A pheromone-based toolbox of longhorn beetles (Cerambycidae) for monitoring biodiversity in ephemeral deadwood substrates of oak

Sammanfattning: Forest biodiversity is exhibiting a worldwide decline in response to environmentalchanges that result in the rapid loss, degradation, and fragmentation of essential foresthabitats. Saproxylic insects, especially beetles, are an important part of forestbiodiversity by contributing to deadwood decomposition, and serving as importantcomponents of food webs. Many saproxylic beetles display negative population trends,and are listed on national and European Red Lists of threatened species. Despite theirgreat importance, present knowledge on the ecology and conservation requirements ofthese beetles is limited, in part due to the absence of efficient tools to samplepopulations of many species. Recently, pheromone-based methods have been proposedas a novel tool to study saproxylic insects. Unfortunately, thus far, pheromones haveonly been identified for a small number of species of interest to conservation.In this work I identified the aggregation-sex pheromones of longhorn beetlesdependent on fresh, recently dead, wood substrates of oak in Sweden, and examined theusefulness of the pheromone-based trapping approach for detecting local populations,and studying the species’ ecology. The pheromone-chemistry of eight species wasconsidered, with a total of seven identified pheromone compounds (hydroxyketones,alcohols, and one ketone). The pheromones were used for systematic, large-scalemonitoring studies in southern Sweden. The results served to significantly change theperception of several species’ distribution and abundance. Further, local beetleabundance (trap captures), was best correlated with habitat at relatively large spatialscales, indicating that future detailed analyses of the species’ ecology need to considerlarge spatial scales. Effects of oak forest management and habitat structure wereexamined in a three-year monitoring study. Generally, beetle abundance did not differbetween ordinary oak production stands and two types of set-aside habitats forbiodiversity. Most species also preferred more open, sun-exposed oak habitats. Inaddition, the beetles displayed short-term positive responses to logging in oakproduction stands, when fresh oak substrates were retained on site. The work clearlydemonstrated the advantages of using pheromones to study these species and alsooffered early insights into the complicated, and highly dynamic, ecology of the species.