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Phylogenetic and phylogeographic relationships of Pediobius furvus (Hymenoptera:Eulophideae) populations in West Africa

Shamie, Ibrahim Mangha Okeke 2004. Phylogenetic and phylogeographic relationships of Pediobius furvus (Hymenoptera:Eulophideae) populations in West Africa. PhD Thesis, Cardiff University.

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In spite of introduction of new improved and disease resistant cultivars of maize to Africa by the International Institute for Tropical Agriculture (IITA) high quality maize production remains hindered by insect pests, notably lepidopterous stem borers. Field trials using classical biological control methods are currently under way. These pests may be naturally kept in balance by cryptic parasitoid wasps, one of which is the topic of this thesis. Pediobius furvus Gahan (Hymenoptera: Eulophidae) is a gregarious pupal parasitoid of Sesamia calamistis, Chilo partellus and Busseola fusca. The targeted application of this parasitoid is a potentially important element of an integrated pest management strategy for African maize stem-borer control, yet we know very little about its biology, especially its population structure and diversity with respect to geography and host-relationship. Six populations were sampled across Africa. Experiments were carried out to examine morphological differentiation among the populations, to ask whether geographic variation supports their biological identity, and to investigate genetic variation and phylogenetic structure within and among populations. Thirteen morphological characters were examined on 120 females. Morphological characters measurements were used as descriptive data and were analysed using morphometric techniques. Results obtained based on differences among populations due to differences between individuals within populations placed populations in three groups and recognised one of the groups as separate. Mate recognition experiments were carried out with three UK species of Pediobius eubius complex {Pediobius deschampsiae Dawah, P. phalaridis Dawah and P. calamagrostis Dawah, and their Tetramesa hosts (Hymenoptera: Eurytomidae) as a model for test of different species compatibility. No female offspring was recovered from 2-species mating in all tests, whereas females were recovered from single-species mating. Field and laboratory tests results showed that the three species were reproductively incompatible in spite of living in sympatry. Behavioural isolation was due to courtship failure between male and female of different species. Molecular data were analysed from the same six African populations of P. furvus. Phylogenetic relationships among populations were explored using DNA sequence data from the nuclear large ribosomal subunit (28S) and the mitochondrial cytochrome b genes. Phylogenetic analyses at, above and beneath the putative species levels were carried out using minimum evolution model for both 28S rDNA and cytochrome b. An absence of large scale, but trend towards smaller-scale geographic structure was found using analysis of molecular variance of putative cytochrome 6 sequences. However, the sequences were found to be homologous.

Item Type: Thesis (PhD)
Status: Unpublished
Schools: Biosciences
ISBN: 9781303201172
Funders: Crop Protection Service of the Ministry of Agriculture, and the Sierra Leone government, International Institute for Tropical Agriculture, the Africa-Wide Biological Control Centre, WAFRINET (BioNET -International), Cardiff School of Biosciences
Date of First Compliant Deposit: 30 March 2016
Last Modified: 10 Oct 2017 15:29

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