The Effect of Management on Effective Population Size in the Arctic Fox (Vulpes lagopus) Metapopulation in Scandinavia.

Abstract

Estimates of effective population size (Ne) may provide insight to patterns of changes in allele frequencies and heterozygosity in a population. Furthermore, by estimating Ne, one can predict future changes in genetic diversity because N_e determines the rate of random genetic drift. Ne is usually smaller than the census population size, Nc, typically ranging from 0.25 0.75 in vertebrate species, most often below 0.5. In this study, two approaches were applied to estimate N_e in three arctic fox populations in Scandinavia from 2008 to 2015. I used several genetically based methods and a method based entirely on demographic data. The Scandinavian arctic fox has been protected for more than 80 years. Around year 2000, implementation of conservation actions were initiated as a part of the national action plans for the arctic fox, which have been intensified since 2007. Over the study period, there was an increase in Nc, closely linked to the implemented management actions, applied at different intensity in the three subpopulations. In general, my results showed that there was an increase in the Ne in all three subpopulations, and further an increase in the ratio of effective to - census population size (Ne/Nc) from the implementation of management actions and throughout the study period. For the genetic single sample method, the estimates with higher sample size appeared relatively reliable, whereas years with smaller sample size had estimates with larger confidences intervals. Using genetic methods with multiple samples, several generations between each sample gave more reliable estimates. The same was found when samples sizes were larger. The demographic estimator was sensitive to small sample size causing unreliable estimates of survival and reproduction within each sex and age class. The demographic estimates of Ne, together with estimates of the Ne values from the genetic single sample and temporal methods, indicated a positive response to the conservation actions that have been carried out in all three study populations. However, in 2015, the arctic fox subpopulations have still not reached a viable population size and hence continued actions are needed. Nevertheless, the observed increase in the Ne/Nc ratio within each subpopulation and the metapopulation over the last decade, may suggest an improved chance for persistence of the Scandinavian arctic fox population in the future.