The Genetic Composition of Philaenus spumarius Populations in Island Habitats Variably Affected by Voles

• Published in: Evolution 1975-12, Vol.29 (4), p.700-706
• Main Authors: Halkka, O., Raatikainen, M., Halkka, L., Hovinen, R.
• Format: Article
• Language: English
• Subjects: Animal morphology; Food plants; Ice; Meadows; Nymphs; Phenotypes; Population ecology; Population genetics; Population size; Voles
• ISSN: 0014-3820; 1558-5646
• DOI: 10.1111/j.1558-5646.1975.tb00863.x

Stability of allele frequencies in three color polymorphic island populations of the meadow spittlebug (Philaenus) was investigated in relation to the stability of the environment. One of the islands (Rovholmen) provided an environment which to the human eye remained practically unchanged throughout the study period, 1969-74. The color morph frequencies in the Philaenus population of this island showed great stability. On another island (Mellanspiken), the meadows constituting the habitat of Philaenus were very vulnerable to injury by the grazing and burrowing activities of field voles (Microtus), when these were present at high densities. Two Philaenus populations, A and B, were investigated in detail. Two of the six color polymorphism alleles originally present in A were lost at the bottleneck phase (1969-70) which coincided with the peak activity of the voles. This loss may be attributed to random genetic drift. Relief of molestation of the meadows by voles was followed by a quantitative and qualitative change in the food plant assortment available to the populations (A and B). The populations increased in size, and concomitantly the frequency of the most common color morph, typ, rose abruptly. The increase in typ frequency was probably due to density-dependent selection in which different phenotypes have dissimilar ecological requirements. On the third island investigated (Storlandsgrundet), the meadows were even smaller and even more liable to suffer from vole activities than meadows on Mellanspiken. On Storlandsgrundet, the Philaenus population was wiped out by the activities of Microtus, leaving meadows clear for subsequent immigrants to establish a new gene pool determined by the genotypes of these founders.