Abstract
Early detection of population declines is essential to prevent extinctions and to ensure sustainable harvest. We evaluated the performance of two Ne estimators to detect population declines: the two-sample temporal method and a one-sample method based on linkage disequilibrium (LD). We used simulated data representing a wide range of population sizes, sample sizes and number of loci. Both methods usually detect a population decline only one generation after it occurs if Ne drops to less than approximately 100, and 40 microsatellite loci and 50 individuals are sampled. However, the LD method often out performed the temporal method by allowing earlier detection of less severe population declines (Ne approximately 200). Power for early detection increased more rapidly with the number of individuals sampled than with the number of loci genotyped, primarily for the LD method. The number of samples available is therefore an important criterion when choosing between the LD and temporal methods. We provide guidelines regarding design of studies targeted at monitoring for population declines. We also report that 40 single nucleotide polymorphism (SNP) markers give slightly lower precision than 10 microsatellite markers. Our results suggest that conservation management and monitoring strategies can reliably use genetic based methods for early detection of population declines.
Highlights
Managers of threatened populations faces the challenge of early and reliable detection of population declines
With a fixed initial effective population size (N1) of 600 and a population decline to an N2 of 50, we could detect a reduction of N^e from the original N1 after only one generation in 80% or more cases for each method when sampling just 25 individuals and 20 microsatellite loci
Our results show that early detection and reliable sizeestimation of population declines is increasingly possible using genetic monitoring and estimators of effective population size
Summary
Managers of threatened populations faces the challenge of early and reliable detection of population declines. Detection of populations that have suffered a decline will allow for a broader and more efficient range of management actions (e.g. monitoring, transplanting, habitat restoration, disease control, etc.) which will reduce extinction risks. Genetic methods can be used to estimate effective population size (Ne) and monitor for population declines (Leberg 2005). The most widely used genetic method for short-term (contemporary) Ne estimation (Krimbas and Tsakas 1971; Nei and Tajima 1981; Pollak 1983) is based on obtaining two samples displaced over time (generations) and estimating the temporal variance in allele frequencies (F) between them. The most widely used genetic method for short-term (contemporary) Ne estimation (Krimbas and Tsakas 1971; Nei and Tajima 1981; Pollak 1983) is based on obtaining two samples displaced over time (generations) and estimating the temporal variance in allele frequencies (F) between them. Luikart et al (1999) demonstrated that the temporal method was far more powerful than tests for a 2010 Blackwell Publishing Ltd 4 (2011) 144–154
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