Quantitative Biogeography of the Bark Beetles (Coleoptera, Scolytidae) in Northern Europe

Helsinki

1991

35 S.

27 Abb., 5 Tab., zahlr. Lit. Ang.

Bandaufführung

2623

36999

Biogeographical patterns of the Scolytidae in Fennoscandia and Denmark, based on species incidence data from the approximately 70 km x 70 km quadrats (n = 221) used by Lekander et al (1977), were classified and related to environmental variables using multivariate methods (two-way indicator species analysis, detrended correspondence analysis, canonical correspondence analysis). The distributional patterns of scolytid species composition showed similar features to earlier presented zonations based on vegetation composition. One major difference, however, was that the region was more clearly dividied in an east-west direction. Temperature variables associated with the location of the quadrat had the highest canonical coefficient calues on the forst axi of the CCA. Although these variables were the most important determinants of the biogeographical variation in the beetle species assemblages, annual precipitation and the distribution of Picea abies also improved the fit of the species data. Samples with the most deviant rarity and typicalness indices for the scolytid species assemblages in each quadrat were concentrated in several southern Scandinavian quadrats, in some quadrats in northern Sweden, and especially on the Swedish islands (Oeland, Gotland, Gotska Sandoen) in the Baltic Sea. The use of rarity indices which do not take the number of species per quadrat into account, also resulted in high values for areas near Stockholm and Helsinki with wll- known faunas. Methodological tests in which the real changes in the distribution of Ips acuminatus and I. amitinus were used as indicators showed that the currently available multivariate methods are sensitive to small faunal shifts even, and thus permit analysis of the fauna in relation to environmental changes. However, this requires more detailed monitoring of the species' distributions over longer time spans. Distributions of seven species (Scolytus intricatus, S. laevis, Hylurgops glabratus, Crypturgus cinereus, Pityogenes saalasi, Ips typographus and Xyleborus dispar) were predicted by logistic regression models using climatic variables. In spite of the deficiencies in the data and the environmental variables selected, the models were relatively good for several but not for all species. The potential effects of climate change on bark beetles are discussed.