Interactions among sympatric bark beetle species mediated by resource availability

Three species of Ips infest pine in the Great Lakes Region (I. grandicollis, I. pini, I. perroti). I addressed the effect of resource availability on Ips populations and the interactions that occur among these species in exploiting a shared resource--red pine phloem. Research was conducted in red pine monocultures in Dunn County, Wisconsin (west-central). I. grandicollis possess superior powers of host location and use a broader range of resources than I. pini and I. perroti. These differences result in characteristic patterns of infestation within host trees. Due to variation among the species in voltinism and possibly dispersal, resource availability as determined by commercial timber harvests has the greatest effect on I. pini populations and the least effect on I. grandicollis populations. Summer I. pini population densities may be reduced through spring resource competition with I. grandicollis and I. perroti, thereby decreasing risk of tree mortality.