Mating Systems of the Tree-Killing Bark Beetle Polygraphus proximus (Coleoptera: Curculionidae: Scolytinae)

Abstract

Polygraphus proximus Blandford (Coleoptera: Curculionidae: Scolytinae) has caused mass mortality of fir (Abies spp. (Pinaceae)) forests across large areas of Russia in the past decade. More recently, mass mortality of A. veitchii Lindl. due to P. proximus infestation has been reported in Japan. This bark beetle species traditionally has been considered to be polygynous because their galleries have multiple gallery arms, and because harem-polygyny is common in the tribe Polygraphini. Although the mating system(s) potentially could have a marked effect on their reproductive success and population dynamics, the reproductive behavior of the tree-killing bark beetle P. proximus has not been investigated in detail in a natural setting in Japan. We, therefore, investigated the number of males and females in a gallery and the number of gallery arms in Abies species in Japan. None of the galleries examined contained more than one male, and 57.2% of the galleries had multiple gallery arms, even though only 2.8% of the galleries contained two females. The findings showed that the typical mating system employed by P. proximus is monogyny and that this species constructs multiple gallery arms in each gallery. In addition, 70.4% of galleries in which the sex of adult beetles could be determined contained no males, and 26.6% contained no females, suggesting that P. proximus males and females re-emerge.

Host preference of the tree‐killing bark beetle Polygraphus proximus across a geographic boundary separating host species

“…Whereas it is expected that sex and/aggregation pheromones exist, these were never confirmed (Kabe, 1959;Nobuchi, 1980). The mating system of P. proximus is monogyny (Kerchev, 2014a;Köbayashi & Takagi, 2020), and the females produce double-armed horizontal mother-galleries beneath the bark in which they lay their eggs (Kabe, 1959;Nobuchi, 1966;Kerchev, 2014a;Köbayashi et al 2022). Each adult offspring makes its own exit hole (Kabe, 1959;Nobuchi, 1980).…”

Identification of sex-specific compounds in the invasive four-eyed fir bark beetle Polygraphus proximus

“…Other studies have indicated that the males produce a pheromone which attracts females (Kerchev 2014b) or that both males and females of P. proximus can secrete aggregation pheromones (Krivets et al 2019). P. proximus is a monogamous species, unlike most other species in the Polygraphus genus (Kerchev 2014b;Köbayashi and Takagi 2020). In four other Polygraphus species, male-specific aggregation pheromones have been found.…”

Colonization success of a tree‐killing bark beetle: Geographic variation and mismatch with host preference

“…The mating system of P . proximus is monogynous (Kerchev, 2014a ; Köbayashi & Takagi, 2020 ). Although a male sex pheromone is suspected to play a role in mating, this role has not been confirmed yet (Kabe, 1959 ; Nobuchi, 1980 ).…”

“…The emergence period and subsequent flight of the first generation of adults occur at the end of spring or at the beginning of summer (May-July), and the second generation emerges from the infested trees at the end of summer (August-September;EFSA, 2020;EPPO, 2014). The mating system of P. proximus is monogynous (Kerchev, 2014a;Köbayashi & Takagi, 2020). Although a male sex pheromone is suspected to play a role in mating, this role has not been confirmed yet (Kabe, 1959;Nobuchi, 1980).…”