The Effect of Post-Metamorphic Dispersal on the Population Genetic Structure of Fowler's Toad, Bufo woodhousei fowleri

Abstract

A 4 yr mark and recapture study of Fowler's toad, Bufo woodhousei fowleri, determined the rate of post-metamorphic dispersal among seven breeding areas distributed linearly within a 2 km section of the Indiana Dunes National Lakeshore. Of more than 17,000 1 wk old tadpoles carrying a unique electromorph and introduced into the population and 8539 toads marked at metamorphosis, 37 animals were recaptured as breeding adults. Of these, 73% bred for the first time in natal ponds, most migrants moved only one or two breeding areas from the natal pond (24%), and one individual was observed migrating the maximum distance across the study site. These data combined with estimates of further dispersal in the adult stage and adult mortality yielded a per-generation migration rate among breeding areas of 49%. A Lincoln-Petersen estimate of the number of breeding adults and a direct count of egg masses produced upper and lower bounds on effective population size in each area of 152 and 38. These population sizes and migration rates were used in a computer simulation to estimate the standardized equilibrium genetic variance among populations. This analysis showed that local breeding aggregations of amphibians following similar patterns of migration are not closed genetic units and would not be expected to exhibit much genetic differentiation.