Where have all the tadpoles gone? Individual genetic tracking of amphibian larvae until adulthood

Reliably marking larvae and reidentifying them after metamorphosis is a challenge that has hampered studies on recruitment, dispersal, migration and survivorship of amphibians for a long time, as conventional tags are not reliably retained through metamorphosis. Molecular methods allow unique genetic fingerprints to be established for individuals. Although microsatellite markers have successfully been applied in mark-recapture studies on several animal species, they have never been previously used in amphibians to follow individuals across different life cycle stages. Here, we evaluate microsatellites for genetic across-stages mark-recapture studies in amphibians and test the suitability of available software packages for genotype matching. We sampled tadpoles of the dendrobatid frog Allobates femoralis, which we introduced on a river island in the Nature Reserve 'Les Nouragues' in French Guiana. In two subsequent recapture sessions, we searched for surviving juveniles and adults, respectively. All individuals were genotyped at 14 highly variable microsatellite loci, which yielded unique genetic fingerprints for all individuals. We found large differences in the identification success of the programs tested. The pairwise-relatedness-based approach, conducted with the programs kingroup or ML-Relate, performed best with our data set. Matching ventral patterns of juveniles and adult individuals acted as a control for the reliability of the genetic identification. Our results demonstrate that microsatellite markers are a highly powerful tool for studying amphibian populations on an individual basis. The ability to individually track amphibian tadpoles throughout metamorphosis until adulthood will be of substantial value for future studies on amphibian population ecology and evolution.