Resource partitioning of four sympatric bark beetles depending on swarming dates and tree species

The niche relationships among bark beetle species attacking pines in northern Spain were studied at three localities with respect to tree species (Pinus radiata and P. sylvestris) and swarming time. Four bark beetle species were found attacking the trees, but not all four species were present at all sites: Tomicus piniperda, Ips sexdentatus, Orthotomicus erosus and Pityogenes bidentatus. Niche width and overlap were affected by resource availability, arrival sequence and attack density. In general, I: piniperda showed the widest niche breadth and was the first swarming species. The largest niche overlaps were found at the sites where the resource was less limiting. The niche overlap between T piniperda and O, erosus depended mainly on the swarming time. The portion of the niche of O. erosus occupied by I: piniperda was greater than that of I: piniperda occupied by O. erosus at the site in which I: piniperda swarmed first. In general, the bark species appeared segregated from each other, bark thickness being a good segregating factor. (C) 1998 Elsevier Science B.V.