One hundred and fifty one colonies of the ant L. acervorum comprising 815 queens were sampled in dry pine forest at nine sites in SE Sweden. 63°70 of the colonies contained more than one queen and of these 79% had more than one egg-laying (functional) queen, i.e. were polygynous. By using the electrophoretic variation at the PG1 locus a high overall relatedness (0.4) among queens from the same colony was found indicating that young queens are adopted by their mother nest. No spatial microdifferentiation in allele frequencies could be detected and it thus seems that despite restricted movements of queens there is a free gene flow in the populations.

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The deterministic maintenance of clonal diversity in thelytokous taxa can be seen as a model for understanding how environmental heterogeneity both can stabilize genetic diversity and can allow coexistence of competing species. We here analyze the temporal fluctuations in clonal diversity in the thelytokous Lonchopterid fly, Dipsa bifurcata (Fallé n, 1810), at four localities in Sweden over an 8-year period. Estimated fitness values for clones are cyclical, synchronous among populations and correlated with seasonal changes in the environment. Differential winter viability and emergence from overwintering along with differential reproductive rate during the summer appear to be the selective mechanisms by which long-term clonal diversity is maintained. In a companion paper (Tomiuk et al, 2004), we present a model for the maintenance of clonal diversity through the mechanism of differential diapause among clones, utilizing fitness values estimated from the data presented here. In general, our results imply that fluctuating seasonal fitnesses can maintain stable genetic polymorphism within populations, as well as coexistence between closely related competitors, when coupled with differences in diapause phenology. Keywords: clonal diversity; clonal coexistence; species coexistence; cyclical selection IntroductionFrom a population genetic perspective, genetic diversity in female parthenogenetic (or thelytokous) taxa can be studied as a simple model for examining the maintenance of genetic polymorphism. From an ecological viewpoint, the mechanisms determining the number of and interactions among sympatric thelytokous lineages (or clones, see below) can be seen as a limiting case for the study of niche subdivision of coexisting species (Parker, 1979;Vrijenhoek, 1979;Hebert and Crease, 1980;Jaenike et al, 1980). We here describe long-term dynamics of clonal diversity in Swedish populations of the thelytokous spearwinged fly, Dipsa bifurcata (Fallén, 1810) (Diptera: Lonchopteridae). Specifically, we analyze the temporal fluctuations in diversity and estimate fitness values from oscillations in clone frequencies at four localities in southern Sweden over an 8-year period. We show that these changes are cyclical, synchronous among populations in the same area and correlated with seasonal changes in the environment. In a companion paper (Tomiuk et al, 2004), we present a model for the maintenance of clonal diversity through the mechanism of differential diapause among clones, utilizing fitness values estimated from the data presented here. Taken together, our results strongly imply that fluctuating seasonal fitnesses among sympatric clones in a multivoltine species can maintain stable genetic diversity when coupled with clonal differences in diapause phenology.The temporal variation in D. bifurcata is reminiscent of the classical studies of chromosome inversion dynamics in Drosophila pseudoobscura Frolova (Diptera; Drosophilidae) (cf, Dobzhansky, 1943;Anderson et al, 1975). However, in Drosophila, and all sexual species, inv...

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