Abstracts (first author)
Spatio-temporal dynamics of genetic variation and effective population size in fragmented house sparrow populations
Habitat fragmentation is a major threat to biodiversity: by reducing population sizes and gene flow between populations it affects genetic structure and effective population size (Ne), which have important implications for population dynamics and evolutionary processes. We used natural house sparrow (Passer domesticus) populations in Norway as a model system to investigate if population type (i.e. mainland or island), geographic distance, adult population size (N), immigration rate and sex ratio explained intra- and interpopulation genetic variation and Ne of fragmented populations. Data from microsatellite genotyping across multiple populations and generations was used. Our results showed that intrapopulation genetic variation was lower and the occurrence of population bottlenecks more frequent on islands than the mainland, and the general level of genetic differentiation was higher between islands than between mainland populations, but only at shorter distances. Furthermore, genetic differentiation decreased, whereas intrapopulation genetic variation and Ne/N-ratios increased with immigration rates. Both intrapopulation genetic variation and Ne increased with population size. However, genetic Ne was much larger than demographic Ne (often even >N), probably due to a greater effect of immigration on genetic than on demographic processes. In constrast, genetic Ne for the metapopulation were within the expected range (<N), suggesting that in fragmented populations even low levels of gene flow may make the total metapopulation the appropriate scale of estimation. We also developed a genome-wide 10 000 Single Nucleotide Polymorphism (SNP) chip for the house sparrow and screened individuals from four populations. This demonstrated that genome-wide marker data gave results similar to microsatellites. Our results are relevant for a better understanding of evolutionary processes and hence conservation of threatened populations.