scholarly journals Evolving symbioses between insects and fungi that kill trees in Canada: new threats associated with invasive organisms

2016 ◽  
Vol 148 (S1) ◽  
pp. S160-S169 ◽  
Author(s):  
Tod D. Ramsfield
Keyword(s):  
Tree Mortality ◽  
Forest Ecosystems ◽  
Larval Feeding ◽  
Invasive Insects ◽  
Symbiotic Relationships ◽  
Direct Damage ◽  
Invasive Organisms ◽  
Forested Landscapes ◽  
Evolutionary Trajectories ◽  
Symbiotic Fungi

AbstractSymbiotic relationships between insects and fungi are known to cause tree mortality either through direct damage by larval feeding that can be facilitated by symbiotic fungi, or through insects vectoring pathogens directly to healthy trees. Within their native ranges, the impacts of many insect-fungus symbioses are restricted to weakened and declining trees; however, within the last century tree mortality caused by globally invasive insect–fungus associations has had a devastating impact on trees in both urban and natural forest ecosystems. Unfortunately, Canadian forests have been seriously affected by invasive organisms and an emerging threat is the expansion of a native bark beetle into the boreal forest of Alberta. This paper reviews the symbiotic relationships between selected invasive insects and pathogens that cause tree mortality within the urban and forested landscapes of Canada; it uses these case studies to illustrate potentially damaging new evolutionary trajectories.

scholarly journals Fungal-Fungal Interactions in Leaf-Cutting Ant Agriculture

2011 ◽  
Vol 2011 ◽  
pp. 1-9 ◽  
Author(s):  
Sunshine A. Van Bael ◽  
Catalina Estrada ◽  
William T. Wcislo
Keyword(s):  
Plant Traits ◽  
Secondary Compounds ◽  
Future Research ◽  
Ecological Interactions ◽  
Tropical Plants ◽  
Symbiotic Relationships ◽  
Complex Interactions ◽  
Symbiotic Fungi ◽  
Leaf Cutting ◽  
Fungal Interactions

Many organisms participate in symbiotic relationships with other organisms, yet studies of symbioses typically have focused on the reciprocal costs and benefits within a particular host-symbiont pair. Recent studies indicate that many ecological interactions involve alliances of symbionts acting together as mutualistic consortia against other consortia. Such interacting consortia are likely to be widespread in nature, even if the interactions often occur in a cryptic fashion. Little theory and empirical data exist concerning how these complex interactions shape ecological outcomes in nature. Here, we review recent work on fungal-fungal interactions between two consortia: (i) leaf-cutting ants and their symbiotic fungi (the latter grown as a food crop by the former) and (ii) tropical plants and their foliar endophytes (the cryptic symbiotic fungi within leaves of the former). Plant characteristics (e.g., secondary compounds or leaf physical properties of leaves) are involved in leaf-cutting ant preferences, and a synthesis of published information suggests that these plant traits could be modified by fungal presence. We discuss potential mechanisms for how fungal-fungal interactions proceed in the leaf-cutting ant agriculture and suggest themes for future research.

scholarly journals Laurel Wilt: Current and Potential Impacts and Possibilities for Prevention and Management

Forests ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 181
Author(s):  
Rabiu O. Olatinwo ◽  
Stephen W. Fraedrich ◽  
Albert E. Mayfield
Keyword(s):  
United States ◽  
Tree Mortality ◽  
The United States ◽  
Persea Americana ◽  
Laurel Wilt ◽  
Important Species ◽  
Invasive Insects ◽  
Raffaelea Lauricola ◽  
Redbay Ambrosia Beetle ◽  
The Impact

In recent years, outbreaks of nonnative invasive insects and pathogens have caused significant levels of tree mortality and disturbance in various forest ecosystems throughout the United States. Laurel wilt, caused by the pathogen Raffaelea lauricola (T.C. Harr., Fraedrich and Aghayeva) and the primary vector, the redbay ambrosia beetle (Xyleborus glabratus Eichhoff), is a nonnative pest-disease complex first reported in the southeastern United States in 2002. Since then, it has spread across eleven southeastern states to date, killing hundreds of millions of trees in the plant family Lauraceae. Here, we examine the impacts of laurel wilt on selected vulnerable Lauraceae in the United States and discuss management methods for limiting geographic expansion and reducing impact. Although about 13 species belonging to the Lauraceae are indigenous to the United States, the highly susceptible members of the family to laurel wilt are the large tree species including redbay (Persea borbonia (L.) Spreng) and sassafras (Sassafras albidum (Nutt.) Nees), with a significant economic impact on the commercial production of avocado (Persea americana Mill.), an important species native to Central America grown in the United States. Preventing new introductions and mitigating the impact of previously introduced nonnative species are critically important to decelerate losses of forest habitat, genetic diversity, and overall ecosystem value.

scholarly journals Plant Secondary Metabolism: Diversity, Function and its Evolution

2008 ◽  
Vol 3 (8) ◽  
pp. 1934578X0800300 ◽  
Author(s):  
Michael Wink
Keyword(s):  
Secondary Metabolites ◽  
Main Function ◽  
Symbiotic Relationships ◽  
Pathway Gene ◽  
Interesting Pattern ◽  
Differential Gene Regulation ◽  
Symbiotic Fungi ◽  
Differential Gene ◽  
Taxonomic Groups ◽  
Occurrence Patterns

A typical character of plants is the production and storage of usually complex mixtures of secondary metabolites (SM). The main function of secondary metabolites is defense against herbivores and microbes; some SM are signal compounds to attract pollinating and seed dispersing animals or play a role in the symbiotic relationships with plants and microbes. The distribution of SM in the plant kingdom shows an interesting pattern. A specific SM is often confined to a particular systematic unit, but isolated occurrences can occur in widely unrelated taxonomic groups. This review tries to explain the patchy occurrence of SM in plants. It could be due to convergent evolution, but evidence is provided that the genes that encode the biosynthesis of SM appear to have a much wider distribution than the actual secondary metabolite. It seems to be rather a matter of differential gene regulation whether a pathway is active and expressed in a given taxonomic unit or not. It is speculated that the genes of some pathways derived from an early horizontal gene transfer from bacteria, which later became mitochondria and chloroplasts. These genes/pathways should be present in most if not all land plants. About 80% of plants live in close symbiotic relationships with symbiotic fungi (ectomycorrhiza, endophytes). Recent evidence is presented that these fungi can either directly produce SM, which were formerly considered as plant SM or that these fungi have transferred the corresponding pathway gene to the host plant. The fungal contribution could also explain part of the patchy occurrence patterns of several secondary metabolites.

scholarly journals Dynamic Responses of Ground-Dwelling Invertebrate Communities to Disturbance in Forest Ecosystems

Insects ◽  
2019 ◽  
Vol 10 (3) ◽  
pp. 61 ◽  
Author(s):  
Kayla Perry ◽  
Daniel Herms
Keyword(s):  
Forest Ecosystems ◽  
Environmental Changes ◽  
Woody Debris ◽  
Canopy Structure ◽  
Dynamic Responses ◽  
Gap Formation ◽  
Invasive Insects ◽  
Salvage Logging ◽  
Invertebrate Communities ◽  
Debris Accumulation

In forest ecosystems, natural and anthropogenic disturbances alter canopy structure, understory vegetation, amount of woody debris, and the properties of litter and soil layers. The magnitude of these environmental changes is context-dependent and determined by the properties of the disturbance, such as the frequency, intensity, duration, and extent. Therefore, disturbances can dynamically impact forest communities over time, including populations of ground-dwelling invertebrates that regulate key ecosystem processes. We propose conceptual models that describe the dynamic temporal effects of canopy gap formation and coarse woody debris accumulation following disturbances caused by invasive insects, wind, and salvage logging, and their impacts on ground-dwelling invertebrate communities. Within this framework, predictions are generated, literature on ground-dwelling invertebrate communities is synthesized, and pertinent knowledge gaps identified.

scholarly journals The sudden emergence of pathogenicity in insect–fungus symbioses threatens naive forest ecosystems

2011 ◽  
Vol 278 (1720) ◽  
pp. 2866-2873 ◽  
Author(s):  
Jiri Hulcr ◽  
Robert R. Dunn
Keyword(s):  
Tree Mortality ◽  
Forest Ecosystems ◽  
Current Understanding ◽  
Large Majority ◽  
Invasive Insect ◽  
Significant Damage ◽  
The World ◽  
Bark And Ambrosia Beetles ◽  
Diverse Community ◽  
Wood Boring

Invasive symbioses between wood-boring insects and fungi are emerging as a new and currently uncontrollable threat to forest ecosystems, as well as fruit and timber industries throughout the world. The bark and ambrosia beetles (Curculionidae: Scolytinae and Platypodinae) constitute the large majority of these pests, and are accompanied by a diverse community of fungal symbionts. Increasingly, some invasive symbioses are shifting from non-pathogenic saprotrophy in native ranges to a prolific tree-killing in invaded ranges, and are causing significant damage. In this paper, we review the current understanding of invasive insect–fungus symbioses. We then ask why some symbioses that evolved as non-pathogenic saprotrophs, turn into major tree-killers in non-native regions. We argue that a purely pathology-centred view of the guild is not sufficient for explaining the lethal encounters between exotic symbionts and naive trees. Instead, we propose several testable hypotheses that, if correct, lead to the conclusion that the sudden emergence of pathogenicity is a new evolutionary phenomenon with global biogeographical dynamics. To date, evidence suggests that virulence of the symbioses in invaded ranges is often triggered when several factors coincide: (i) invasion into territories with naive trees, (ii) the ability of the fungus to either overcome resistance of the naive host or trigger a suicidal over-reaction, and (iii) an ‘olfactory mismatch’ in the insect whereby a subset of live trees is perceived as dead and suitable for colonization. We suggest that individual cases of tree mortality caused by invasive insect–fungus symbionts should no longer be studied separately, but in a global, biogeographically and phylogenetically explicit comparative framework.

scholarly journals Local forest structure variability increases resilience to wildfire in dry western U.S. coniferous forests

2019 ◽  
Author(s):  
Michael J Koontz ◽  
Malcolm P. North ◽  
Chhaya M. Werner ◽  
Stephen E. Fick ◽  
Andrew M. Latimer
Keyword(s):  
Sierra Nevada ◽  
Forest Structure ◽  
Tree Mortality ◽  
Forest Ecosystems ◽  
Fire Suppression ◽  
Fire Severity ◽  
Fire Behavior ◽  
Dry Forest ◽  
Structural Variability ◽  
Overstory Trees

A “resilient” forest endures disturbance and is likely to persist. Resilience to wildfire may arise from feedback between fire behavior and forest structure in dry forest systems. Frequent fire creates fine-scale variability in forest structure, which may then interrupt fuel continuity and prevent future fires from killing overstory trees. Testing the generality and scale of this phenomenon is challenging for vast, long-lived forest ecosystems. We quantify forest structural variability and fire severity across >30 years and >1,000 wildfires in California’s Sierra Nevada. We find that greater variability in forest structure increases resilience by reducing rates of fire-induced tree mortality and that the scale of this effect is local, manifesting at the smallest spatial extent of forest structure tested (90 x 90m). Resilience of these forests is likely compromised by structural homogenization from a century of fire suppression, but could be restored with management that increases forest structural variability.

scholarly journals Assessing hurricane-induced tree mortality in U.S. Gulf Coast forest ecosystems

2010 ◽  
Vol 115 (G4) ◽  
Author(s):  
Robinson Negrón-Juárez ◽  
David B. Baker ◽  
Hongcheng Zeng ◽  
Theryn K. Henkel ◽  
Jeffrey Q. Chambers
Keyword(s):  
Tree Mortality ◽  
Forest Ecosystems ◽  
Gulf Coast

Mutual interactions between an invasive bark beetle and its associated fungi

2011 ◽  
Vol 102 (1) ◽  
pp. 71-77 ◽  
Author(s):  
B. Wang ◽  
C. Salcedo ◽  
M. Lu ◽  
J. Sun
Keyword(s):  
Feeding Activity ◽  
Larval Mortality ◽  
Fungal Growth ◽  
Egg Laying ◽  
Larval Feeding ◽  
Forest Pest ◽  
Volatile Chemicals ◽  
Invasive Insects ◽  
Fungal Associates ◽  
Leptographium Terebrantis

AbstractInteractions between invasive insects and their fungal associates have important effects on the behavior, reproductive success, population dynamics and evolution of the organisms involved. The red turpentine beetle (RTB), Dendroctonus valens LeConte (Coleoptera: Scolytinae), an invasive forest pest in China, is closely associated with fungi. By carrying fungi on specialized structures in the exoskeleton, RTB inoculates fungi in the phloem of pines (when females dig galleries for egg laying and when males join them for mating). After eggs hatch, larvae gregariously feed on the phloem colonized by the fungi. We examined the effects of five isolates of RTB associated fungi (two from North America, Leptographium terebrantis and L. procerum, and three from China, Ophiostoma minus, L. sinoprocerum and L. procerum) on larval feeding activity, development and mortality. We also studied the effects of volatile chemicals produced in the beetle hindgut on fungal growth. Ophiostoma minus impaired feeding activity and reduced weight in RTB larvae. Leptographium sinoprocerum, L. terebrantis and L. procerum did not dramatically influence larval feeding and development compared to fungi-free controls. Larval mortality was not influenced by any of the tested fungi. Hindgut volatiles of RTB larvae, verbenol, myrtenol and myrtenal, inhibited growth rate of all the fungi. Our results not only show that D. valens associated fungus, O. minus, can be detrimental to its larvae; but, most importantly, they also show that these notorious beetles have an outstanding adaptive response evidenced by the ability to produce volatiles that inhibit growth of harmful fungus.

Forest dynamics after drought-induced mortality: a global assessment

2020 ◽  
Author(s):  
Enric Batllori Presas ◽  
Francisco Lloret Maya
Keyword(s):  
Forest Dynamics ◽  
Global Assessment ◽  
Temperate Forest ◽  
Tree Mortality ◽  
Forest Ecosystems ◽  
Species Traits ◽  
Short Term ◽  
Management Intensity ◽  
Dry Conditions ◽  
Study Sites

<p>Forest mortality related to extreme drought has been reported worldwide, affecting all biomes and plant types (angiosperm vs. gymnosperms, evergreen vs. deciduous). The forecasted increased frequency and intensity of drought events as a consequence of anthropogenic climate change could promote an increasingly widespread drought-induced mortality in the future. However, little understanding exists on ecological trajectories or the replacement processes after drought-induced mortality events. We assess (through a collaborative initiative) the extent of short-term self-replacement patterns in temperate forest ecosystems worldwide (N = 131 sites) in relation to: species traits, the major bioclimatic characteristics of reporting sites, and past management and disturbance legacies in the affected sites. We found that alternate species replaced pre-drought dominant tree species in ~70% of the examined cases, whereas in ~10% of the study sites there was no replacement by woody vegetation. Replacement was influenced by management intensity, and post-drought shrub dominance was higher when pathogens acted as co-drivers of tree mortality. No significant replacement patterns were found in relation to the bioclimatic characteristics of the reporting sites (environmental location) or of the dominant species (bioclimatic ‘niche’). Shifts to both more xeric and to moister communities were observed. These changes were driven by species with higher limits of tolerance to dry conditions and by species with wider bioclimatic ranges, respectively. Overall, our findings highlight the potential for major forest ecosystem reorganization in the coming decades.</p>

A spatio-temporal analysis of the relationship between housing renovation, socioeconomic status, and urban forest ecosystems

2018 ◽  
Vol 46 (6) ◽  
pp. 1115-1131 ◽  
Author(s):  
James WN Steenberg ◽  
Pamela J Robinson ◽  
Peter N Duinker
Keyword(s):  
Tree Mortality ◽  
Forest Ecosystems ◽  
Urban Forest ◽  
Common Knowledge ◽  
Canopy Cover ◽  
Ordinary Least Squares ◽  
Tree Planting ◽  
Least Squares Regression ◽  
Building Permit ◽  
The Relationship

Urban forest ecosystems are increasingly recognized as necessary components of a city's overall sustainability. The number of municipal governments planning and implementing urban forest management programs is rising, as the benefits of urban forest ecosystems are becoming common knowledge. However, the urban forest is an exceedingly complex and vulnerable social–ecological system that presents a wide array of management challenges. One area of concern that is understudied and worthy of investigation is the effects of housing renovation activities and neighborhood revitalization on the urban forest. The purpose of this study is to investigate the possibility of renovation activity as a significant source of disturbance in urban forest ecosystems. We conducted ordinary least squares regression and geographically weighted regression analyses using canopy cover, building permit data, and socioeconomic variables in Toronto, Canada. We then conducted a parcel-level assessment of tree mortality using ortho-imagery from 2003 and 2014 and government open data describing 16 years of renovation activity. Findings suggest that renovation activity, as indicated by building permit abundance, is a possible cause of tree mortality and subsequently a source of urban forest disturbance. Our findings also suggest that the relationship between renovation activity and canopy cover is highly complex, and is likely influenced by residential tree planting rates, land use mix, and different trajectories of urban change.

Sign in / Sign up

Export Citation Format

Share Document