Genetic structure in insular and mainland populations of house sparrows (Passer domesticus) and their hemosporidian parasites.
Small and isolated populations usually exhibit low levels of genetic variability, and thus, they are expected to have a lower capacity to adapt to changes in environmental conditions, such as exposure to pathogens and parasites. Comparing the genetic variability of selectively neutral versus functional loci allows one to assess the evolutionary history of populations and their future evolutionary potential. The genes of the major histocompatibility complex (MHC) control immune recognition of parasites, and their unusually high diversity is genes which is likely driven by parasite-mediated balancing selection. Here, we examined diversity and differentiation of neutral microsatellite loci and functional MHC class I genes in house sparrows (Passer domesticus), living in six insular and six mainland populations, and we aimed to determine whether their diversity or differentiation correlates with the diversity and the prevalence of infection of hemosporidian parasites. We found that island bird populations tended to have lower neutral genetic variability, whereas MHC variability gene was similar between island and mainland populations. Similarly, island populations tended to show greater genetic differentiation than mainland populations, especially at microsatellite markers. The maintenance of MHC genetic diversity and its less marked structure in the island populations could be attributed to balancing-selection. The greater MHC differentiation among populations was negatively correlated with similarity in blood parasites (prevalence and diversity of parasite strains) between populations. Even at low prevalence and small geographical scale, haemosporidian parasites might contribute to structure the variability of immune genes among populations of hosts.
Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France ; Laboratoire LBBE, UMR CNRS 5558, Université Claude Bernard Lyon 1 bâtiment Mendel, 43 boulevard du 11 novembre 1918, 69622, Villeurbanne Cedex, France.
Coraline
C
Bichet
Department of Zoology, University of Venda Private Bag X5050, Thohoyandou, 0950, South Africa ; Department of Integrative Biology and Evolution, Konrad-Lorenz-Institute of Ethology, University of Veterinarian Medicine Vienna Savoyenstr. 1a, A-1160, Vienna, Austria.
Yoshan
Y
Moodley
Department of Integrative Biology and Evolution, Konrad-Lorenz-Institute of Ethology, University of Veterinarian Medicine Vienna Savoyenstr. 1a, A-1160, Vienna, Austria.
Dustin J
DJ
Penn
Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France.
Gabriele
G
Sorci
Biogéosciences, UMR CNRS 6282, Université de Bourgogne 6 Boulevard Gabriel, 21000, Dijon, France.
Stéphane
S
Garnier
Genetic differentiation; Passer domesticus; genetic variability; haemosporidian parasites; insularity; major histocompatibility complex; microsatellites