Curculionid beetles associated with willow ( Salix spp.) were surveyed at 42 sites across Europe, from Greece (lat. 38.8 °N) to arctic Norway (lat. 69.7 °N). DNA sequence data provide additional verification of identifications and geographic clustering.
In all, 73 curculionid species were collected from willows, of which seven were particularly abundant. The most widespread species were: Acalyptus carpini Fabricius, 1793 at 15 sites; Tachyerges stigma Germar, 1821 at 13 sites; Phyllobius oblongus (Linnaeus, 1758) at 11 sites; Phyllobius maculicornis Germar, 1824 at 10 sites; and Archarius salicivorus (Paykull, 1792), Melanapion minimum (Herbst, 1797), and Phyllobius cf. pyri (Linnaeus, 1758) all at nine sites. The mean number of curculionid species collected on willow at each site was 5.5 (range 0-14). Compared to chrysomelids, curculionids were richer in species but the species had relatively low average abundance. Widespread curculionid species appear to have scattered and patchy observed distributions with limited geographical structuring in our data. However, deeper sampling (e.g. over multiple seasons and years), would give a better indication of distribution, and may increase apparent geographical structuring. There is some site-to-site variation in colour in a few taxa, but little notable size variation. DNA barcoding, performed on some of the more common species, provides clear species clusters and definitive separation of the taxonomically more challenging species, as well as some interesting geographic insights. Our northernmost sample of Phyllobius oblongus is unique in clustering with Canadian samples of this species. On the other hand, our samples of Acalyptus carpini cluster with European samples and are distinct from a separate Canadian cluster of this species. We provide the first available DNA sequences for Phyllobius thalassinus Gyllenhal, 1834 (Hungary).