Individual variation in bark beetle and moth pheromones ‐ a comparison and an evolutionary background

Abstract

The presently published data of variation in pheromone content in bark beetles (Coleoptera: Scolytidae) and moths (Lepidoptera) are reviewed. In both taxa high coefficients of variation, often up to around 100% for amount of pheromone, seem to be the rule. The contribution to the variation from errors in the chemical methods was small in most studies compared with the intrinsic biological variation. Examples arc given of variation in both absolute amounts, proportions of geometric isomers and in enantiomeric composition. Ratios of isomers often had lower coefficients of variation (25% or less). A lower average variation among sex pheromone in moths could relate to a mating system involving singly calling females, compared with the aggregation pheromone of bark beetles, which often call in large groups. The origin of a resource‐based aggregation pheromone system by evolution working via individual selection is outlined.

High individual variation in pheromone production by tree-killing bark beetles (Coleoptera: Curculionidae: Scolytinae)

“…; Steed and Wagner 2004). Schlyter and Birgersson (1989) provide evidence that solitary callers like moths vary less meanCV AE SD ¼ ð 69% AE 20;n ¼ 15Þ compared to bark beetle systems meanCV AE SD ¼ 119% AE 32;n ¼ 9 ð Þ . Figure 3 suggests quantitative, falsifiable predictions for how the variance in pheromone production should decrease as typical aggregation sizes become smaller.…”

Mixed messages across multiple trophic levels: the ecology of bark beetle chemical communication systems

“…Flexible strategies have been proposed for host selection behavior (Raffa & Berryman 1983a, and could likewise apply to pheromonal responses (e.g., see Schlyter & Birgersson 1989). Recent advances in the areas of scolytid genetics and within-and among-population variation (e.g., Miller et al 1989b;Berisford et al 1990;Hager & Teale 1996;Seybold et al 1992Seybold et al , 1995bSeybold 1993) lend support to this possibility, and delineate some key areas for further research.…”

“…Such questions of scaling up and scaling down across multiple levels of biological organization comprise one of the seminal issues currently facing all ecologists. Complexity arises at many scales -the multiple ecological functions in which bark beetle pheromones exert feedback, their variation in space and time, the heritable and environmentally induced plasticity among individuals, and the difficulty of communicating under natural conditions (Schlyter & Birgersson 1989;Berisford et al 1990;Miller et al 1997). Beetles are confronted with plant species compositions in their forest habitats that can range from highly diverse communities to almost pure monocultures (both natural and managed).…”

Dynamics of pheromone production and communication in the mountain pine beetle, Dendroctonus ponderosae Hopkins, and the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae)

“…This observation is consistent with a range of 0-2638 ng of ipsdienol found in male I. pini fed on lodgepole pine ( Borden et al 1986). The aggregative behaviour of bark beetles may enable weak pheromone producers to acquire mates andrcproduce (Schlyter and Birgersson 1989). The antennae of 1. pini had low perception thresholds (0.01 W ) and very high saturation levels to ipsdienol compared to thresholds of 0.1 pg and 0.5 pg to the antiaggregants verbenone and trans-verbenol respectively, allowing for long distance detection and orientation towards low emissions of ipsdienol (Angst and Lanier 1979).…”