Defining invasiveness and invasibility in ecological networks

The success of a biological invasion is context dependent, and yet two key concepts—the invasiveness of species and the invasibility of recipient ecosystems—are often defined and considered separately. We propose a framework that can elucidate the complex relationship between invasibility and invasiveness. It is based on trait-mediated interactions between species and depicts the response of an ecological network to the intrusion of an alien species, drawing on the concept of community saturation. Here, invasiveness of an introduced species with a particular trait is measured by its per capita population growth rate when the initial propagule pressure of the introduced species is very low. The invasibility of the recipient habitat or ecosystem is dependent on the structure of the resident ecological network and is defined as the total width of an opportunity niche in the trait space susceptible to invasion. Invasibility is thus a measure of network instability. We also correlate invasibility with the asymptotic stability of resident ecological network, measured by the leading eigenvalue of the interaction matrix that depicts trait-based interaction intensity multiplied by encounter rate (a pairwise product of propagule pressure of all members in a community). We further examine the relationship between invasibility and network architecture, including network connectance, nestedness and modularity. We exemplify this framework with a trait-based assembly model under perturbations in ways to emulate fluctuating resources and random trait composition in ecological networks. The maximum invasiveness of a potential invader (greatest intrinsic population growth rate) was found to be positively correlated with invasibility of the recipient ecological network. Additionally, ecosystems with high network modularity and high ecological stability tend to exhibit high invasibility. Where quantitative data are lacking we propose using a qualitative interaction matrix of the ecological network perceived by a potential invader so that the structural network stability and invasibility can be estimated from the literature or from expert opinion. This approach links network structure, invasiveness and invasibility in the context of trait-mediated interactions, such as the invasion of insects into mutualistic and antagonistic networks

Demography of an invading forest insect reunited with hosts and parasitoids from its native range

SUPPLEMENTARY MATERIALS : Explanation note: This file includes demographic data from native Sirex nigricornis woodwasps that were collected during our study. TABLE S1. Correlation matrix of bolt-level variables for P. resinosa and P. sylvestris. TABLE S2. Review of 10th and 90th percentile female body mass from insect species estimated from source paper cited, showing comparatively higher female S. noctilio body size variation. FIGURE S1. Examples of S. noctilio oviposition sites, lesion formation and emergence holes in the field. FIGURE S2. Top panels show a typical bolt from P. sylvestris with bark removed and S. noctilio emergence holes and oviposition sites identified. FIGURE S3. The number of S. noctilio emerging per tree was best described by a zero inflated negative binomial distribution (dotted line) with proportion of excess zeroes Φ = 0.32, μ = 75.39 and overdispersion parameter k = 0.35. FIGURE S4. Allometric relationships for S. noctilio in the Central NY data set: number of eggs and adult female mass (a; quantile regression), adult female mass and adult female length (b; fitted power function) and adult length and width of adult head capsule (c; linear regression).The Sirex woodwasp Sirex noctilio Fabricius (Hymenoptera: Siricidae), a widespread invasive pest of pines in the Southern Hemisphere, was first detected in North America in 2004. This study assessed the impacts of life history traits, host resistance and species interactions on the demography of S. noctilio in New York, Pennsylvania and Vermont, then compared key metrics to those found in the native range in Galicia, Spain. Many trees naturally attacked by S. noctilio in North America produced no adult woodwasps, with 5 of 38 infested trees (13%) sampled across six sites yielding 64% of emerging insects. Reproductive success was highest in the introduced host scots pine, Pinus sylvestris, but native red pine, Pinus resinosa, produced larger insects. Sirex noctilio required one or sometimes two years to develop and sex ratios were male biased, 1:2.98 ♀:♂. Body size and fecundity were highly variable, but generally lower than observed in non-native populations in the Southern Hemisphere. Hymenopteran parasitoids killed approximately 20% of S. noctilio larvae and 63% of emerging adults were colonized by the parasitic nematode Deladenus siricidicola, although no nematodes entered eggs. Demographic models suggested that S. noctilio in the northeastern USA have a higher potential for population growth than populations in the native range: estimated finite factor of increase, λ, was 4.17–4.52 (depending on tree species colonized), compared to λ = 1.57 in Spain.USDA Forest Service International Programs and OP RDE.https://neobiota.pensoft.netam2023Forestry and Agricultural Biotechnology Institute (FABI)Zoology and Entomolog

Biotic and abiotic effects on density, body size, sex ratio, and survival in immature stages of the European woodwasp, Sirex Noctilio

Resource quality can have direct or indirect effects on female oviposition choice, offspring growth and survival, and ultimately on body size and sex ratio. We examined these patterns in Sirex noctilio Fabricus, the globally invasive European pine woodwasp, in South African Pinus patula plantations. We studied how tree position as well as natural variation in biotic and abiotic factors influenced sex-specific density, larval size, tunnel length, male proportion, and survival across development. Twenty infested trees divided into top, middle, and bottom sections were sampled at three time points during larval development. We measured moisture content, bluestain fungal colonization, and co-occurring insect density and counted, measured, and sexed all immature wasps. A subset of larval tunnels was measured to assess tunnel length and resource use efficiency (tunnel length as a function of immature wasp size). Wasp density increased from the bottoms to the tops of trees for both males and females. However, the largest individuals and the longest tunnels were found in bottom sections. Male bias was strong (~10:1) and likewise differed among sections, with the highest proportion in the middle and top sections. Sex ratios became more strongly male biased due to high female mortality, especially in top and middle sections. Biotic and abiotic factors such as colonization by Diplodia sapinea, weevil (Pissodes sp.) density, and wood moisture explained modest residual variation in our primary mixed effects models (0%–22%). These findings contribute to a more comprehensive understanding of sex-specific resource quality for S. noctilio and of how variation in key biotic and abiotic factors can influence body size, sex ratio, and survival in this economically important woodwasp.The Tree Protection Cooperative Program at the Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, South Africa.http://www.ecolevol.orgpm2021Mammal Research InstituteZoology and Entomolog

Data from: Predictors of Phytophthora diversity and community composition in natural areas across diverse Australian ecoregions

Comprehensive understanding of the patterns and drivers of microbial diversity at a landscape scale is in its infancy, despite the recent ease by which soil communities can be characterized using massively parallel amplicon sequencing. Here we report on a comprehensive analysis of the drivers of diversity distribution and composition of the ecologically and economically important Phytophthora genus from 414 soil samples collected across Australia. We assessed 22 environmental and seven categorical variables as potential predictors of Phytophthora species richness, αandβ diversity, including both phylogenetically and non‐phylogenically explicit methods. In addition, we classified each species as putatively native or introduced and examined the distribution with respect to putative origin. The two most widespread species, P. multivora and P. cinamomi, are introduced, though five of the ten most widely distributed species are putatively native. Introduced taxa comprised over 54% of Australia's Phytophthora diversity and these species are known pathogens of annual and perennial crop habitats as well as urban landscapes and forestry. Patterns of composition were most strongly predicted by bioregion (R2=0.29) and ecoregion (R2=0.26) identity; mean precipitation of warmest quarter, mean temperature of the wettest quarter and latitude were also highly significant and described approximately 21%, 14% and 13% of variation in NMDS composition, respectively. We also found statistically significant evidence for phylogenetic over‐dispersion with respect to key climate variables.This study provides a strong baseline for understanding biogeographical patterns in this important genus as well the impact of key plant pathogens and invasive Phytophthora species in natural ecosystems

The global diversity of Deladenus siricidicola in native and non-native populations

The nematode Deladenus siricidicola is the primary biological control agent of Sirex noctilio, a globally invading woodwasp pest of Pinus species. Preliminary studies on the diversity of populations of D. siricidicola revealed very low diversity in the Southern Hemisphere where they have been introduced for the purpose of biological control. The potential to augment biocontrol efficacy by increasing genetic diversity in biocontrol programs motivated this study, which investigated the patterns of genetic diversity in D. siricidicola across eight countries, including the presumed native range (Spain), areas of accidental introduction (Canada and the USA) and countries D. siricidicola has been intentionally released (Argentina, Brazil, Chile, New Zealand and South Africa). Nematodes were screened using mitochondrial COI sequence data and twelve microsatellite markers. Analyses of these data identified three distinct lineages from North America (Lineage A), the Southern Hemisphere (Lineage B) and Spain (Lineage C). Strains from Chile were an exception as they appear to represent an admixture of lineages A and B. This suggests a common origin of populations throughout the Southern Hemisphere, with a second introduction from North America into Chile. The introduction into North America is distinct from that in the Southern Hemisphere and probably originated from Europe. It is evident that substantial genetic diversity exists in D. siricidicola globally, which could be exploited to augment the reduced diversity in some populations used in biocontrol programs.The University of Pretoria, members of the Tree Protection Co-operative Program (TPCP), South Africa, and USDA Forest Service International Programs.http://www.elsevier.com/locate/ybcon2020-05-01hj2019BiochemistryForestry and Agricultural Biotechnology Institute (FABI)GeneticsMicrobiology and Plant PathologyZoology and Entomolog

Current status of the Botryosphaeriaceae in Australia

The Botryosphaeriales, and in particular the Botryosphaeriaceae, are a well-studied group of fungi best known for the canker diseases they cause on woody hosts especially in stressed or damaged trees. Australian Plant Pathology herbaria contain many records for this group, but due to considerable taxonomic changes over the past decade, many of the species names have since been reclassified. In this article we used all published records with available sequence data of the Botryosphaeriaceae in Australia to examine the distribution and host range of these taxa. There are 24 genera encompassing 222 species in the Botryosphaeriaceae; 9 genera and 62 species have been recorded in Australia. Some genera such as Neoscytalidium are only found in warm, humid climates while Dothiorella species are more common in temperate climates. There were species, such as Lasiodiplodia theobromae, Neofusicoccum parvum and Botryosphaeria dothidea, which had a wide host range with many records. However, there were also several species found only in one location on a single host. While systematic data collection is still required, the information presented here provides a baseline of species present in Australia and will underpin future studies into this group of important pathogens

Aggressive tree killer or natural thinning agent? Assessing the impacts of a globally important forest insect

Invasive insects and pathogens are prominent tree mortality agents in forests around the world, and the magnitude of their impacts is increasing. Comparative studies across multiple populations can be helpful for the development of new insights and innovative management strategies. We used the Sirex woodwasp, Sirex noctilio Fabricius, as a model system to compare invasion impacts across a range of ecological contexts around the globe: native woodwasps colonizing native trees, invasive woodwasps in non-native plantation trees, and invasive woodwasps attacking native trees. Across 133 stands of eight pine species on four continents, tree mortality associated with S. noctilio attack was positively correlated with stand basal area and stand density, and was mostly confined to smaller, suppressed trees. Larger average tree size and greater distances between trees were linked to lower levels of tree mortality. To more deeply assess the impacts of tree loss due to this pest, we examined mortality in vigorous trees, defined as those with a stem diameter greater than or equal to 90% of the mean diameter for trees in the stand. Sirex noctilio- related mortality in vigorous trees was rare, with one exception where Pinus contorta stands in Argentina lost as many as 300 vigorous trees ha1. Pine species varied dramatically in their susceptibility to S. noctilio: for example, these losses in P. contorta were in stark contrast to very low mortality in P. ponderosa, the other pine species grown in Argentina. Surprisingly, location did not alter patterns in the influence of stand basal area on tree susceptibility for individual species. Most notably, Pinus radiata had the same relationship between basal area and tree mortality when grown in Spain (where S. noctilio is native and not considered a meaningful forest pest) and South Africa (where S. noctilio is a problematic invasive). Our findings suggest that the availability of optimal pine hosts is a key driver of S. noctilio-related tree mortality across continents and management regimes. Important variables that influence host availability include speciesspecific susceptibility and environmental and management-related factors that promote or limit the number of stressed trees present both within stands and across the regional forest or plantation landscape.Estación Experimental Agropecuaria BarilocheFil: Krivak-Tetley, Flora E. Dartmouth College. Department of Biological Sciences; Estados UnidosFil: Lantschner, Maria Victoria. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Lantschner, Maria Victoria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Lombardero, Maria J. Universidad de Santiago de Compostela. Escuela Politecnica Superior de Ingeniería; EspañaFil: Garnas, Jeff R. University of New Hampshire. Department of Natural Resources and the Environment; Estados UnidosFil: Hurley, Brett P. University of Pretoria. Department of Zoology and Entomology, Forestry and Agricultural Biotechnology Institute (FABI); SudáfricaFil: Villacide, Jose Maria. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Villacide, Jose Maria. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Slippers, Bernard. University of Pretoria. Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI); SudáfricaFil: Corley, Juan Carlos. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Bariloche; ArgentinaFil: Corley, Juan Carlos. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Liebhold, Andrew M. USDA Forest Service Northern Research Station; Estados UnidosFil: Ayres, Matthew P. Dartmouth College. Department of Biological Sciences; Estados Unido

Invasive Insects in Forest Plantations of Argentina: Ecological Patterns and Implications for Management

In the last decades, growing international trade and tourism have significantly increased the rate at which non-native species reach new ecosystems. Plantation forest systems in Argentina are especially exposed to alien insects partly because they are dominated by pines and eucalypts which have been introduced to produce timber and pulp, based, among other things, on the benefits related to the lack of native herbivores (i.e., the ?natural enemy release hypothesis?). As noted worldwide, with rising numbers of invasions by nonindigenous forest insects, strong negative economic and ecological impacts on the invaded ecosystems often come along. Notably, the most damaging non-native forest insects found in plantation forestry in Argentina are common to other areas and regions of the Southern Hemisphere, which cultivate similar tree species. By focusing on processes behind described patterns of arrival, establishment, and spread of alien forest insects in commercial forests of Argentina, we explore broad ecological patterns involved in their invasion success and how these may affect strategies of alien pest management.Fil: Corley, Juan Carlos. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentina. Universidad Nacional del Comahue. Centro Regional Universitario Bariloche. Departamento de Ecología; ArgentinaFil: Villacide, José María. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; ArgentinaFil: Lantschner, María Victoria. Instituto Nacional de Tecnología Agropecuaria. Centro Regional Patagonia Norte. Estación Experimental Agropecuaria San Carlos de Bariloche. Instituto de Investigaciones Forestales y Agropecuarias Bariloche. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigaciones Forestales y Agropecuarias Bariloche; Argentin