|Year of Publication:
|allozymes, aphodius, gene flow, genetic differentiation, mitochondrial DNA, spatial population structure
The dynamics and evolution of populations will critically depend on their spatial structure.Hence, a recent emphasis on one particular type of structure—the metapopulation conceptof Levins—can only be justified by empirical assessment of spatial population structuresin a wide range of organisms. This paper focuses onAphodius fossor, a dung beetle specializedon cattle pastures. An agricultural database was used to locate nearly 50 000 localpopulationsofA. fossorin Finland. Several independent methods were then used to quantify key processesin this vast population system.Allozyme markers and mitochondrial DNA (mtDNA)sequences were applied to examine genetic differentiation of local populations and to deriveindirect estimates of gene flow. These estimates were compared to values expected on thebasis of direct observations of dispersing individuals and assessments of local effectivepopulation size. Molecular markers revealed striking genetic homogeneity inA. fossor.Differentiation was only evident in mtDNA haplotype frequencies between the isolatedÅland islands and the Finnish mainland. Thus, indirect estimates of gene flow agreed withdirect observations that local effective population size inA. fossoris large (hundreds ofindividuals), and that in each generation, a substantial fraction (approximately one-fifth) ofthe individuals move between populations. Large local population size, extreme haplotypediversity and a high regional incidence ofA. fossorall testify against recurrent populationturnover. Taken together, these results provide strong evidence that the whole mainlandpopulation ofA. fossoris better described as one large ‘patchy population’, with substantialmovement between relatively persistent local populations, than as a classical metapopulation.