Effective Population Size in Red‐Cockaded Woodpeckers: Population and Model Differences

Abstract

Loss of genetic variability in isolated populations is an important issue for conservation biology. Most studies involve only a single population of a given species and a single method of estimating rate of loss. Here we present analyses for three different Red‐cockaded Woodpecker (Picoides borealis) populations from different geographic regions. We compare two different models for estimating the expected rate of loss of genetic variability, and test their sensitivity to model parameters. We found that the simpler model (Reed et al. 1988) consistently estimated a greater rate of loss of genetic variability from a population than did the Emigh and Pollak (1979) model. The ratio of effective population size (which describes the expected rate of loss of genetic variability) to breeder population size varied widely among Red‐cockaded Woodpecker populations due to geographic variation in demography. For this species, estimates of effective size were extremely sensitive to survival parameters, but not to the probability of breeding or reproductive success. Sensitivity was sufficient that error in estimating survival rates in the field could easily mask true population differences in effective size. Our results indicate that accurate and precise demographic data are prerequisites to determining effective population size for this species using genetic models, and that a single estimate of rate of loss of genetic variability is not valid across populations.

European rabbit survival and recruitment are linked to epidemiological and environmental conditions in their exotic range

“…For instance, based on our research: (i) estimates of variation in vital rates (survival and recruitment) can be used to parameterize population models and simulate environmental stochasticity; (ii) the role of density-dependent processes and population-level disease infection rates can be modelled using a more informed approach; and (iii) a stronger understanding of the inter-play between environmental conditions and vital rates can be used to strengthen assessments of the potential impact climate change may have on rabbit abundance. Sensitivity analysis could be used to identify model parameters whose estimation is most critical for local population-level type studies (Reed et al 1993). Likewise regional validation could be used to determine whether important model parameters need to be refined to suit the local system.…”

A Vital Rate Sensitivity Analysis for Nonstable Age Distributions and Short-Term Planning

“…There have been multiple population viability analyses (PVAs) of red-cockaded woodpeckers that provided sensitivity analyses. For example, Reed et al (1993) used a model focusing on maintaining a minimum effective population size rather than maximizing population growth. Using perturbation analysis, they concluded that adult survival was the most-sensitive parameter to decreasing loss of genetic variation.…”

Erratum

“…For a given adult population, effective size likely would be considerably different if helpers participate in clutch production than if they do not. Estimates of effective size for red-cockaded woodpecker populations have assumed that the species is monogamous, that helpers do not participate in mating, and that extra-pair copulations with males outside the group do not occur (Reed et al 1988(Reed et al , 1993. It is possible that prior to fragmentation and decline of red-cockaded woodpecker populations, more helpers were present and may have participated in copulating with the breeding female.…”