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Title: Adaptation and habitat preference in a hybrid zone between Bombina bombina and Bombina variegata in Croatia
Author: MacCallum, Catriona J.
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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This thesis describes a hybrid zone between two taxa of toads, Bombina bombina and Bombina variegata in north eastern Croatia. The two taxa can be distinguished at four diagnostic enzyme loci. Clines at these loci are highly concordant; there is strong disequilibrium and substantial heterozygote. Both linkage disequilibrium and heterozygote deficit are asymmetric, being greater on the bombina side than on the variegata side. Different habitats are identified across the zone and a strong association with the genotype of the populations sampled from them, is found. This relationship is consistent across the hybrid zone. The cline is best described by a model which incorporates both a difference in gene frequency between habitats and a width which varies from place to place. Mark recapture studies show extensive movement, which implies that the association between habitat and genotype is due to a habitat preference. Translocation experiments suggest that there is adaptation to the habitats. A habitat preference combined with mixing between habitats will inflate linkage disequilibrium over and above that expected from dispersal alone. Non-random mating and selection in relation to the environment will also contribute to the disequilibrium. As a result, inferences made using traditional cline models, where disequilibrium is mainly generated by dispersal, no longer apply. These results are very different to those made from a previous analysis of the Bombina hybrid zone in Poland. There the cline showed a smoother transition of genotypes and a sharper step in gene frequency at the centre of the cline. The differences to the transect described here can be accounted for by a habitat preference. A habitat preference has important implications for the mechanism of sympatric speciation since it will restrict gene flow between populations in different habitats.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available