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1. Global flows of insect transport and establishment: The role of biogeography, trade and regulations

   https://doi.org/10.1111/ddi.13772  

   Fenn‐Moltu, Gyda ; Ollier, Sébastien ; Bates, Olivia K. ; Liebhold, Andrew M. ; Nahrung, Helen F. ; Pureswaran, Deepa S. ; Yamanaka, Takehiko ; Bertelsmeier, Cleo ( September 2023 , Diversity and Distributions)

   Non‐native species are part of almost every biological community worldwide, yet numbers of species establishments have an uneven global distribution. Asymmetrical exchanges of species between regions are likely influenced by a range of mechanisms, including propagule pressure, native species pools, environmental conditions and biosecurity. While the importance of different mechanisms is likely to vary among invasion stages, those occurring prior to establishment (transport and introduction) are difficult to account for. We used records of unintentional insect introductions to test (1) whether insects from some biogeographic regions are more likely to be successful invaders, (2) whether the intensity of trade flows between regions determines how many species are intercepted and how many successfully establish, and (3) whether the variables driving successful transport and successful establishment differ.

   Canada, mainland USA, Hawaii, Japan, Australia, New Zealand, Great Britain, South Korea, South Africa.

   To disentangle processes occurring during the transport and establishment stages, we analysed border interceptions of 8199 insect species as a proxy for transported species flows, and lists of 2076 established non‐native insect species in eight areas. We investigated the influence of biogeographic variables, socio‐economic variables and biosecurity regulations on the size of species flows between regions.

   During transport, the largest species flows generally originated from the Nearctic, Panamanian and Neotropical regions. Insects native to 8 of 12 biogeographic regions were able to establish, with the largest flows of established species on average coming from the Western Palearctic, Neotropical and Australasian/Oceanian regions. Both the biogeographic region of origin and trade intensity significantly influenced the size of species flows between regions during transport and establishment. The transported species richness increased with Gross National Income in the source country, and decreased with geographic distance. More species were able to establish when introduced within their native biogeographic region.

   Our results suggest that accounting for processes occurring prior to establishment is crucial for understanding invasion asymmetry in insects, and for quantifying regional biosecurity risks.

    

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2. Disturbance or propagule pressure? Unravelling the drivers and mapping the intensity of invasion of free‐ranging dogs across the Atlantic forest hotspot

   https://doi.org/10.1111/ddi.12845  

   Ribeiro, Fernando S. ; Nichols, Elizabeth ; Morato, Ronaldo G. ; Metzger, Jean Paul ; Pardini, Renata ; Santini, ed., Luca ( December 2018 , Diversity and Distributions)

   Identifying the drivers of biological invasions is crucial to predict the risk of invasion across broad spatial scales and to devise strategies to prevent invasion impacts. Here, we explore the relative importance and synergies between two key drivers—propagule pressure and landscape disturbance—in determining the invasion of native forest remnants by dogs, one of the most abundant, widely distributed, and harmful invasive species worldwide.

   Brazilian Atlantic Forest.

   Combining a camera trap dataset (96 sites in forest remnants) and censuses of populations of dogs raised by humans across 12 landscapes (2,830 ha each), we usedN‐mixture models that account for imperfect detection to confront alternative hypotheses of invasion drivers. We then used this empirical evidence to predict the intensity of dog invasion across the Atlantic Forest hotspot.

   Propagule pressure (density of raised dogs, positive effect) and landscape disturbance (forest cover, negative effect) were equally important drivers of dog invasion, presenting additive rather than synergistic effects. Dogs invade forest remnants far from their homes, making the density of raised dogs the key component of propagule pressure (relative to dog spatial distribution). Forest cover was more important than either the length or density of forest edges, suggesting that both reduced area of forested barriers to long‐distance movements and increased proximity of forests to edges facilitate dog access to forests. Across the Atlantic Forest, the combination of high human population density and extensive deforestation makes dog invasion an additional and widespread threat.

   Combined with available maps of priority areas for biodiversity conservation, our spatial prediction of dog invasion can help target areas for integrated management actions. These actions should go beyond measures to control dog populations and encompass the maintenance and restoration of native forests and strategic planning of afforestation through planted forests.

    

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3. Exploring potential establishment of marine rafting species after transoceanic long‐distance dispersal

   https://doi.org/10.1111/geb.12878  

   Simkanin, Christina ; Carlton, James T. ; Steves, Brian ; Fofonoff, Paul ; Nelson, Jocelyn C. ; Clarke Murray, Cathryn ; Ruiz, Gregory M. ; Bates, ed., Amanda ( January 2019 , Global Ecology and Biogeography)

   On 11 March 2011, the Great East Japan Earthquake triggered a massive tsunami that resulted in the largest known rafting event in recorded history. By spring 2012, marine debris began washing ashore along the Pacific coast of the United States and Canada with a wide range of Asian coastal species attached. We used this unique dataset, where the source region, date of dislodgment and landing location are known, to assess the potential for species invasions by transoceanic rafting on marine debris.

   Northeast Pacific from 20 to 60°N.

   Current.

   Forty‐eight invertebrate and algal species recorded on Japanese tsunami marine debris (JTMD).

   We developed maximum entropy (MaxEnt) species distribution models for 48 species recorded on JTMD to predict establishment potential along the Pacific coast from 20 to 60°N. Models were compared within the context of historical marine introductions from Japan to this region to validate the emergence of marine debris as a novel vector for species transfer.

   Overall, 27% (13 species) landed with debris at locations with suitable environmental conditions for establishment and survival, indicating that these species may be able to establish new populations or introduce greater genetic diversity to already established non‐native populations. A further 21 species have an environmental match to areas where tsunami debris likely landed, but was not extensively sampled. Nearly 100 Japanese marine species previously invaded the northeastern Pacific, demonstrating this region’s environmental suitability for rafting Japanese biota. Historical invasions from Japan are highest in California and largely known from bays and harbours.

   Marine debris is a novel and growing vector for non‐native species introduction. By utilizing a unique dataset of JTMD species, our predictive models show capacity for new transoceanic invasions and can focus monitoring priorities to detect successful long‐distance dispersal across the world’s oceans.

    

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4. Global patterns of genomic and phenotypic variation in the invasive harlequin ladybird

   https://doi.org/10.1186/s12915-023-01638-7  

   Li, Hongran ; Peng, Yan ; Wang, Yansong ; Summerhays, Bryce ; Shu, Xiaohan ; Vasquez, Yumary ; Vansant, Hannah ; Grenier, Christy ; Gonzalez, Nicolette ; Kansagra, Khyati ; et al ( December 2023 , BMC Biology)

   The harlequin ladybirdHarmonia axyridis(Coleoptera: Coccinellidae), native to Asia, has been introduced to other major continents where it has caused serious negative impacts on local biodiversity. Though notable advances to understand its invasion success have been made during the past decade, especially with then newer molecular tools, the conclusions reached remain to be confirmed with more advanced genomic analyses and especially using more samples from larger geographical regions across the native range. Furthermore, althoughH. axyridisis one of the best studied invasive insect species with respect to life history traits (often comparing invasive and native populations), the traits responsible for its colonization success in non-native areas warrant more research.

   Our analyses of genome-wide nuclear population structure indicated that an eastern Chinese population could be the source of all non-native populations and revealed several putatively adaptive candidate genomic loci involved in body color variation, visual perception, and hemolymph synthesis. Our estimates of evolutionary history indicate (1) asymmetric migration with varying population sizes across its native and non-native range, (2) a recent admixture between eastern Chinese and American populations in Europe, (3) signatures of a large progressive, historical bottleneck in the common ancestors of both populations and smaller effective sizes of the non-native population, and (4) the southwest origin and subsequent dispersal routes within its native range in China. In addition, we found that while two mitochondrial haplotypes-Hap1 and Hap2 were dominant in the native range, Hap1 was the only dominant haplotype in the non-native range. Our laboratory observations in both China and USA found statistical yet slight differences between Hap1 and Hap2 in some of life history traits.

   Our study onH.axyridisprovides new insights into its invasion processes into other major continents from its native Asian range, reconstructs a geographic range evolution across its native region China, and tentatively suggests that its invasiveness may differ between mitochondrial haplotypes.

    

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5. Traits linked with species invasiveness and community invasibility vary with time, stage and indicator of invasion in a long‐term grassland experiment

   https://doi.org/10.1111/ele.13220  

   Catford, Jane A. ; Smith, Annabel L. ; Wragg, Peter D. ; Clark, Adam T. ; Kosmala, Margaret ; Cavender‐Bares, Jeannine ; Reich, Peter B. ; Tilman, David ; Rejmanek, ed., Marcel ( February 2019 , Ecology Letters)

   Much uncertainty remains about traits linked with successful invasion – the establishment and spread of non‐resident species into existing communities. Using a 20‐year experiment, where 50 non‐resident (but mostly native) grassland plant species were sown into savannah plots, we ask how traits linked with invasion depend on invasion stage (establishment, spread), indicator of invasion success (occupancy, relative abundance), time, environmental conditions, propagule rain, and traits of invaders and invaded communities. Trait data for 164 taxa showed that invader occupancy was primarily associated with traits of invaders, traits of recipient communities, and invader‐community interactions. Invader abundance was more strongly associated with community traits (e.g. proportion legume) and trait differences between invaders and the most similar resident species. Annuals and invaders with high‐specific leaf area were only successful early in stand development, whereas invaders with conservative carbon capture strategies persisted long‐term. Our results indicate that invasion is context‐dependent and long‐term experiments are required to comprehensively understand invasions.

    

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