Habitat preference and selection in a Bombina hybrid zone

• Main Author: Sands, Timothy
• Published: University of Edinburgh 2005
• Subjects: 576.58
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.661573

This thesis describes novel data about reproductive isolation between the toad species <i>Bombina bombina </i>and <i>Bombina variegata </i>in a mosaic hybrid zone at Apahida in north-west Romania. The hybrid zone at Apahida forms a fine-scaled mosaic, with the genetic composition of subpopulations varying with the aquatic habitat, even over small distances. I conducted a mark-recapture study which showed that adults move between sites at a high rate and move over distances greater than those separating different habitat types. Variation between sites could be maintained with this movement pattern if there is habitat preference. I use mark-recapture data to test for evidence that adult <i>Bombina </i>are choosing their sites with a preference that correlates with allele frequency at neutral loci; the conclusions vary depending on the assumptions of the analysis. An adult habitat preference for mating site can result in the continuation of the habitat association in the next generation. I test for evidence of this in the genotypes of the resulting eggs, and find no evidence that habitat preferences create habitat associations. Morphology also varies between habitats. I examine the distribution and association of quantitative traits across the hybrid zone. This demonstrates that considerable dispersal occurs from sites whose populations are most similar to the pure species to sites of intermediate phenotype. It also provides some evidence that pure species combinations of these traits are favoured over mixed combinations. These results show that the habitat association of adult <i>Bombina </i>may not be as important in preventing introgression as it would first appear. However it also reveals that major changes to the composition of populations occur between egg laying and adulthood, changing the frequency of neutral alleles and generating linkage disequilibria and a deficit of heterozygotes.