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RESEARCH PRODUCT

The founder principle, founder selection, and evolutionary divergence and convergence in natural populations of Philaenus

subject

description

Parts of the archipelago of the Baltic Sea are rising above the water level at a steady, slow rate. Plant species appear on the emerging islands in a definite order, and an early stage and a late stage can be distinguished in the development of meadows on the islands. In 1969–1973 four populations of Philaenus spumarius living in meadows at the early stage had widely different frequencies of the alleles determining colour polymorphism. In the same years three Philaenus populations living on islands with meadows at the late stage had closely similar allele frequencies. The differences between the Philaenus populations in the early stage meadows are ascribed partly to the founder principle and to random genetic drift. There are indications, however, that founders are not entirely random but that founder selection may also occur. Increased age of populations appears to correlate with increased interpopulation similarity. The populations can be said to go through a divergence phase followed by a convergence phase. Part of the convergent evolution may be due to partial breakdown of isolation. Mainly, however, the convergence phase is a correlate of the increased uniformity of the late-stage meadows, as contrasted to the early-stage meadows.