Sexual Selection and Insect Genitalia

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Sexual Selection and Insect Genitalia

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dc.contributor.author Higgins, Sahran Louise en_GB
dc.date.accessioned 2009-10-01T16:47:45Z en_GB
dc.date.accessioned 2011-01-25T16:55:29Z en_US
dc.date.accessioned 2013-03-21T12:04:06Z
dc.date.issued 2009-06-08 en_GB
dc.description.abstract Sexual selection is generally accepted as being responsible for the rapid and divergent evolution of male genitalia and other primary reproductive characteristics in internal fertilisers, such as testes size and sperm length. Selection can act via three main processes: sperm competition, cryptic female choice and sexual conflict, however very few studies have directly addressed the patterns of selection, the degree of phenotypic and genotypic variability expected in genital morphology or the degree to which intromittent genitalia are dependent on male condition. The seedbug, Lygaeus equestris has greatly elongated intromittent genitalia, being almost as long the body. Here I determine whether this is a sexually selected trait and further assess the degree of genetic and phenotypic variability in the greatly elongated male intromittent organ in relation to other morphological components. Further to this, patterns of inheritance and allometry of such exaggerated genitalia were investigated, and of the degree of condition dependence of genital and general morphology was experimentally assessed by varying food availability during ontogeny. Finally, using experimental evolution, I manipulated the level of sexual selection by biasing adult sex-ratio (male-biased, equal-sex, female biased) and investigated potential correlated evolution of female reproductive morphology and fertile (eupyrene) and non-fertile (apyrene) sperm length and numbers in the Indian meal moth, Plodia interpunctella. The main findings indicated that genital length was sexually selected in L. equestris being negatively related to male fertilisation success and that there was great phenotypic variation in genitalia both across and within populations. Genital length was negatively allometric, in spite of being hugely elongated, and was significantly heritable with considerable evolvability. It was also evident that there was genetic variation in the condition dependence of genital length with a significant genotype-by-condition interaction and much reduced genetic variation in genital length in the poor food treatment. Male and female primary sexual traits of P. interpunctella were also shown to covary, but this pattern did not differ across treatments. Taken together, the results presented in this thesis do not support traditional hypotheses of genital evolution and instead suggests that male intromittent genital length of L. equestris is sexually selected in a similar way to secondary sexual characteristics. This is also true when examining primary sexual traits in P. interpunctella and further highlights the false dichotomy between primary and secondary sexual traits. en_GB
dc.description.sponsorship Natural Environment Research Council en_GB
dc.identifier.uri http://hdl.handle.net/10036/83254 en_GB
dc.language.iso en en_GB
dc.publisher University of Exeter en_GB
dc.rights.embargoreason Future publication of chapters en_GB
dc.title Sexual Selection and Insect Genitalia en_GB
dc.type Thesis or dissertation en_GB
dc.date.available 2011-12-01T05:00:04Z en_US
dc.date.available 2013-03-21T12:04:06Z
dc.contributor.advisor Wedell, Nina en_GB
dc.publisher.department Biosciences en_GB
dc.type.degreetitle PhD in Biological Sciences en_GB
dc.type.qualificationlevel Doctoral en_GB
dc.type.qualificationname PhD en_GB


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