Effective population size (Ne) is crucial parameter in evolutionary biology that reflects the number of individuals in a theoretically ideal population having the same magnitude of loss of genetic variation as the population in question. There are several types of Ne estimates, and they vary in definition and application. For example, contemporary Ne represents the size of a population in the previous generation/s and is a parameter of relevance in many species. Estimating contemporary N_e is, however, difficult and remains in practice often unknown. This is particularly the case for large populations where the amount of drift in the short term is limited. We used genomic data from 85 collared flycatchers of an island population sampled at two time points, and applied several methods to estimate Ne. These methods either compared genetic variation between the two time points (temporal methods) or analyzed variation patterns from a single time point (LD-based methods). The temporal methods estimated N_e at a level of few thousand, while the approach based on LD provided ambiguous estimates associated with high variance. Our results suggest that whole-genome data can help to estimate large contemporary N_e, but temporal sampling seems to be necessary.  

Article: Nadachowska-Brzyska K, Dutoit L, Smeds L, Kardos M, Gustafsson L, Ellegren H. 2021. Genomic inference of contemporary effective population size in a large island population of collared flycatchers (Ficedula albicollis). Molecular Ecology https://doi.org/10.1111/mec.16025.