Maintenance of endemic Dendroctonus ponderosae populations through interactions with a secondary bark beetle, Pseudips mexicanus.

Endemic Dendroctonus ponderosae are often found inhabiting weakened lodgepole pine (Pinus contorta var. latifolia) in western Canada previously attacked by the little known bark beetle Pseudips mexicanus. Interactions between the two species have not been elucidated, so three studies were conducted. The first examined the life history of P. mexicanus, describing developmental characteristics. The second explored the interaction between the two species and found the D. ponderosae attacking ephemeral hosts previously occupied by P. mexicanus do so in greater densities with earlier offspring emergence when compared to hosts D. ponderosae attacked alone. P. mexicanus may alter host chemistry, allowing D. ponderosae to be more successful when compared to trees D. ponderosae attacked alone. The third study investigated the attraction of D. ponderosae to P. mexicanus-produced volatiles, revealing no response by D. ponderosae. The scope of this work contributes to the understanding of bark beetle ecology in the lodgepole pine ecosystem.--P.ii