probes were designed and tested for the detection of three species of mollusc- and insect-parasitic nematodes: Phasmarhabditis hermaphrodita, Heterorhabditis megidis and Steinernema feltiae. These probes were used successfully to amplify nematode DNA from the gut of microarthropod predators. Potential sources of error and variation in prey detection times were tested and quantified, including nematode phoresy, scavenging, changes in temperature and predator body size. Field trials and molecular screening were used to identify predators of nematodes in the field, including the surface-dwelling collembola Isotoma viridis and Isotomurus palustris. Positive numerical responses by the surface-dwelling collembola indicated that immigration into nematode-sprayed (and hence food-rich) habitats was occurring. Terminal Restriction Fragment Length Polymorphism (T-RFLP) was tested for monitoring the effects of nematode biopesticide application on soil-dwelling nematode abundance and community structure. Using this technique, it was possible to create a nematode 'community profile'. Furthermore, it was possible, using T-RFLP, to identify changes in the nematode community after the application P. hermaphrodita to the soil. The nematode-specific PCR primers were used in conjunction with primers designed to amplify DNA from mollusc and insect hosts, including Deroceras reticulatum, Tenebrio molitor and Steinernema feltiae. Using these primers, it was possible to detect nematode parasitism within the host and intraguild predation by the carabid Pterostichus melanarius on infected hosts. Choice-test feeding trials with P. melanarius were used to investigate the production of antifeedants by the nematode-bacterium complex within the host are widely used for the biological control of soil-dwelling pests. Despite being used successfully to control a broad range of pest species in a variety of different crops, there have been many examples of pest control failures. Although the abiotic factors that influence the short-term persistence of nematodes are well understood, there is a lack of knowledge about the biotic factors. PCR-probes were designed and tested for the detection of three species of mollusc- and insect-parasitic nematodes: Phasmarhabditis hermaphrodita, Heterorhabditis megidis and Steinernema feltiae. These probes were used successfully to amplify nematode DNA from the gut of microarthropod predators. Potential sources of error and variation in prey detection times were tested and quantified, including nematode phoresy, scavenging, changes in temperature and predator body size. Field trials and molecular screening were used to identify predators of nematodes in the field, including the surface-dwelling collembola Isotoma viridis and Isotomurus palustris. Positive numerical responses by the surface-dwelling collembola indicated that immigration into nematode-sprayed (and hence food-rich) habitats was occurring. Terminal Restriction Fragment Length Polymorphism (T-RFLP) was tested for monitoring the effects of nematode biopesticide application on soil-dwelling nematode abundance and community structure. Using this technique, it was possible to create a nematode 'community profile'. Furthermore, it was possible, using T-RFLP, to identify changes in the nematode community after the application P. hermaphrodita to the soil. The nematode-specific PCR primers were used in conjunction with primers designed to amplify DNA from mollusc and insect hosts, including Deroceras reticulatum, Tenebrio molitor and Steinernema feltiae. Using these primers, it was possible to detect nematode parasitism within the host and intraguild predation by the carabid Pterostichus melanarius on infected hosts. Choice-test feeding trials with P. melanarius were used to investigate the production of antifeedants by the nematode-bacterium complex within the host.

Item Type:	Thesis (PhD)
Status:	Unpublished
Schools:	Biosciences
Subjects:	Q Science > QH Natural history > QH301 Biology
ISBN:	9781303182174
Funders:	BBSRC
Date of First Compliant Deposit:	30 March 2016
Last Modified:	10 Jan 2018 04:30
URI:	https://orca.cardiff.ac.uk/id/eprint/55689

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