From arrival to spread: improving the early-detection of alien wood-boring beetles

The introduction of alien species in new habitats is a global and growing problem worldwide. Since the discovery of the Americas about 10,000 species have been introduced in Europe, mainly plants and insects. Among the latter, wood-boring beetles (mainly Scolytinae, Cerambycidae and Buprestidae) are recognized as one of the most successful group of invaders. These insects can be transported in almost all types of woody materials and, once introduced and established, they can cause enormous damage to ecosystems and economies of the invaded countries. In addition to traditional control methods, in the last years several countries have implemented other kinds of tools, such as traps baited with attractive lures, in order to enhance the chances of alien wood-boring beetles interception. Resources available for these activities are however limited while the number of sites that should be monitored is extremely high. For this reason, it is of utmost importance to have reliable and efficient trapping protocols as well as to understand where surveillance efforts should be focused. However, the general solution of this problem is strictly related to a better comprehension of the three steps characterizing the invasion process: arrival, establishment and spread. This thesis has two main aims: first, to enhance the early-detection of alien wood-boring beetles at high-risk sites located both in coastal and continental areas, and second, to gain insight into the mechanisms driving the alien wood-boring beetle invasion process. The first study concerns the development of efficient early-detection protocols that can be adopted for the interception of alien wood-boring beetles arriving at European ports of entry. This is focused on how different use of attractive lures, different trap models and trap positions (inside ports vs surrounding areas) may influence the chances of interception of alien species. The results suggest the use of multi-funnel traps baited with different lures for monitoring alien wood-boring beetles. The deployment of traps outside the port is also recommended to validate the surveillance program. The second study concerns how port size, in terms of amount of imported commodities, and characteristics of the landscape surrounding the ports, in terms of forest cover and forest composition, may affect the early-detection of alien wood-boring beetles. The results suggest that surveillance should be focused mainly in large ports and in the surrounding broadleaf forests, deploying traps simultaneously in both habitats. The third study is focused on the comparison between ports of entry and wood waste landfills, considered as the final destination of a large part of wood packaging materials imported together with goods. The results show that wood waste landfills are a crucial site where detecting alien species associated with woody materials, even in continental areas far away from the coasts. The forth and fifth studies investigate how the main climatic and environmental variables affect the establishment and spread of alien bark and ambrosia beetles at both regional and continental scale. The main results demonstrate that the invasion process of exotic scolytids is not random and that both climate and forest composition play a key role in shaping their communities and their spatial distribution in the invaded environment. However, these mechanisms occur differently according to the feeding guild of the two main groups of scolytids, the bark beetles and the ambrosia beetles. In general, the five studies carried out in this thesis provide suggestions to increase the probability of an early-detection of alien species both in coastal and continental areas, describing a protocol applicable both at local and international scale. At the same time, they contribute to improve the knowledge about the mechanisms characterizing the invasion process of alien wood-boring beetles, information that can be of utmost importance for the development of future strategies focused to reduce economic and environmental damage due to alien species

Acquisition of fungi from the environment modifies ambrosia beetle mycobiome during invasion

Microbial symbionts can play critical roles when their host attempts to colonize a new habitat. The lack of symbiont adaptation can in fact hinder the invasion process of their host. This scenario could change if the exotic species are able to acquire microorganisms from the invaded environment. Understanding the ecological factors that influence the take-up of new microorganisms is thus essential to clarify the mechanisms behind biological invasions. In this study, we tested whether different forest habitats influence the structure of the fungal communities associated with ambrosia beetles. We collected individuals of the most widespread exotic (Xylosandrus germanus) and native (Xyleborinus saxesenii) ambrosia beetle species in Europe in several old-growth and restored forests. We characterized the fungal communities associated with both species via metabarcoding. We showed that forest habitat shaped the community of fungi associated with both species, but the effect was stronger for the exotic X. germanus. Our results support the hypothesis that the direct contact with the mycobiome of the invaded environment might lead an exotic species to acquire native fungi. This process is likely favored by the occurrence of a bottleneck effect at the mycobiome level and/or the disruption of the mechanisms sustaining co-evolved insect-fungi symbiosis. Our study contributes to the understanding of the factors affecting insect-microbes interactions, helping to clarify the mechanisms behind biological invasions

Investigating beetle communities in and around entry points can improve surveillance at national and international scale

Beetles are commonly moved among continents with international trade. Baited traps set up in and around entry points are commonly used to increase chances of early-detection of incoming species and complement visual inspections. A still underestimated benefit of this surveillance approach is the high number and diversity of collected bycatch species. In this study, we exploited a multiyear surveillance program carried out with baited traps at five Spanish ports and their surrounding natural areas to investigate i) the importance of identifying bycatch to more promptly detect nonnative species belonging to non-target groups; ii) patterns of native and nonnative species richness and abundance inside the port areas vs. surrounding natural areas; iii) the occurrence of spillover events between natural areas surrounding ports and the port areas, and iv) whether the native species most commonly introduced into other countries are more abundant in port areas than in surrounding natural areas. A total of 23,538 individuals from 206 species representing 33 families were collected. The number and taxonomic diversity of the 26 bycatch nonnative beetle species testified that the identification of these unintentionally trapped species can provide additional information on ongoing invasions. Patterns of spillover and native species richness and abundance in port areas vs. surrounding natural areas highlighted a differential ability of different beetle families to colonize port areas. Finally, native species most commonly introduced into other countries were more abundant in port areas than in their surroundings, while the opposite trend occurred for native species that have not been introduced elsewhere. Our study highlighted that the use of traps baited with generic attractants can aid in early-detection of nonnative beetle species, and that the identification of native species can provide useful information on the risk of introduction in other countries.The study was funded by the Servei d’Ordenació i Gestió Forestal (Conselleria d’Agricultura, Desenvolupament Rural, Emergència Climàtica i Transició Ecològica) of Generalitat Valenciana. Davide Rassati was partially supported by the CRUI-CARE Agreement. 2019 STARS Grants programme (project: MOPI–Microorganisms as hidden players in insect invasions)

Investigating beetle communities in and around entry points can improve surveillance at national and international scale

Beetles are commonly moved among continents with international trade. Baited traps set up in and around entry points are commonly used to increase chances of early-detection of incoming species and complement visual inspections. A still underestimated benefit of this surveillance approach is the high number and diversity of collected bycatch species. In this study, we exploited a multiyear surveillance pro-gram carried out with baited traps at five Spanish ports and their surrounding natural areas to investigate i) the importance of identifying bycatch to more promptly detect nonnative species belonging to non-target groups; ii) patterns of native and nonnative species richness and abundance inside the port areas vs. surrounding natural areas; iii) the occurrence of spillover events between natural areas surrounding ports and the port areas, and iv) whether the native species most commonly introduced into other countries are more abundant in port areas than in surrounding natural areas. A total of 23,538 individuals from 206 species representing 33 families were collected. The number and taxonomic diversity of the 26 bycatch nonnative beetle species testified that the identification of these unintentionally trapped species can pro-vide additional information on ongoing invasions. Patterns of spillover and native species richness and abundance in port areas vs. surrounding natural areas highlighted a differential ability of different beetle families to colonize port areas. Finally, native species most commonly introduced into other countries were more abundant in port areas than in their surroundings, while the opposite trend occurred for native species that have not been introduced elsewhere. Our study highlighted that the use of traps baited with generic attractants can aid in early-detection of nonnative beetle species, and that the identification of native species can provide useful information on the risk of introduction in other countrie

Common pathways by which non-native forest insects move internationally and domestically

International trade and movement of people are largely responsible for increasing numbers of non-native insect introductions to new environments. For forest insects, trade in live plants and transport of wood packaging material (WPM) are considered the most important pathways facilitating long-distance invasions. These two pathways as well as trade in firewood, logs, and processed wood are commonly associated with insect infestations, while “hitchhiking” insects can be moved on cargo, in the conveyances used for transport (e.g., containers, ships), or associated with international movement of passengers and mail. Once established in a new country, insects can spread domestically through all of the above pathways. Considerable national and international efforts have been made in recent years to reduce the risk of international movement of plant pests. International Standards for Phytosanitary Measures (ISPMs) No. 15 (WPM), 36 (plants for planting), and 39 (wood) are examples of phytosanitary standards that have been adopted by the International Plant Protection Convention to reduce risks of invasions of forest pests. The implementation of ISPMs by exporting countries is expected to reduce the arrival rate and establishments of new forest pests. However, many challenges remain to reduce pest transportation through international trade, given the ever-increasing volume of traded goods, variations in quarantine procedures between countries, and rapid changes in distribution networks. It is therefore likely that many more human-assisted invasions of forest insects will take place. New geographic expansions by natural modes are also made possible due to changes in host distribution and/or climate.http://link.springer.com/journal/103402020-01-01hj2018Forestry and Agricultural Biotechnology Institute (FABI)Zoology and Entomolog

Special issue on invasive pests of forests and urban trees : pathways, early detection, and management

This special issue on pathways, early detection, and management of invasive pests of forests and urban trees was spawned in a symposium entitled “Invasive species surveillance: new methods and tools for survey and early detection,” held at the International Union of Forestry Research Organizations (IUFRO) 125th Anniversary Congress in Freiburg, Germany, September 19–22, 2017.http://link.springer.com/journal/103402020-01-04hj2019Forestry and Agricultural Biotechnology Institute (FABI)Zoology and Entomolog

Recent advances toward the sustainable management of invasive Xylosandrus ambrosia beetles

We provide an overview of both traditional and innovative control tools for management of three Xylosandrus ambrosia beetles (Coleoptera: Curculionidae: Scolytinae), invasive species with a history of damage in forests, nurseries, orchards and urban areas. Xylosandrus compactus, X. crassiusculus and X. germanus are native to Asia, and currently established in several countries around the globe. Adult females bore galleries into the plant xylem inoculating mutualistic ambrosia fungi that serve as food source for the developing progeny. Tunneling activity results in chewed wood extrusion from entry holes, sap outflow, foliage wilting followed by canopy dieback, and branch and trunk necrosis. Maintaining plant health by reducing physiological stress is the first recommendation for long-term control. Baited traps, ethanol-treated bolts, trap logs and trap trees of selected species can be used to monitor Xylosandrus species. Conventional pest control methods are mostly ineffective against Xylosandrus beetles because of the pests’ broad host range and rapid spread. Due to challenges with conventional control, more innovative control approaches are being tested, such as the optimization of the push–pull strategy based on specific attractant and repellent combinations, or the use of insecticide-treated netting. Biological control based on the release of entomopathogenic and mycoparasitic fungi, as well as the use of antagonistic bacteria, has yielded promising results. However, these technologies still require validation in real field conditions. Overall, we suggest that management efforts should primarily focus on reducing plant stress and potentially be combined with a multi-faceted approach for controlling Xylosandrus damage

Worldwide tests of generic attractants, a promising tool for early detection of non-native cerambycid species

A large proportion of the insects which have invaded new regions and countries are emerging species, being found for the first time outside their native range. Being able to detect such species upon arrival at ports of entry before they establish in non-native countries is an urgent challenge. The deployment of traps baited with broad-spectrum semiochemical lures at ports-of-entry and other high-risk sites could be one such early detection tool. Rapid progress in the identification of semiochemicals for cerambycid beetles during the last 15 years has revealed that aggregation-sex pheromones and sex pheromones are often conserved at global levels for genera, tribes or subfamilies of the Cerambycidae. This possibly allows the development of generic attractants which attract multiple species simultaneously, especially when such pheromones are combined into blends. Here, we present the results of a worldwide field trial programme conducted during 2018-2021, using traps baited with a standardised 8-pheromone blend, usually com-plemented with plant volatiles. A total of 1308 traps were deployed at 302 sites covering simultaneously or sequentially 13 European countries, 10 Chinese provinces and some regions of the USA, Canada, Australia, Russia (Siberia) and the Caribbean (Martinique). We intended to test the following hypotheses: 1) if a species is regularly trapped in significant numbers by the blend on a continent, it increases the prob-ability that it can be detected when it arrives in other countries/continents and 2) if the blend exerts an effective, generic attraction to multiple species, it is likely that previously unknown and unexpected spe-cies can be captured due to the high degree of conservation of pheromone structures within related taxa. A total of 78,321 longhorned beetles were trapped, representing 376 species from eight subfamilies, with 84 species captured in numbers greater than 50 individuals. Captures comprised 60 tribes, with 10 tribes including more than nine species trapped on different continents. Some invasive species were captured in both the native and invaded continents. This demonstrates the potential of multipheromone lures as ef-fective tools for the detection of 'unexpected' cerambycid invaders, accidentally translocated outside their native ranges. Adding new pheromones with analogous well-conserved motifs is discussed, as well as the limitations of using such blends, especially for some cerambycid taxa which may be more attracted by the trap colour or other characteristics rather than to the chemical blend

From arrival to spread: improving the early-detection of alien wood-boring beetles

The introduction of alien species in new habitats is a global and growing problem worldwide. Since the discovery of the Americas about 10,000 species have been introduced in Europe, mainly plants and insects. Among the latter, wood-boring beetles (mainly Scolytinae, Cerambycidae and Buprestidae) are recognized as one of the most successful group of invaders. These insects can be transported in almost all types of woody materials and, once introduced and established, they can cause enormous damage to ecosystems and economies of the invaded countries. In addition to traditional control methods, in the last years several countries have implemented other kinds of tools, such as traps baited with attractive lures, in order to enhance the chances of alien wood-boring beetles interception. Resources available for these activities are however limited while the number of sites that should be monitored is extremely high. For this reason, it is of utmost importance to have reliable and efficient trapping protocols as well as to understand where surveillance efforts should be focused. However, the general solution of this problem is strictly related to a better comprehension of the three steps characterizing the invasion process: arrival, establishment and spread. This thesis has two main aims: first, to enhance the early-detection of alien wood-boring beetles at high-risk sites located both in coastal and continental areas, and second, to gain insight into the mechanisms driving the alien wood-boring beetle invasion process. The first study concerns the development of efficient early-detection protocols that can be adopted for the interception of alien wood-boring beetles arriving at European ports of entry. This is focused on how different use of attractive lures, different trap models and trap positions (inside ports vs surrounding areas) may influence the chances of interception of alien species. The results suggest the use of multi-funnel traps baited with different lures for monitoring alien wood-boring beetles. The deployment of traps outside the port is also recommended to validate the surveillance program. The second study concerns how port size, in terms of amount of imported commodities, and characteristics of the landscape surrounding the ports, in terms of forest cover and forest composition, may affect the early-detection of alien wood-boring beetles. The results suggest that surveillance should be focused mainly in large ports and in the surrounding broadleaf forests, deploying traps simultaneously in both habitats. The third study is focused on the comparison between ports of entry and wood waste landfills, considered as the final destination of a large part of wood packaging materials imported together with goods. The results show that wood waste landfills are a crucial site where detecting alien species associated with woody materials, even in continental areas far away from the coasts. The forth and fifth studies investigate how the main climatic and environmental variables affect the establishment and spread of alien bark and ambrosia beetles at both regional and continental scale. The main results demonstrate that the invasion process of exotic scolytids is not random and that both climate and forest composition play a key role in shaping their communities and their spatial distribution in the invaded environment. However, these mechanisms occur differently according to the feeding guild of the two main groups of scolytids, the bark beetles and the ambrosia beetles. In general, the five studies carried out in this thesis provide suggestions to increase the probability of an early-detection of alien species both in coastal and continental areas, describing a protocol applicable both at local and international scale. At the same time, they contribute to improve the knowledge about the mechanisms characterizing the invasion process of alien wood-boring beetles, information that can be of utmost importance for the development of future strategies focused to reduce economic and environmental damage due to alien species.L’introduzione di organismi esotici è un processo che avviene ormai da secoli ed è considerato a tutti gli effetti come una minaccia a livello globale. Dalla scoperta dell’America in Europa sono state introdotte circa 10.000 specie esotiche, principalmente piante e insetti. Tra questi ultimi hanno particolare rilevanza i coleotteri xilofagi, per lo più appartenenti alle famiglie scolitidi, cerambicidi e buprestidi. Questi insetti possono essere trasportati all’interno di pressoché qualsiasi tipo di materiale legnoso e, una volta arrivati e stabiliti nel nuovo ambiente, possono causare gravi danni al patrimonio forestale del paese di introduzione con gravi conseguenze sia sotto il profilo economico che ambientale. Da alcuni anni si è iniziato ad affiancare alle tradizionali metodologie di controllo diretto delle merci importate l’utilizzo di strumenti, quali trappole associate a sostanze attrattive, che permettono di aumentare le probabilità di intercettazione delle specie esotiche. Ad ogni modo, considerando le limitate risorse che vengono destinate per questo tipo di attività, diventa fondamentale avere a disposizione efficaci protocolli di monitoraggio ed individuare i punti a maggiore rischio di nuove introduzioni dove concentrare le risorse stesse. Questo non può però prescindere da una migliore conoscenza del processo di invasione biologica e delle tre fasi in cui esso viene comunemente diviso: l’arrivo, l’insediamento e la diffusione nel nuovo ambiente. Questa tesi si pone due obiettivi principali: il primo è quello di migliorare l’efficacia degli esistenti protocolli di monitoraggio al fine di aumentare le possibilità di intercettazione di specie esotiche di insetti del legno sia in aree costiere che continentali, mentre il secondo è quello di approfondire i meccanismi che guidano il processo di invasione biologica. Il primo studio riguarda lo sviluppo di un protocollo di monitoraggio utilizzabile per l’intercettazione di specie esotiche di insetti del legno nei porti europei e considera l’effetto di diverse tecniche di diffusione delle sostanze attrattive e di diversi modelli di trappole, nonché del loro posizionamento all’esterno o all’interno dell’area portuale, sulle possibilità di cattura delle specie esotiche stesse. I risultati indicano come l’utilizzo di trappole modello “multi-funnel”, attivate contemporanemante con più sostanze attrattive, rappresenti un’importante integrazione dei tradizionali metodi di ispezione. Essi inoltre suggeriscono l’impiego di trappole anche nelle aree circostanti il porto per rafforzare i programmi di monitoraggio. Il secondo studio indaga come il volume annuale di importazioni e il paesaggio circostante i porti, espresso in termini di copertura e tipologia forestale (conifere vs latifoglie), influenzano la cattura e l’intercettazione di specie esotiche di insetti del legno. I risultati dimostrano come il monitoraggio dovrebbe essere effettuato utilizzando trappole sia all’interno che all’esterno dell’area portuale, concentrando gli sforzi di campionamento nei porti che ricevono annualmente i volumi più elevati di merci e nei boschi misti di latifoglie localizzati nei primi chilometri attorno al porto. Il terzo studio confronta le catture di specie esotiche ottenute in aree portuali e in siti di riciclaggio o smaltimento di materiali legnosi, considerati come destinazione finale di parte degli imballaggi associati alle merci importate. Lo studio dimostra come tali siti possano essere considerati come utili punti da monitorare per aumentare le possibilità di intercettazione nelle aree continentali. Il quarto e quinto studio indagano il ruolo delle principali variabili climatiche e ambientali sui meccanismi ecologici che regolano il processo di stabilizzazione e diffusione di scolitidi esotici rispettivamente a scala regionale e continentale. I risultati dimostrano che il processo di invasione non è casuale e che sia le variabili climatiche, in termini di temperatura e precipitazioni, che la diversità ambientale, in termini di composizione forestale, giocano un ruolo fondamentale nel modellare le comunità di specie esotiche e la loro distribuzione nel nuovo ambiente, ma che questo avviene in modo differente nei due gruppi principali di coleotteri scolitidi, gli scolitidi xilematici e quelli floematici. Nel complesso, i cinque contributi di questa tesi forniscono indicazioni per aumentare le possibilità di intercettazione di specie esotiche di insetti del legno sia in aree costiere che continentali, descrivendo un approccio applicabile anche a scala internazionale. Allo stesso tempo contribuiscono ad approfondire i meccanismi che caratterizzano il processo di invasione degli insetti del legno, informazioni che risultano essere fondamentali in vista di futuri approcci applicativi volti alla riduzione dei danni ambientali ed economici attribuibili alle specie esotiche

Data for Mas et al. "Investigating beetle communities in and around entry points can improve surveillance at national and international scale"

The dataset reports the number of individuals collected using baited traps at ports and their surrounding areas for each of the five Spanish locations where the study was carried out. Data are reported for each year