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1. Reciprocal human-natural system feedback loops within the invasion process

   https://doi.org/10.3897/neobiota.62.52664  

   Sinclair, James S. ; Brown, Jeffrey A. ; Lockwood, Julie L. ( October 2020 , NeoBiota)

   null (Ed.)

   Biological invasions are inextricably linked to how people collect, move, interact with and perceive non-native species. However, invasion frameworks generally do not consider reciprocal interactions between non-native species and people. Non-native species can shape human actions via beneficial or detrimental ecological and socioeconomic effects and people, in turn, shape invasions through their movements, behaviour and how they respond to the collection, transport, introduction and spread of non-natives. The feedbacks that stem from this ‘coupled human and natural system’ (CHANS) could therefore play a key role in mitigating (i.e. negative feedback loops) or exacerbating (i.e. positive feedback loops) ongoing and future invasions. We posit that the invasion process could be subdivided into three CHANS that span from the source region from which non-natives originate to the recipient region in which they establish and spread. We also provide specific examples of feedback loops that occur within each CHANS that have either reduced or facilitated new introductions and spread of established non-native species. In so doing, we add to exisiting invasion frameworks to generate new hypotheses about human-based drivers of biological invasions and further efforts to determine how ecological outcomes feed back into human actions. 

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2. Tree diversity regulates forest pest invasion

   https://doi.org/10.1073/pnas.1821039116  

   Guo, Qinfeng ; Fei, Songlin ; Potter, Kevin M. ; Liebhold, Andrew M. ; Wen, Jun ( March 2019 , Proceedings of the National Academy of Sciences)

   Nonnative pests often cause cascading ecological impacts, leading to detrimental socioeconomic consequences; however, how plant diversity may influence insect and disease invasions remains unclear. High species diversity in host communities may promote pest invasions by providing more niches (i.e., facilitation), but it can also diminish invasion success because low host dominance may make it more difficult for pests to establish (i.e., dilution). Most studies to date have focused on small-scale, experimental, or individual pest/disease species, while large-scale empirical studies, especially in natural ecosystems, are extremely rare. Using subcontinental-level data, we examined the role of tree diversity on pest invasion across the conterminous United States and found that the tree-pest diversity relationships are hump-shaped. Pest diversity increases with tree diversity at low tree diversity (because of facilitation or amplification) and is reduced at higher tree diversity (as a result of dilution). Thus, tree diversity likely regulates forest pest invasion through both facilitation and dilution that operate simultaneously, but their relative strengths vary with overall diversity. Our findings suggest the role of native species diversity in regulating nonnative pest invasions.

    

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3. Cities Shape the Diversity and Spread of Nonnative Species

   https://doi.org/10.1146/annurev-ecolsys-102722-012749  

   Potgieter, Luke J ; Li, Daijiang ; Baiser, Benjamin ; Kühn, Ingolf ; Aronson, Myla FJ ; Carboni, Marta ; Celesti-Grapow, Laura ; de_Matos, Ana_Carolina L ; Lososová, Zdeňka ; Montaño-Centellas, Flavia A ; et al ( August 2024 , Annual Review of Ecology, Evolution, and Systematics)

   The globalization of trade and increased human mobility have facilitated the introduction and spread of nonnative species, posing significant threats to biodiversity and human well-being. As centers of global trade and human populations, cities are foci for the introduction, establishment, and spread of nonnative species. We present a global synthesis of urban characteristics that drive biological invasions within and across cities, focusing on four axes: (a) connectivity, (b) physical properties, (c) culture and socioeconomics, and (d) biogeography and climate. Urban characteristics such as increased connectivity within and among cities, city size and age, and wealth emerged as important drivers of nonnative species diversity and spread, while the relative importance of biogeographic and climate drivers varied considerably. Elaborating how these characteristics shape biological invasions in cities is crucial for designing and implementing strategies to mitigate the impacts of invasions on ecological systems and human well-being.

    

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4. Inoculation with native soil improves seedling survival and reduces non‐native reinvasion in a grassland restoration

   https://doi.org/10.1111/rec.13685  

   Duell, Eric B. ; O'Hare, Anna ; Wilson, Gail W. T. ( April 2022 , Restoration Ecology)

   Losses of grasslands have been largely attributed to widespread land‐use changes, such as conversion to row‐crop agriculture. The remaining tallgrass prairie faces further losses due to biological invasions by non‐native plant species, often with resultant ecosystem degradation. Of critical concern for conservation, restoration of native grasslands has been met with little success following eradication of non‐native plants. In addition to the direct and indirect effects of non‐native invasive plants on beneficial soil microbes, management practices targeting invasive species may also negatively affect subsequent restoration efforts. To assess mechanisms limiting germination and survival of native species and to improve native species establishment, we established six replicate plots of each of the following four treatments: (1) inoculated with freshly collected prairie soil with native seeds; (2) inoculated with steam‐pasteurized soil with native seeds; (3) noninoculated with native seeds; or (4) noninoculated/nonseeded control. Inoculation with whole soil did not improve seed germination; however, addition of whole soil significantly improved native species survival, compared to pasteurized soil or noninoculated treatments. Inoculation with whole soil significantly decreased reestablishment of non‐native invasiveBothriochloa bladhii(Caucasian bluestem); at the end of the growing season, plots receiving whole soil consisted of approximately 30%B. bladhiicover, compared to approximately 80% in plots receiving no soil inoculum. Our results suggest invasion and eradication efforts negatively affect arbuscular mycorrhizal hyphal and spore abundances and soil aggregate stability, and inoculation with locally adapted soil microbial communities can improve metrics of restoration success, including plant species richness and diversity, while decreasing reinvasion by non‐native species.

    

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5. Spatial patterns of discovery points and invasion hotspots of non‐native forest pests

   https://doi.org/10.1111/geb.12988  

   Ward, Samuel_F ; Fei, Songlin ; Liebhold, Andrew_M ; Keil, ed., Petr ( August 2019 , Global Ecology and Biogeography)

   Establishments of non‐native forest pests (insects and pathogens) continue to increase worldwide with growing numbers of introductions and changes in invasion pathways. Quantifying spatio‐temporal patterns in establishment locations and subsequent invasion dynamics can provide insight into the underlying mechanisms driving invasions and assist biosecurity agencies with prioritizing areas for proactive surveillance and management.

   United States of America.

   1794–2018.

   Insecta, plant pathogens.

   Using locations of first discovery and county‐level occurrence data for 101 non‐native pests across the contiguous USA, we (a) quantified spatial patterns in discovery points and county‐level species richness with spatial point process models and spatial hotspot analyses, respectively, and (b) identified potential proxies for propagule pressure (e.g., human population density) associated with these observed patterns.

   Discovery points were highly aggregated in space and located in areas with high densities of ports and roads. Although concentrated in the north‐eastern USA, discovery points also occurred farther west and became less aggregated as time progressed. Invasion hotspots were more common in the north‐east. Geographic patterns of discovery points and hotspots varied substantially among pest origins (i.e., global region of pests’ native ranges) and pest feeding guilds. Significant variation in invasion richness was attributed to the patterns of first discovery locations. Data and shapefiles comprising analyses are provided.

   Use of spatial point pattern analyses provided a quantitative characterization of the central role of human activities in establishment of non‐native pests. Moreover, the decreased aggregation of discovery points through time suggests that invasion pathways to certain areas in the USA have either been created or intensified by human activities. Overall, our results suggest that spatio‐temporal variability in the intensity of invasion pathways has resulted in marked geographic patterns of establishment and contributed to current macroscale patterns of pest invasion in the USA.

    

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