Persistence of British natterjack toad Bufo calamita Laurenti (Anura: Bufonidae) populations despite low genetic diversity

Abstract

Like other amphibians native to Britain, the natterjack toad Bufo cahmita must have colonized the islands during the relatively short period between the end of the last glaciation and the separation of Britain from mainland Europe by rising sea levels. Unlike the other native amphibians, however, E. cahmircl is a habitat specialist at the north-westerly edge of its biogeographical range and for most of the 8000-10000 years since its colonization has probably been restricted to open dunes, heathlands and upper saltmarshes, as isolated populations in a few discrete areas of the country. We have investigated the genetic diversity and relatedness of six widely separated British natterjack populations by allozyme analysis, and shown that all have very low diversity (Overall Pss% = 2.7%, H = 0.004) by comparison with other anurans, including natterjack populations in mainland Europe and common frogs (Rum temporaria, L) in Britain. Eighty percent of loci were fixed for the same allele in all six British natterjack populations and genetic differentiation between colonies was extremely low. The possible significance of these findings to the persistence of small isolated populations at range edges is discussed.

Phylogeography of the natterjack toad Bufo calamita in Britain: genetic differentiation of native and translocated populations

“…Microsatellite DNA has proved to be an appropriate marker system for quantifying genetic differentiation at the temporal and spatial scales relevant to the phylogeography of natterjack toads in postglacial Britain. By contrast, allozyme polymorphisms within British Bufo calamita populations proved too few for analyses of this kind, although they are much higher in central European natterjacks (Hitchings & Beebee 1996). The extra sensitivity inherent in potentially hypervariable microsatellite loci (Tautz 1989; Weber & May 1989) clearly facilitated genetic analysis of populations near the range edge, where variation in general is probably low but where there is also much of interest to ecology, evolution and conservation (Hoffmann & Blows 1994).…”

Viability analysis of a threatened amphibian population: modelling the past, present and future

“…Finally, as the low levels of genetic variation in this population imply low genetic resilience and little capacity to respond to environmental change, intensive management and protection are likely to remain especially important to the survival of species such as the natterjack, which are at their range edges (Hitchings and Beebee 1996). Key larval fitness attributes, notably growth rate and metamorph production, are substantially lower in small and isolated populations.…”

Developmental responses to pond desiccation in tadpoles of the British anuran amphibians (Bufo bufo, B. calamita and Rana temporaria)

“…One possibility is that such species have evolved traits that allow them to exploit transient habitats that are rich in food resources and low in competitors and predators. On the other hand, the British populations of B. calamita display remarkably little genetic variation compared to continental populations (Hitchings & Beebee, 1996). As Newman (1992) points out, for plasticity to evolve there must be genetic variation within the norm of reaction within a population.…”