Conservation genetics of an island toad: Bufo bufo in Jersey

On Jersey (British Channel Islands), common toads often reproduce in small, urban ponds. This atypical breeding strategy has implications for their persistence and they have declined on the island in recent times. We used polymorphic microsatellite markers to compare genetic diversity in Bufo bufo from five different ponds in Jersey with two populations from north-west France. Genetic diversity of Jersey toads was comparable with that of populations elsewhere in Europe. Numbers of breeding female toads in Jersey were correlated with pond area but estimators of genetic diversity were unrelated to pond area or female numbers. Fst estimates and isolation by distance tests indicated that there is little gene flow between breeding sites on the island. Jersey populations last shared a common ancestor with those of north-west France long before the island's physical separation about 6000 years ago. Toads have a long history in Jersey and were once probably very numerous there. The average effective historical population size of Jersey toads is estimated to be 15,000-16,000. Although genetic diversity of Jersey B. bufo is currently quite high, recent developments on the island may threaten this situation in the near future.