Reliable effective number of breeders/adult census size ratios in seasonal‐breeding species: Opportunity for integrative demographic inferences based on capture–mark–recapture data and multilocus genotypes

The ratio of the effective number of breeders (N_b) to the adult census size (N_a), N_b/N_a, approximates the departure from the standard capacity of a population to maintain genetic diversity in one reproductive season. This information is relevant for assessing population status, understanding evolutionary processes operating at local scales, and unraveling how life‐history traits affect these processes. However, our knowledge on N_b/N_a ratios in nature is limited because estimation of both parameters is challenging. The sibship frequency (SF) method is adequate for reliable N_b estimation because it is based on sibship and parentage reconstruction from genetic marker data, thereby providing demographic inferences that can be compared with field‐based information. In addition, capture–mark–recapture (CMR) robust design methods are well suited for N_a estimation in seasonal‐breeding species. We used tadpole genotypes of three pond‐breeding amphibian species (Epidalea calamita, Hyla molleri, and Pelophylax perezi, n = 73–96 single‐cohort tadpoles/species genotyped at 15–17 microsatellite loci) and candidate parental genotypes (n = 94–300 adults/species) to estimate N_b by the SF method. To assess the reliability of N_b estimates, we compared sibship and parentage inferences with field‐based information and checked for the convergence of results in replicated subsampled analyses. Finally, we used CMR data from a 6‐year monitoring program to estimate annual N_a in the three species and calculate the N_b/N_a ratio. Reliable ratios were obtained for E. calamita (N_b/N_a = 0.18–0.28) and P. perezi (0.5), but in H. molleri, N_a could not be estimated and genetic information proved insufficient for reliable N_b estimation. Integrative demographic studies taking full advantage of SF and CMR methods can provide accurate estimates of the N_b/N_a ratio in seasonal‐breeding species. Importantly, the SF method provides results that can be readily evaluated for reliability. This represents a good opportunity for obtaining robust demographic inferences with wide applications for evolutionary and conservation research.