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

Abstract

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.

Mountains as barriers to gene flow in amphibians: Quantifying the differential effect of a major mountain ridge on the genetic structure of four sympatric species with different life history traits

“…Laguna de Valdemanco and other secondary breeding sites nearby were surveyed on a yearly basis since 2010, with multiple CMR sessions performed every year. In each CMR session, all sexually mature individuals found during visual encounter surveys were captured, sexed based on morphological characters and marked with passive integrated transponder (PIT) tags (further details in Sánchez‐Montes, Wang, Ariño, Vizmanos, & Martínez‐Solano, ). During this 7‐year period, we performed 219 CMR sessions and marked 1,086 adult E. calamita (427 of them were further recaptured in at least one subsequent CMR session, with a maximum of 23 recaptures per individual), 599 H. molleri (153 further recaptured, maximum: seven recaptures) and 662 P. perezi (325 further recaptured, maximum: 10 recaptures).…”

“…From that dataset, we excluded sample localities containing fewer than six non‐full‐sib individuals to avoid unreliable inferences derived from few full‐sib families in some genetic samples (Anderson & Dunham, ; Rodríguez‐Ramilo & Wang, ; Sánchez‐Montes, Ariño, et al., ). We also excluded Laguna de Valdemanco from the dataset because tissue sampling in that locality was more exhaustive than in other populations (Sánchez‐Montes, Wang, et al., ). Additionally, we obtained larval samples of P. cultripes in 13 localities across the study area (total n = 368, between 20 and 31 individuals per population, Table , Figure ) following the survey method described in Sánchez‐Montes, Ariño, et al.…”

Determinants and Consequences of Dispersal in Vertebrates with Complex Life Cycles: A Review of Pond-Breeding Amphibians

“…Ponds have abiotic (e.g., hydroperiod, temperature) and biotic (e.g., intra-and interspecific competition, predation) characteristics that affect offspring development and survival before metamorphosis (see the section titled Maternal and Environmental Carryover Effects in Dispersal-Related Traits). Furthermore, ponds host groups of breeders whose size and attributes (i.e., relatedness level, interindividual heterogeneity in reproductive output) vary over space and time (Cayuela et al 2017b;Sánchez-Montes et al 2017). The size of the pond, its isolation, and the level of philopatry of individuals modulate the risks of kin competition and inbreeding (Ronce 2007;Broquet and Petit 2009;Lowe and Allenford 2010).…”

Contrasting demographic trends and asymmetric migration rates in a spatially structured amphibian population

“…The effective size is generally lower than the population size because of the variance in the genetic contribution of individuals to the next generation (Frankham 1995). A high N e /N ratio (close to a value of 1) indicates that most adults in the population contribute to the next generation, whereas a low ratio implies a high variance in breeding success among adult individuals, leading to a potentially faster genetic impoverishment compared to populations with higher N e /N ratios (Ferchaud et al 2016;Sánchez-Montes et al 2017b).…”