Evaluating Seasonal Variation in Bottom-Up and Top-Down Forces and Their Impact on an Exotic Wood Borer,Tetropium fuscum(Coleoptera: Cerambycidae)

Abstract

It is well understood that forces from multiple trophic levels simultaneously influence herbivore performance, but how the relative strength of these forces vary over space and time is less clear. We evaluated seasonal variation in the impact of bottom-up forces (host condition), top-down forces (natural enemies), and competition on the performance of an exotic wood borer. Tetropium fuscum (F.) (Coleoptera: Cerambycidae) eggs that were either protected or exposed were placed on healthy and stressed red spruce, Picea rubens Sargent, trees at three different times during the natural T. fuscum flight period. We also measured the length of necrotic lesions (i.e., an induced hypersensitive response) that developed in response to attacking T. fuscum. As predicted, T. fuscum performance was usually greater, and induced host defenses lower, on stressed than on healthy trees, but the impact of host condition on T. fuscum performance varied seasonally. Timing of attack was critical, influencing the strength of bottom-up forces and consequently all measures of T. fuscum performance. Survival was reduced when T. fuscum attacked too early (late-May) or too late (late-June), which may result in stabilizing selection for attack time in this species. Parasitism and competition were generally negligible during this study. Our results suggest that timing of attack is critical for this wood borer and that temporal variation in the impact of top-down and bottom-up forces should be considered in other systems.

Do visual cues associated with larger diameter trees influence host selection by Tetropium fuscum (Coleoptera: Cerambycidae)?

“…As larval development rate and survival of T. fuscum were also greater in girdled trees than in healthy trees (Flaherty et al . 2011, 2013a) the preference for girdled trees supported the preference–performance hypothesis (Jaenike 1978; Flaherty et al . 2013b).…”

“…Flaherty et al (2013b) showed that adult T. fuscum preferred to land on and lay more eggs on red spruce trees (Picea rubens Sargent) that had been moisture stressed by girdling compared with unmanipulated trees, and further showed that the beetles were more discriminating before they landed on the host than afterward. As larval development rate and survival of T. fuscum were also greater in girdled trees than in healthy trees (Flaherty et al 2011(Flaherty et al , 2013a) the preference for girdled trees supported the preference-performance hypothesis (Jaenike 1978;Flaherty et al 2013b).…”

“…In both Europe and Nova Scotia, it primarily infests spruce, Picea Dietrich (Pinaceae) species, that are stressed, weakened, or of low vigour (Juutinen 1955; Flaherty et al . 2013a). Flaherty et al .…”

“…The brown spruce longhorn beetle, Tetropium fuscum (Fabricius) (Coleoptera: Cerambycidae), is an invasive insect native to Europe that has been established in Nova Scotia, Canada since at least 1990 (Smith and Hurley 2000). In both Europe and Nova Scotia, it primarily infests spruce, Picea Dietrich (Pinaceae) species, that are stressed, weakened, or of low vigour (Juutinen 1955;Flaherty et al 2013a). Flaherty et al (2013b) showed that adult T. fuscum preferred to land on and lay more eggs on red spruce trees (Picea rubens Sargent) that had been moisture stressed by girdling compared with unmanipulated trees, and further showed that the beetles were more discriminating before they landed on the host than afterward.…”

Seasonal Prevalence of the Invasive Longhorn Beetle Aromia bungii in Osaka Prefecture, Japan

“…This regional difference has also been reported in other cerambycids in Japan [ 10 , 11 ]. Moreover, seasonal prevalence in a region has been reported to vary annually [ 12 , 13 ]. Considering this expected variation, a multi-year and multi-site survey in a region can help to identify a general trend of seasonal prevalence in the region; however, such surveys have rarely been conducted for A. bungii adults.…”