Sub‐lethal effects of monoterpenes on reproduction by mountain pine beetles

Abstract

1 Plant defences may negatively affect the oviposition behaviour of insect herbivores. We exposed adult female mountain pine beetles Dendroctonus ponderosae (Hopkins) to monoterpene vapours and assessed their subsequent oviposition in lodgepole pine Pinus contorta. 2 Exposure to 31.25 and 125 p.p.m. of α-pinene and limonene for 24 h did not affect the survival or establishment of oviposition galleries compared with controls. Females had fewer, smaller eggs and therefore lower cumulative reproduction after exposure to 125 p.p.m. compared with the other treatments. Limonene negatively affected oviposition more than did α-pinene. 3 Female body condition, a measure of energetic state, influenced the responses (i.e. significant interactions between condition and monoterpene concentration). With exposure to 31.25 p.p.m., females in better condition tended to have fewer, larger eggs, whereas females in poorer condition tended to have more, smaller eggs, compared with controls. Overall, reproductive investment declined with body condition when exposed to monoterpenes. Egg size and number increased with female body size. 4 The findings of the present study may indicate the toxic effects of monoterpenes or may be a result of females choosing not to invest in adverse environments depending on body condition. In either case, reduced reproduction when exposed to high plant defences may be increasingly important as climate change affects plant defences.

Tree response and mountain pine beetle attack preference, reproduction and emergence timing in mixed whitebark and lodgepole pine stands

“…Attacked whitebark pine also had a more than seven‐fold greater proportion of limonene than attacked lodgepole pine. Limonene is highly toxic to bark beetles (Werner, 1995; Raffa et al ., ) and can negatively influence MPB reproduction (Manning & Reid, ). Norway spruce that survived Ips typographus L. attacks also had higher limonene concentrations than those that were killed (Schiebe et al ., ).…”

Defence syndromes in lodgepole – whitebark pine ecosystems relate to degree of historical exposure to mountain pine beetles

“…The chemical ecology of host– D. ponderosae – G. clavigera interactions has been studied in some detail, particularly for monoterpenes. Toxicity to beetles is influenced more by concentration than identity (Reid & Purcell ; Manning & Reid ; Reid et al ), a pattern that occurs with other bark beetles such as Ips pini (Say) (Raffa & Smalley ). Limonene may be somewhat more toxic than other monoterpenes, but differences appear relatively minor and inconsistent.…”

Morphological variation associated with dispersal capacity in a tree‐killing bark beetleDendroctonus ponderosaeHopkins

“…In many insects, traits such as wing morphology, flight muscle and body condition can influence flight capacity and dispersal potential (Azevedo et al ., ; Hassall, ). Measurements of such flight‐related traits can be used to infer an individual's ability to disperse, and may also be correlated with successful establishment after dispersal (Manning & Reid, ; Evenden et al ., ). Models that predict dispersal capacity by pest species have become important tools for environmental conservation and resource management through the refinement of damage prevention, especially in cases of range expansion and invasion of novel habitats (Safranyik & Carroll, ).…”

“…Females initiate the attack once they arrive on a host and release aggregation pheromones to attract conspecifics (Blomquist et al ., ) and the bark beetle body condition determines the quality and quantity of their offspring (Kautz et al ., ). Correlations among lipid content, attack success and reproduction in bark beetles have been well documented (Elkin & Reid, ; Reid & Purcell, ; Manning & Reid, ; Kautz et al ., ); larger, heavier beetles have greater lipid content (Evenden et al ., ), resulting in increased fecundity (Elkin & Reid, ) and a greater ability to resist host defences (Reid & Purcell, ). Larger females therefore are potentially better pioneers through their capacity to facilitate range expansion.…”