EFFECTIVE NUMBER OF BREEDING ADULTS IN BUFO-BUFO ESTIMATED FROM AGE-SPECIFIC VARIATION AT MINISATELLITE LOCI

Estimates of the effective number of breeding adults were derived for three semi-isolated populations of the common toad Bufo bufo based on temporal (i.e. adult-progeny) variance in allele frequency for three h ighly polymorphic minisatellite loci. Estimates of spatial variance in allele frequency among populations and of age-specific measures of ge netic variability are also described. Each population was characterize d by a low effective adult breeding number (N-b) based on a large age- specific variance in minisatellite allele frequency. Estimates of N-b (range 21-46 for population means across three loci) were approximate to 55-230-fold lower than estimates of total adult census size. The im plications of low effective breeding numbers for long-term maintenance of genetic variability and population viability are discussed relativ e to the species' reproductive ecology, current land-use practices, an d present and historical habitat modification and loss. The utility of indirect measures of population parameters such as N-b and N-e based on time-series data of minisatellite allele frequencies is discussed r elative to similar measures estimated from commonly used genetic marke rs such as protein allozymes.