The biologies of two hemlock barkbeetles in western Oregon

The objectives undertaken in this study were to investigate the biologies and potential economic importance of Pseudohylesinus tsugae Swaine and P. grandis Swaine in young coastal stands of western hemlock (Tsuga heterophylla (Rafn.) Sarg.). The life and seasonal histories of P. tsugae and P. grandis and the association of these two scolytids with the hemlock bark maggot (Cheilosia alaskensis Hunter) are presented. Both P. tsugae and P. grandis were found to have one generation a year with two broods. Both species had four larval instars. P. grandis overwintered either as a fourth instar larva or as a teneral adult. P. tsugae usually overwintered as a fourth instar larva. Within thinned stands of western hemlock P. tsugae preferred fresh stumps for breeding material, whereas P. grandis preferred fresh slash. The teneral adults of both P. tsugae and P. grandis fed in the inner-bark region of standing live host trees before initiating egg galleries in suitable breeding material. Within the thinned stands these feeding sites provided entry to the cambial region of the tree for the hemlock bark maggot. Both the number of maggot infestations and Pseudohylesinus spp. feeding sites within a stand increased after the stand was thinned. A potential method of control of both P. tsugae and P. grandis and the hemlock bark maggot was found

The evolution of mating systems in bark and ambrosia beetles (Coleoptera: Scolytidae and Platypodidae)

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72492/1/j.1096-3642.1983.tb00858.x.pd

Monoterpene Variation Mediated Attack Preference Evolution of the Bark Beetle Dendroctonus valens

Several studies suggest that some bark beetle like to attack large trees. The invasive red turpentine beetle (RTB), Dendroctonus valens LeConte, one of the most destructive forest pests in China, is known to exhibit this behavior. Our previous study demonstrated that RTBs preferred to attack large-diameter trees (diameter at breast height, DBH ≥30 cm) over small-diameter trees (DBH ≤10 cm) in the field. In the current study, we studied the attacking behavior and the underlying mechanisms in the laboratory. Behavioral assays showed that RTBs preferred the bark of large-DBH trees and had a higher attack rate on the bolts of these trees. Y-tube assays showed that RTBs preferred the volatiles released by large-DBH trees to those released by small-DBH trees. Subsequent analysis revealed that both large- and small-DBH trees had the same composition of monoterpenes, but the concentration of each component differed; thus it appeared that the concentrations acted as cues for RTBs to locate the right-sized host which was confirmed by further behavioral assays. Moreover, large-DBH pine trees provided more spacious habitat and contained more nutrients, such as nitrogen, than did small-DBH pine trees, which benefited RTBs' fecundity and larval development. RTBs seem to have evolved mechanisms to locate those large hosts that will allow them to maximize their fitness. Monoterpene variation mediated attack preference implies the potential for the management of RTB

Data from: Repurposing population genetics data to discern genomic architecture: a case study of linkage cohort detection in mountain pine beetle (Dendroctonus ponderosae)

Genetic surveys of the population structure of species can be used as resources for exploring their genomic architecture. By adjusting filtering assumptions, genome-wide single nucleotide polymorphism (SNP) datasets can be reused to give new insights into the genetic basis of divergence and speciation without targeted re-sampling of specimens. Filtering only for missing data and minor allele frequency, we used a combination of principle components analysis and linkage disequilibrium network analysis to distinguish three cohorts of variable SNPs in the mountain pine beetle in western Canada, including one that was sex-linked and one that was geographically associated. These marker cohorts indicate genomically localized differentiation, and their detection demonstrates an accessible and intuitive method for discovering potential islands of genomic divergence without a priori knowledge of a species’ genomic architecture. Thus, this method has utility for directly addressing the genomic architecture of species and generating new hypotheses for functional research