Genetic differentiation of the common toad (Bufo bufo) in the Swiss Alps

We analysed the genetic differentiation of tadpoles from 24 Swiss populatio ns of Bufo b. bufo and B. b. spinosus, using horizontal starch gel electrop horesis of eight enzymes coded by ten loci. For comparison, we included ten populations from more distant localities. Populations of Bufo calamita wer e included as outgroup. A very low level of genetic differentiation was fou nd among populations from the Alpine region, including B. b. bufo populatio ns from the Czech Republic and northern Germany, and B. b, spinosus populat ions from northern Italy. Genetic differentiation within populations was mu ch higher than differentiation among populations or regions. In contrast, t he southern French B. b. spinosus populations were clearly differentiated b y allele substitution at three out of ten loci scored. These alleles of the French populations, however, were also found in low frequencies in some po pulations from western Switzerland and Italy. This is interpreted to result from gene flow. Morphometric data of adult B, bufo (13 populations, 174 ad ult toads) turned out to be strongly size dependent. However, relative ann length and density of large warts ventral to the parotoids showed differenc es between the two subspecies.