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Mitochondrial and morphological variation populations of New World Screwworm fly, Cocchliomyia hominivorax

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Author(s):
Mariana Lúcio Lyra
Total Authors: 1
Document type: Doctoral Thesis
Press: Campinas, SP.
Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia
Defense date:
Examining board members:
Ana Maria Lima de Azeredo Espin; Vera Lucia da Silva Valente Gaiesky; Claudio José Von Zuben; André Victor Lucci Freitas; Jörg Kobarg
Advisor: Ana Maria Lima de Azeredo Espin; Louis Bernard Klaczko
Abstract

The New World screwworm fly, Cochliomyia hominivorax, is an important parasitic insect pest in Neotropical region, and represents a serious threat to the livestock sector. In this thesis we analyzed different aspects of molecular and morphological variation in the species, aiming to obtain a clear scenario about the extent and distribution of genetic diversity in C. hominivorax. The main contributions of this thesis are organized in two parts. The first one, composed of four different works, contains the results about mitochondrial DNA (mtDNA) diversity in the species. In the first work (Article 1), mtDNA was used to study the diversity and population structure of C. hominivorax in Uruguay; results indicated high mtDNA variability and suggested that in Uruguay species form a single panmitic population. In the second work (Article 2) we analyzed 34 populations of C. hominivorax in ten different countries of Caribbean and South America, encompassing almost all the current distribution of the species. Significant population structure and low variability were found in Caribbean populations; in contrast, high variability and low differentiation was found among mainland populations. Our results showed a complex pattern of population genetic structure for the species, suggesting that different processes are acting to the shaping and maintenance of the observed patterns. The third work in this part is about the characterization of length variation in the mtDNA control region; the variation was due to the existence of tandem repetitions of conserved sequence blocks in the control region and the observations suggested that repetitions may be independent events in each locality. The analysis of variable domain revealed high intra-specific polymorphism and suggested that this region may be a potential marker for the study of species populations. The fourth work analyses the relationship between Caribbean and mainland population; Cuban populations differs significantly from all others results suggested different colonization events for Caribbean region. The other part of this thesis consists of two works about characterization of wing variation. The first one (Article 3) provides a morphological analysis of wing variation of C. hominivorax and evaluate the potential use of this morphological character for population variation studies. We found a striking sexual dimorphism in the species for both wing size and shape and suggested that it reflects a history of different selection pressures operating on males and females. We also found morphological variation between populations, which were not associated with latitude or temperature; these preliminary results suggested that C. hominivorax morphology might be affected by locality and/or host characteristics. The second work is about wing variation between C. hominivorax and C. macellaria, results indicated that geometric morphometric methods are useful for species identification and that this strategy could be useful in monitoring invasions events in regions where species have been previous eradicated. Results of this part indicated that wing shape and size may be a reliable marker for population analyses of New World Screwworm, and for inter-specific analyses in genus Cochliomyia. (AU)