Alien Scolytines on the Osa Peninsula, Costa Rica (Coleoptera: Curculionidae: Scolytinae)

Abstract

Alien (exotic) insects threaten trees, landscapes, and ecosystem stability. Bark and ambrosia beetles (Coleoptera: Curculionidae: Scolytinae) are saproxylic beetles that spend most of their life cycles under bark, and often are introduced to new locations through wooden packing materials used in international trade. This project reports the identification of 4 alien species reared on the Osa Peninsula of Costa Rica. Bait branches from 41 trees were exposed to saproxylic beetles in a mosaic of old growth and secondary forest. The branches yielded 6,578 scolytines in 33 species. Four of these were alien species: Coccotrypes cyperi Beeson, Premnobius cavipennis Eichhoff, Xylosandrus crassiusculus Motschulsky, and Xylosandrus morigerus Blandford (all Coleoptera: Curculionidae). At least 1 of the alien species, Premnobius cavipennis, was the most abundant scolytine, represented by 1,476 individuals, and it emerged from almost half of the trees sampled. It was reared from the plant families Lecythidaceae, Sapotaceae, and Fabaceae. Most individuals emerged from bait branches in old growth forest, and were disproportionately abundant at canopy stratum. Only 46 individuals of the economic pest X. crassiusculus were reared from bait branches. Two of the 4 alien scolytines were reared commonly from branches in old growth forest, even though mature forest typically resists invasions of alien species. Unfertilized females can disperse and found colonies by mating with haploid sons, and intra-colony mating promotes rapid population growth; therefore, these life history traits facilitate invasion.