GENETIC DIFFERENTIATION OF DISJUNCT POPULATIONS OF THE ANTS FORMICA-AQUILONIA AND FORMICA-LUGUBRIS IN EUROPE

The species Formica aquilonia and F. lugubris of the mound-building re d wood ants have a disjunct boreoalpine distribution in Europe. The po pulations of F. aquilonia in Finland, Switzerland and the British Isle s show little genetic differentiation, whereas the populations of F. l ugubris show considerable differentiation. The Central European popula tions morphologically identified as F. lugubris can be genetically div ided into two groups (here called types A and B). Type B is found in t he Alps and the Jura mountains, and is genetically inseparable from F. aquilonia. Type A lives sympatrically with type B in the Jura mountai ns and is also found in the British Isles. Sympatry of the two types i n the Jura shows that these are separate species. It remains open whet her type B is morphologically atypical F. aquilonia or whether it is a separate species, perhaps with a past history of introgression betwee n F. aquilonia and F. lugubris. The gene frequencies in the Finnish po pulations of F. lugubris differ from those of both types A and B. Gene tic differences within F. lugubris indicate that the populations have evolved separately for a long time. The social structure of F. lugubri s colonies also shows geographic variation. The nests in Finland and t he British Isles seem to be mainly monogynous and monodomous, whereas the nests in Central Europe are polygynous and form polydomous colonie s. F. aquilonia has polygynous and polydomous colonies in all populati ons studied.