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Evolutionary Ecology

, Volume 24, Issue 5, pp 1219–1237 | Cite as

Independent hybrid populations of Formica polyctena X rufa wood ants (Hymenoptera: Formicidae) abound under conditions of forest fragmentation

  • Bernhard SeifertEmail author
  • Jonna Kulmuni
  • Pekka Pamilo
Original Paper

Abstract

Combined genetic and morphological data indicate frequent hybridisation between the wood ants Formica polyctena Förster 1850 and F. rufa Linnaeus 1761 in Central Europe. The genetic and morphological traits give a concordant picture of hybridisation with a strong correlation between the genotypic admixture proportions at 19 microsatellite loci and the first vectors of a principal component analysis (P < 0.001) and of a 3-class discriminant analysis (P < 0.001) of 15 quantitative morphological characters. This integrative approach enabled a grouping into F. polyctena, the hybrid and rufa. Genetic differentiation between the hybrid and F. rufa is significantly larger than between the hybrid and polyctena, indicating gene flow mainly between the latter entities. A suggested gene flow bias towards F. polyctena agrees with differential queen acceptance and mating behaviour. Both genetic and phenotypic colony parameters indicate predominance of monogyny in F. rufa but of polygyny in polyctena and the hybrid. Hybrids are intermediate between the parental species in body size, diagnostic morphological characters, monogyny frequency, size of nest population, nest diameter and infestation rate with epizootic fungi. The three entities respond differently to woodland fragmentation. Hybrids are significantly more abundant in forests with a coherent area <300 ha than in woodland above this size. Regions with high hybrid frequency in Germany—the Eastern Oberlausitz (23%) and the Baltic Sea islands Darss, Hiddensee and Rügen (28%)—are characterised by a fragmented woodland structure whereas regions with low hybrid frequency—Brandenburg and the lower Erzgebirge (3.4%)—have clearly larger and more coherent forest systems. Data from other European countries indicate habitat fragmentation to be a facilitating factor but no essential precondition for interspecific hybridisation in these ants. Hybrids are hypothesised to have selective advantage in fragmented systems because of combining the main reproductive and dispersal strategies of the parental species.

Keywords

Interspecific hybrids Habitat fragmentation Microsatellites Morphometry Integrative taxonomy 

Notes

Acknowledgments

We wish to thank Philip Attewell, Wouter Dekoninck, Dieter Bretz, Gennady Dlussky, Katrin Möller, Rainer Neumeyer and Roland Schultz for providing samples and Riitta Jokela for the laboratory analyses. Jaqueline Gitschmann helped with the transformation of air-photographs into a graphics. The work was supported by grants from the Academy of Finland (1122210 to P.P.).

Supplementary material

10682_2010_9371_MOESM1_ESM.pdf (68 kb)
(PDF 68 kb)

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Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  1. 1.Senckenberg Museum of Natural History GörlitzGörlitzGermany
  2. 2.Department of Biology and BiocenterUniversity of OuluOuluFinland
  3. 3.Department of BiosciencesUniversity of HelsinkiHelsinkiFinland

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