Ecological parameters in a Bombina hybrid zone

• Main Author: Atkinson, Nick W.
• Published: University of Edinburgh 2001
• Subjects: 591.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.641128

Two transects across the hybrid zone between the fire bellied toads, <i>Bombina bombina </i> and <i>Bombina variegata</i> were studied. The first, near Pescenica in Croatia, had been the subject of a number of previous studies. The second, at Crna Mlaka, covered a wider region and its geography was more diverse. This thesis presents results of the first study to be undertaken in this part of the <i>Bombina</i> hybrid zone. Using data from the Pescenica transect, the cline for a single locus allomorphic enzyme trait was compared to that of the multi-locus trait for ventral colouration. A selection of ecological variables, extracted from a satellite image and a set of topographical maps, were examined for their effect on the position and width of the clines. The results were similar for both clines: the measure of forest cover extracted from the satellite image was found to give a significant improvement to the likelihood model of clines for both traits, with the multi-locus trait appearing to be more sensitive to ecological variation. The hybrid zone in the Crna Mlaka region was described and the position of a one dimensional cline for the ventral colouration trait estimated. The effect of ecological parameters altitude, contour density and forest cover were assessed, and it was established that the measure of contour density significantly improved the fitted model. This finding is in accordance with the hypothesis that movements of <i>Bombina bombina</i> are limited by the relief of the landscape rather than the absolute altitude.