Tree-killing bark beetles are the most economically important insects in conifer forests worldwide. However, despite >200 years of research, the drivers of population eruptions and crashes are still ...not fully understood and the existing knowledge is thus insufficient to face the challenges posed by the Anthropocene. We critically analyze potential biotic and abiotic drivers of population dynamics of an exemplary species, the European spruce bark beetle (ESBB) (Ips typographus) and present a multivariate approach that integrates the many drivers governing this bark beetle system. We call for hypothesis-driven, large-scale collaborative research efforts to improve our understanding of the population dynamics of this and other bark beetle pests. Our approach can serve as a blueprint for tackling other eruptive forest insects.
Bark beetles are currently causing unprecedented damage to European and North American forests.Their population dynamics rarely have been studied in a hypothesis-driven manner incorporating exogenous biotic variables.We propose a conceptual framework to reveal the drivers of bark beetle populations.This approach can be equally applied to other eruptive insect pests.
Key message
Unprecedented forest declines and diebacks are expected worldwide in response to global change. Insects can trigger or contribute to these disturbances, which can in turn have either ...beneficial or detrimental retroactive cascading effects on insect communities. However, we are still unsure of the effects that pests will have on these disturbances in the future, and new biodiversity and pest management strategies still need to be put into place. Several recent contributions to Annals of Forest Science address these issues.
Key message
Decline can affect the structure, resources, and microclimates of the forest canopy, and potentially have cascading effects on canopy-dwelling species. Our survey shows that an oak ...decline can promote saproxylic beetles, especially xylophagous ones, and generalist phyllophagous weevils. However, it negatively affects specialist leaf-eating species and has no effect on seed-eating weevils.
Context
Decline in a context of climate change is expected to induce considerable changes in forest structure, potentially affecting habitat opportunities and trophic resources for numerous species. Nonetheless, the consequences of decline in forest biodiversity have rarely been studied.
Aims
We aimed to characterize the impact of oak decline on different guilds of canopy-dwelling beetles.
Methods
Beetles were sampled for three consecutive years in oak stands exhibiting different levels of decline. Several guilds were considered: (i) Buprestidae, (ii) other saproxylic beetles split into wood-boring species and non-wood-boring species, (iii) seed-eating weevils, and (iv) specialist and generalist leaf-eating weevils.
Results
Overall, decline had positive effects on the abundance and biomass of beetles, though contrasting variations were observed at the species or guild levels. Wood-boring species, especially the main oak-associated buprestids, and other saproxylic species benefitted from decline conditions. However, at odds with the insect performance hypothesis, decline had a positive effect on generalist leaf-eating species, a negative effect on specialist leaf-eating species, and a null effect on seed-eating species.
Conclusion
The increase in species richness for saproxylic and leaf-eating beetle communities suggests that decline might promote forest biodiversity. Our results call for further studies to thoroughly assess the functional outcomes of forest decline and to suggest management strategies for conservation biologists.
Abstract
The genus
Agrilus
is one of the most diverse insect genera worldwide. The larval feeding activity causes extensive damage in both forests and orchards. In addition, more than 30 species have ...been introduced outside their native range so far, including the emerald ash borer
Agrilus planipennis
Fairmaire. Thus, the availability of efficient trapping protocols for early detection of
Agrilus
species at entry points is of utmost importance. In this study we tested whether trapping protocols developed for surveillance of
A. planipennis
in North America were also effective for other
Agrilus
species. In particular, through a multi-country assessment we compared the efficacy of detecting
Agrilus
species on: (i) green glue-coated prism traps vs. green Fluon-coated multi-funnel traps when baited with the green leaf volatile (
Z
)-3-hexenol or left unbaited; and (ii) green multi-panel traps vs. green multi-panel traps baited with dead adult
Agrilus
beetles (decoys). A total of 23,481 individuals from 45
Agrilus
species were caught. Trap design significantly affected both species richness and abundance of
Agrilus
species in several of the countries where the trapping experiments were carried out, and green prism traps outperformed green multi-funnel traps in most cases. On the contrary, the addition of a (
Z
)-3-hexenol lure or dead adult beetle decoys on to traps did not improve trap catches. Our study highlights that reliable trap models to survey
Agrilus
species are already available, but also that there is the clear need to further investigate chemical ecology of
Agrilus
species to develop semiochemical lures that can improve detection efficacy.
There is tremendous diversity of interactions between plants and other species. These relationships range from antagonism to mutualism. Interactions of plants with members of their ecological ...community can lead to a profound metabolic reconfiguration of the plants’ physiology. This reconfiguration can favour beneficial organisms and deter antagonists like pathogens or herbivores. Determining the cellular and molecular dialogue between plants, microbes, and insects, and its ecological and evolutionary implications is important for understanding the options for each partner to adopt an adaptive response to its biotic environment. Moving forward, understanding how such ecological interactions are shaped by environmental change and how we potentially mitigate deleterious effects will be increasingly important. The development of integrative multidisciplinary approaches may provide new solutions to the major ecological and societal issues ahead of us. The rapid evolution of technology provides valuable tools and opens up novel ways to test hypotheses that were previously unanswerable, but requires that scientists master these tools, understand potential ethical problems flowing from their implementation, and train new generations of biologists with diverse technical skills. Here, we provide brief perspectives and discuss future promise and challenges for research on insect–plant interactions building on the 16th International Symposium on Insect–Plant interactions (SIP) meeting that was held in Tours, France (2–6 July 2017). Talks, posters, and discussions are distilled into key research areas in insect–plant interactions, highlighting the current state of the field and major challenges, and future directions for both applied and basic research.
There is tremendous diversity of interactions between plants and other species, ranging from antagonism to mutualism. Determining the cellular and molecular dialogue between plants, microbes, and insects, and its ecological and evolutionary implications is important. Integrative multidisciplinary approaches and the rapid evolution of technology may provide new solutions to the major ecological and societal issues ahead of us. This article reviews the major ground‐breaking themes that have been identified as promising and challenging issues in studies on insect–plant interactions.
1. Variations in developmental conditions of bark beetles, particularly intraspecific competition, can induce morphological and physiological modifications in the offspring. It is hypothesised that ...intraspecific competition could also affect host selection behaviour. Such behavioural changes might be manifested in response to host (alpha-pinene) or beetle (verbenone) compounds. 2. Ips pini were bred at different densities. The offspring were measured for size, weight, and lipid concentration, and then subjected to tunnelling bioassays in agar media amended with varying amounts of alpha-pinene or verbenone. 3. High parental colonisation densities reduced emergence time of parents and offspring. Increasing colonisation density and emergence time had a negative influence on offspring vigour, resulting in a reduction of the distance tunnelled by the beetles. 4. Both alpha-pinene and verbenone were repellent. Surprisingly, verbenone was also toxic at high concentrations, with its effect being greater on beetles arising from high densities. The repellent effect of these compounds did not vary according to colonisation density, but for both compounds, at a 1.5 mg g⁻¹ concentration, it increased with emergence time. 5. The consequences of varying vigour and behaviour in relation to developmental conditions and emergence patterns on population dynamics of I. pini are discussed.
The SoilTemp database will identify the microhabitats that best buffer the amplitude of warming. The temperature heterogeneity at spatial scales below the meter also requires attention. A worldwide ...database of temperatures near any surface is still lacking.
This article is a Commentary on Lembrechts et al., 26, 6616‐6629.
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