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Title: Morphological and genetic variation in the genus Tetramesa and its parasitoids (Hymenoptera: Chalcidoidea) and its application to Iranian biogeography
Author: Madjdzadeh, Seyed Massoud
ISNI:       0000 0004 2745 8089
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2004
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The aim of this thesis was to investigate the evolution and ecology of parasitoid chalcidoid wasps associated with two allopatric grass species, Leucopoa pseudosclerophylla (Krivot.) Bor. and L. sclerophylla (Boiss. 8l Hohen.) V. Krecz & Bobrov in south-east, south-west and northern Iran. The associated chalcidoid wasp genus Tetramesa (=Isosoma Walk. -Harmolita Motsch.) (Hymenoptera: Chalcidoidea: Eurytomidae) is considered exclusively phytophagous during larval development with some species forming distinct galls and some live without any indication of a galling habit. Multidisciplinary approaches were used to clarify the morphological and molecular genetic variation of the chalcidoid wasps: 1) morphometries, 2) phylogenetic and phylogeographic relationships, 3) community structure. Morphometric analyses were carried out to study variation in morphological characters among geographic populations of Tetramesa spp. The northern populations feed on L. sclerophylla, while southern populations are restricted to L. pseudosclerophylla. Morphometric analyses of 19 characters showed that 4 and 5 of these characters displayed significant differences between populations of Tetramesa based on locality (3 sites) and region (3 sites) respectively. Discriminant function and cluster analyses showed the strongest distinction between geographic groups and exhibited geographically correlated variation in size for some morphological characters. The structure of the parasitoid communities associated with Tetramesa species in the two grass species was also explored. A semi-quantitative food web was constructed based on the total parasitism rates. The food web comprised two subcommunities, which contained IS species organized into five trophic levels. The most striking characteristic of the food web was the extreme specificity of most of the species in the community. The outcome of this high level of specialization was a compartmentalized food web. The result also showed that the parasitoids of most host species had relatively consistent dominant hierarchies. The genetic structure of the Tetramesa parasitoids, Eurytoma spp., Sycophila spp. (Eurytomidae), Pediobius spp. (Eulophidae), and Chlorocytus spp. (Pteromalidae) was investigated using sequence data from the mitochondrial cytochrome oxidase subunits (CO) I and II genes. Phylogeographic patterns of Sycophila spp. were investigated using a 778 base pair region of the COI gene which identified 5 haplogroups comprising 25 haplotypes in 10 populations. Considerable genetic variation and divergence was observed within and between haplogroups, especially haplogroups I and II which may comprise several new taxa. The sequence divergences within haplogroups ranged between 0.1 and 1.0% and among haplogroup values varied between 2.4 and 6.4%. Based on data from sequence divergence of other taxa and estimated divergence times it is hypothesized that divergence between haplogroups probably started from the late Pliocene and continued during the Pleistocene, probably in refugial areas followed by colonization events during interglacial periods.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available