Assessment of census (N) and effective population size (Ne ) reveals consistency of Ne single-sample estimators and a high Ne/N ratio in an urban and isolated population of fire salamanders

Amphibians are the most threatened vertebrates on Earth, and one of the main factors involved in their decline is the loss and fragmentation of their natural habitats. Contemporary urban development is a major cause of habitat fragmentation, and populations trapped within urban environments offer a unique opportunity to study effects of fragmentation. Here, we compared, for the first time in fire salamanders (Salamandra salamandra), estimates of census (N) and effective population size (N (e) ) in a small urban population in the city of Oviedo (Spain). We performed a 4 year capture-mark-recapture study and used three single-sample N (e) estimators based on 58 individuals genotyped for 15 polymorphic microsatellite loci. Our study showed a small ( salamanders; 95 % CI 100-142) but dense population (mean 0.45 individuals per m(2)), while single-sample estimators provided congruent N (e) estimates. A high N (e) /N population size ratio (range 0.50-0.84) obtained in this small and isolated population suggests the existence of mechanisms of genetic compensation (low reproductive variance and multiple paternity) in fire salamanders.