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1. Native biodiversity collapse in the eastern Mediterranean

   https://doi.org/10.1098/rspb.2020.2469  

   Albano, Paolo G. ; Steger, Jan ; Bošnjak, Marija ; Dunne, Beata ; Guifarro, Zara ; Turapova, Elina ; Hua, Quan ; Kaufman, Darrell S. ; Rilov, Gil ; Zuschin, Martin ( January 2021 , Proceedings of the Royal Society B: Biological Sciences)

   null (Ed.)

   Global warming causes the poleward shift of the trailing edges of marine ectotherm species distributions. In the semi-enclosed Mediterranean Sea, continental masses and oceanographic barriers do not allow natural connectivity with thermophilic species pools: as trailing edges retreat, a net diversity loss occurs. We quantify this loss on the Israeli shelf, among the warmest areas in the Mediterranean, by comparing current native molluscan richness with the historical one obtained from surficial death assemblages. We recorded only 12% and 5% of historically present native species on shallow subtidal soft and hard substrates, respectively. This is the largest climate-driven regional-scale diversity loss in the oceans documented to date. By contrast, assemblages in the intertidal, more tolerant to climatic extremes, and in the cooler mesophotic zone show approximately 50% of the historical native richness. Importantly, approximately 60% of the recorded shallow subtidal native species do not reach reproductive size, making the shallow shelf a demographic sink. We predict that, as climate warms, this native biodiversity collapse will intensify and expand geographically, counteracted only by Indo-Pacific species entering from the Suez Canal. These assemblages, shaped by climate warming and biological invasions, give rise to a ‘novel ecosystem’ whose restoration to historical baselines is not achievable. 

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2. 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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3. Tracking invasions of a destructive defoliator, the gypsy moth (Erebidae: Lymantria dispar ): Population structure, origin of intercepted specimens, and Asian introgression into North America

   https://doi.org/10.1111/eva.12962  

   Wu, Yunke ; Bogdanowicz, Steven M. ; Andres, Jose A. ; Vieira, Kendra A. ; Wang, Baode ; Cossé, Allard ; Pfister, Scott E. ( April 2020 , Evolutionary Applications)

   Genetic data can help elucidate the dynamics of biological invasions, which are fueled by the constant expansion of international trade. The introduction of European gypsy moth (Lymantria dispar dispar) into North America is a classic example of human‐aided invasion that has caused tremendous damage to North American temperate forests. Recently, the even more destructive Asian gypsy moth (mainlyL. d. asiaticaandL. d. japonica) has been intercepted in North America, mostly transported by cargo ships. To track invasion pathways, we developed a diagnostic panel of 60 DNA loci (55 nuclear and 5 mitochondrial) to characterize worldwide genetic differentiation withinL. disparand its sister speciesL. umbrosa. Hierarchical analyses supported strong differentiation and recovered five geographic groups that correspond to (1) North America, (2) Europe plus North Africa and Middle East, (3) the Urals, Central Asia, and Russian Siberia, (4) continental East Asia, and (5) the Japanese islands. Interestingly,L. umbrosawas grouped withL. d. japonica, and the introduced North American population exhibits remarkable distinctiveness from contemporary European counterparts. Each geographic group, except for North America, shows additional lower‐level structures when analyzed individually, which provided the basis for inference of the origin of invasive specimens. Two assignment approaches consistently identified a coastal area of continental East Asia as the major source for Asian invasion during 2014–2015, with Japan being another source. By analyzing simulation and laboratory crosses, we further provided evidence for the occurrence of natural Asian–North American hybrids in the Pacific Northwest, raising concerns for introgression of Asian alleles that may accelerate range expansion of gypsy moth in North America. Our study demonstrates how genetic data contribute to bio‐surveillance of invasive species with results that can inform regulatory management and reduce the frequency of trade‐associated invasions.

    

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4. Whole‐genome resequencing reveals persistence of forest‐associated mammals in Late Pleistocene refugia along North America’s North Pacific Coast

   https://doi.org/10.1111/jbi.14068  

   Colella, Jocelyn P. ; Lan, Tianying ; Talbot, Sandra L. ; Lindqvist, Charlotte ; Cook, Joseph A. ( March 2021 , Journal of Biogeography)

   Numerous glacial refugia have been hypothesized along North America's North Pacific Coast that may have increased divergence of refugial taxa, leading to elevated endemism and subsequently clustered hybrid zones following deglaciation. The locations and community composition of these ice‐free areas remains controversial, but whole‐genome sequences now enable detailed analysis of the demographic and evolutionary histories of refugial taxa. Here, we use genomic data to test spatial and temporal processes of diversification among martens with respect to the Coastal Refugium Hypothesis, to understand the role of climate cycling in shaping diversity across complex landscapes.

   North America and North Pacific Coast archipelagos.

   North American martens (Martes).

   Short‐read whole‐genome resequencing data were generated for 11 martens: fourM. americana, fourM. caurina, two hybrids, and one outgroup (Martes zibellina). Sampling was representative of known genetic clades within New World martens, including sampling within insular and continental hybrid zones and along the North Pacific Coast (five island populations).ADMIXTURE, F‐statistics, andD‐statistics (ABBA‐BABA) were used to identify introgression and infer directionality. Heterozygosity densities, estimated via PSMC, were used to characterize historical demography at and below the species level to infer refugial and colonization processes.

   Forest‐associated Pacific martens (M. caurina) are divided into distinct insular and continental clades consistent with the Coastal Refugium Hypothesis. There was no evidence of introgression on islands that received historical translocations of American pine martens (M. americana), but introgression was detected in two active zones of secondary contact: one insular and one continental. Only early‐generational hybrids were identified across multiple hybrid zones, a pattern consistent with potential genetic swamping ofM. caurinabyM. americana.

   Despite an incomplete fossil record, genomic evidence supports the persistence of forest‐associated martens, likely the insular Pacific marten lineage, along the western edges of the Alexander Archipelago during the Last Glacial Maximum. This discovery informs our understanding of refugial paleoenvironments, critical to interpreting refugial timing, duration, and community composition. Genomic reevaluations of other taxa along North America's North Pacific Coast may yield new and deeper perspectives on the history of refugial forest communities and the role of dynamic climate shifts in shaping high‐latitude diversity across complex insular landscapes.

    

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5. Expanding the invasion footprint: Ventenata dubia and relationships to wildfire, environment, and plant communities in the Blue Mountains of the Inland Northwest, USA

   https://doi.org/10.1111/avsc.12511  

   Tortorelli, Claire M. ; Krawchuk, Meg A. ; Kerns, Becky K. ; Fraser, ed., Lauchlan ( August 2020 , Applied Vegetation Science)

   A recently introduced non‐native annual grass,Ventenata dubia, is challenging previous conceptions of community resistance in forest mosaic communities in the Inland Northwest. However, little is known of the drivers and potential ecological impacts of this rapidly expanding species. Here we (1) identify abiotic and biotic habitat characteristics associated with theV. dubiainvasion and examine how these differ betweenV. dubiaand other problematic non‐native annual grasses,Bromus tectorumandTaeniatherum caput‐medusae; and (2) determine how burning influences relationships betweenV. dubiaand plant community composition and structure to address potential impacts on Inland Northwest forest mosaic communities.

   Blue Mountains of the Inland Northwest, USA.

   We measured environmental and plant community characteristics in 110 recently burned and nearby unburned plots. Plots were stratified to capture a range ofV. dubiacover, elevations, biophysical classes, and fire severities. We investigated relationships betweenV. dubia, wildfire, environmental, and plant community characteristics using non‐metric multidimensional scaling and linear regressions.

   Ventenata dubiawas most abundant in sparsely vegetated, basalt‐derived rocky scablands interspersed throughout the forested landscape. Plant communities most heavily invaded byV. dubiawere largely uninvaded by other non‐native annual grasses.Ventenata dubiawas abundant in both unburned and burned areas, but negative relationships betweenV. dubiacover and community diversity were stronger in burned plots, where keystone sagebrush species were largely absent after fire.

   Ventenata dubiais expanding the overall invasion footprint into previously uninvaded communities. Burning may exacerbate negative relationships betweenV. dubiaand species richness, evenness, and functional diversity, including in communities that historically rarely burned. Understanding the drivers and impacts of theV. dubiainvasion and recognizing how these differ from other annual grass invasions may provide insight into mechanisms of community invasibility, grass‐fire feedbacks, and aid the development of species‐specific management plans.

    

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