Genetic identification of Formica rufa group species and their putative hybrids in northern Europe

Wood ants of the Formica rufa group in northern Europe were studied by using allozyme variation with emphasis on species differences and hybridization. A total of 40 populations and 14,403 workers from 1394 nests were analyzed. Resolution of allozymes was not good enough for classifying individuals or even nest samples into species but proved useful for clustering populations and indicating potential areas of hybridization. Earlier morphological studies have shown that it is difficult to separate northern Formica aquilonia and Formica polyctena from each other. The present genetic results indicate that nearly all F. polyctena in Finland are admixed and their distribution is restricted to the southern parts of the country where hybrids of the two species have been found in earlier studies. In the northernmost populations close to and north of the arctic circle, the results also indicate hybridization between F. aquilonia and Formica lugubris. The results provide background information for studies assessing patterns of genome-wide selection in hybridizing Formica ants and
understanding the effects of climate change on the geographical distribution and hybridization of species.