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Predicting range expansion of an ectoparasite – the effect of spring and summer temperatures on deer ked Lipoptena cervi (Diptera: Hippoboscidae) performance along a latitudinal gradient


  • Laura Härkönen,

  • Sauli Härkönen,

  • Arja Kaitala,

  • Sirpa Kaunisto,

  • Raine Kortet,

  • Sauli Laaksonen,

  • Hannu Ylönen

L. Härkönen ( and A. Kaitala, Univ. of Oulu, Dept of Biology, P.O. Box 3000, FI-90014 Oulu, Finland. – S. Härkönen, Finnish Forest Research Inst., Joensuu Research Unit, P.O. Box 68, FI-80101 Joensuu, Finland. – S. Kaunisto and R. Kortet, Univ. of Eastern Finland, Dept of Biology, P.O. Box 111, FI-80101 Joensuu, Finland. – S. Laaksonen, Finnish Food Safety Authority, Fish and Wildlife Health Research Unit, P.O. Box 517, FI-90101 Oulu, Finland. – H. Ylönen, Univ. of Jyväskylä, Dept Biological and Environmental Science, Konnevesi Research Station, P.O. Box 35, FI-40014 Jyväskylä, Finland.


The range expansion of organisms towards higher latitudes and altitudes is often limited by colder temperatures and the shorter growth season. In parasites, survival outside the host is most likely to affect their potential establishment in novel environments. We conducted a large scale transplant experiment to predict the potential spread of the deer ked Lipoptena cervi (Diptera: Hippoboscidae), a blood-feeding ectoparasite of boreal cervids. We studied the off-host survival and pupal development of deer ked in five sites along a latitudinal gradient reaching from its current range in central Finland to northernmost Fennoscandia. We showed that the deer ked is able to survive and complete its development even in arctic environments, 500 km northwards beyond the current range. Performance deteriorated steadily towards north, where lower summer temperatures prolonged the developmental period and shortened the suitable host search time by several weeks. The relevance of the experiments for estimating the spread of deer ked to the north is discussed.