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The impact of Major Histocompatibility Complex composition on fitness and life history traits of a vertebrate model, the guppy (Poecilia reticulata)

Smallbone, Willow 2017. The impact of Major Histocompatibility Complex composition on fitness and life history traits of a vertebrate model, the guppy (Poecilia reticulata). PhD Thesis, Cardiff University.
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The Major Histocompatibility Complex (MHC) is a multi-gene family that includes most vertebrate immune genes. Life history traits have been associated with MHC allelic variation, including offspring survival, reproductive success, kin recognition, inbreeding avoidance, body mass gain, mate choice and parasite resistance. The studies reported in this thesis used laboratory and field investigations to identify differences in MHC genetic variation between truly wild, wild type and domesticated conspecifics and the implications of this for fitness, across the entire life history of a vertebrate, the guppy (Poecilia reticulata). Specifically, the effects of host inbreeding and domestication on parasite susceptibility are assessed in relation to MHC allelic and supertype composition. Laboratory studies showed that inbreeding and domestication lead to increased susceptibility to Gyrodactylus turnbulli, which was also linked to the presence of particular functional groups of MHC. A multi-site field sampling supported this finding; revealing that natural parasite communities reflected host MHC functional groups, as well as the river of origin. Truly wild fish had greater MHC genetic diversity than wild type (wild population maintained in the laboratory for ~ 3 years), which, in turn, were more genetically diverse than ornamental (domesticated) conspecifics. The accidental and deliberate release, into the wild, of domesticated fish is common. The release of infected and uninfected ornamental guppies into a wild type laboratory population increased parasite prevalence and abundance, due to the integration of a more susceptible individual into the social group. Mate preference is often linked to MHC similarity, whereby individuals select mates that are dissimilar or optimally similar at the MHC. The effects of sexual selection, MHC similarity and parasitism on mate choice, were assessed, indicating that a combination of factors are important in a female’s preference. Female guppies spent more time interacting with males with redder colouration and less MHC alleles in common. An experimental F1 generation revealed that offspring with parents sharing more MHC alleles and supertypes were more susceptible to parasitic infection. This research suggests that MHC functionality is at least as important as allelic and supertype diversity, with regards to individual fitness and life history traits.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > QH Natural history > QH301 Biology
Q Science > QH Natural history > QH426 Genetics
Q Science > QL Zoology
Funders: Leverhulme Trust
Date of First Compliant Deposit: 11 January 2018
Last Modified: 20 May 2021 08:19

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