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Title: Population genetics, genetic differentiation and ecological tolerance in gobies
Author: Wallis, G. P.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1981
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Horizontal starch gel electrophoresis and selective histochemical staining techniques were used to study genetic variation at 31 loci, (14 enzymes and 6 non-specific proteins) in 9 gobioid species, (7 Pomatoschistus ap., Knipowitschia caucasica, Neogobius melanostomus). Materials and methods used and the biology of the species are fully described. The tissue distribution and structure of enzymes are described and are consistent with other studies of teleosts. Frequency distributions for allele frequencies and heterozygosities are given, and a general positive correlation of individual locus heterozygosities is shown. Genotypic distributions conform well to Hardy-Weinberg expectations. A positive correlation is demonstrated between broad niche heterogeneity and overall genetic variability for the 9 species, providing evidence in favour of the environmental-amplitude variation hypothesis. P.minutus, P.lozanoi and P.norvegicus represent a closely related group of sibling species, but differ greatly in their ecological niches. A temporal survey of the two most closely related, P.minutus and P.lozanoi, was undertaken, but no parallel changes in allele frequencies were observed. Five F1 hybrids (c 0.3%) were observed on the criteria of four diagnostic loci, and one probable F2 hybrid. Gene frequency data from an Adriatic population of P.minutus are presented and intraspecific differentiation with referrence to a unique duplicate Idh locus is discussed. Selection experiments on the estuarine P.microps with regard to temperature and salinity parameters were inconclusive but suggest negative heterosis operating at the Psi locus in low temperature/high salinity regimes. A detailed study of intraspecific genetic differentiation between the nine species was made. Histograms and dendrograms are evolved from identity and distance data. Measures of genetic divergence agree well with the current taxonomy based on morphological criteria. The results are discussed in the light of contemporary evolutionary and population genetics theory.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available