Related Native Species Research Articles

Landscape change and alien invasions drive shifts in native lady beetle communities over a century.

Understanding causes of insect population declines is essential for the development of successful conservation plans, but data limitations restrict assessment across spatial and temporal scales. Museum records represent a source of historical data that can be leveraged to investigate temporal trends in insect communities. Native lady beetle decline has been attributed to competition with established alien species and landscape change, but the relative importance of these drivers is difficult to measure with short-term field-based studies. We assessed distribution patterns for native lady beetles over 12 decades using museum records, and evaluated the relative importance of alien species and landscape change as factors contributing to changes in communities. We compiled occurrence records for 28 lady beetle species collected in Ohio, USA, from 1900 to 2018. Taxonomic beta-diversity was used to evaluate changes in lady beetle community composition over time. To evaluate the relative influence of temporal, spatial, landscape, and community factors on the captures of native species, we constructed negative binomial generalized additive models. We report evidence of declines in captures for several native species. Importantly, the timing, severity, and drivers of these documented declines were species-specific. Land cover change was associated with declines in captures, particularly for Coccinella novemnotata which declined prior to the arrival of alien species. Following the establishment and spread of alien lady beetles, processes of species loss/gain and turnover shifted communities toward the dominance of a few alien species beginning in the 1980s. Because factors associated with declines in captures were highly species-specific, this emphasizes that mechanisms driving population losses cannot be generalized even among closely related native species. These findings also indicate the importance of museum holdings and the analysis of species-level data when studying temporal trends in insect populations.

Thin lines between native and invasive aquatic plants are common, posing challenges for response efforts

Abstract Lines separating native and invasive plant species can be thin due to close relatedness, obscured by cryptic invasions, or breached by hybridization. Past work suggests these phenomena are especially prevalent in aquatic systems. This could arise from strong filters imposed by aquatic environments magnifying the importance of ‘preadaptation’—non‐native species succeeding where closely related native species occur due to shared traits. If so, there should be stronger signals of preadaptation in aquatic than terrestrial plant invasions, with implications for management. I tested for stronger influence of preadaptation in aquatic than terrestrial invasions by comparing relatedness of invasive and native species in aquatic versus terrestrial flora of the Midwestern USA using herbarium records and taxonomic and phylogenetic analyses. I predicted that aquatic species would constitute an evolutionarily distinct subset of plants; aquatic invaders would be more closely related, taxonomically and phylogenetically, to native aquatic plants than terrestrial invaders are to their native counterparts; and aquatic invaders from the Midwest's primary donor region (the Palearctic) would be more closely related to Midwestern species than are Palearctic aquatic plants that are not invasive in the Midwest. Findings supported the evolutionary legacy of adaptation to aquatic environments being reflected in thin lines separating invasive and native aquatic plants. Aquatic species constituted an evolutionarily distinct subset of plants, and invasive aquatic plants were more closely related to native aquatic plants (taxonomically and phylogenetically) than terrestrial invaders were to terrestrial native species. Additionally, aquatic plants of the Palearctic that are invasive in the Midwest were more closely related to Midwestern natives (phylogenetically, but not taxonomically) than were their non‐invasive counterparts, reinforcing the role of preadaptation. Synthesis and applications: Thin lines separating native from invasive aquatic plants pose challenges for response efforts. For resource managers, the prevalence of cryptic invasions requires dedicated, robust approaches to surveillance. For outreach, finer distinctions between native and invasive necessitate nuanced approaches to communication and education. And when control is needed, it should be implemented cautiously to minimize nontarget impacts to close native relatives, but thoroughly enough to prevent native relatives being displaced by competition and/or introgression.

Germination niche of co-occurring threatened native and alien species: a case study in Lindernia procumbens and L. dubia

Plant invasions have a negative impact on biodiversity and lead to species loss. Although studies on traits promoting invasiveness have been largely developed, comparative studies on germination traits of closely related native versus alien invasive species, which also take into account threatened species, are lacking. We analysed the germination requirements of two congeneric Lindernia species inhabiting paddy field in Northern Italy. Germination tests were conducted exposing seeds of both species across a broad range of temperature and conditions (i.e., cold-wet stratification, dark condition, alternate temperature, gibberellic acid). The invasive L. dubia showed higher and faster germination, occurring over a broader range of temperatures compared to the native threatened L. procumbens, along with a lighter non-deep physiological dormancy. These results show a competitive advantage of the alien species already in the early stages of plant regeneration and provide a comprehensive overview of the germination requirements, necessary for the development of future conservation and management plans.

Comparative study of the gut microbial community structure of Spodoptera frugiperda and Spodoptera literal (Lepidoptera).

Spodoptera frugiperda, the fall armyworm is a destructive invasive pest, and S. litura the tobacco cutworm, is a native species closely related to S. frugiperda. The gut microbiota plays a vital role in insect growth, development, metabolism and immune system. Research on the competition between invasive species and closely related native species has focused on differences in the adaptability of insects to the environment. Little is known about gut symbiotic microbe composition and its role in influencing competitive differences between these two insects. We used a culture-independent approach targeting the 16S rRNA gene of gut bacteria of 5th instar larvae of S. frugiperda and S. litura. Larvae were reared continuously on maize leaves for five generations. We analyzed the composition, abundance, diversity, and metabolic function of gut microbiomes of S. frugiperda and S. litura larvae. Firmicutes, Proteobacteria, and Bacteroidetes were the dominant bacterial phyla in both species. Enterococcus, ZOR0006, Escherichia, Bacteroides, and Lactobacillus were the genera with the highest abundance in S. frugiperda. Enterococcus, Erysipelatoclostridium, ZOR0006, Enterobacter, and Bacteroides had the highest abundance in S.litura. According to α-diversity analysis, the gut bacterial diversity of S. frugiperda was significantly higher than that of S.litura. KEGG analysis showed 15 significant differences in metabolic pathways between S. frugiperda and S. litura gut bacteria, including transcription, cell growth and death, excretory system and circulatory system pathways. In the same habitat, the larvae of S. frugiperda and S. litura showed significant differences in gut bacterial diversity and community composition. Regarding the composition and function of gut bacteria, the invasive species S. frugiperda may have a competitive advantage over S. litura. This study provides a foundation for developing control strategies for S. frugiperda and S. litura.

The non-native Quercus rubra does not substitute the native Quercus robur and Q. petraea as substrate for epiphytic lichens and bryophytes

Climate change will cause alterations in tree species ranges. Non-native tree species are likely to be increasingly used in production forests, due to their often better adaptation to a warmer climate and their lower susceptibility to pests and pathogens. Trees form an important habitat for numerous species, many of which are more or less specialised regarding tree species. Thus, the tree-associated flora and fauna may be heavily impacted if non-native trees replace native ones. Risk assessments from the introduction of non-native trees must rest on a solid knowledge base, including insights into the potential of such trees to function as biodiversity substitutes, i.e. to host similar biodiversity as closely related native tree species. In a study in temperate Sweden, we inventoried epiphytic lichens and bryophytes on ten random trees in each of 28 stands (14 stands of North American red oak Quercus rubra and 14 stands of native oak Q. robur/petraea), to compare species richness and composition. Overall, 101 lichen taxa and 35 bryophyte taxa were identified, and we found a generally higher diversity for native oak. The regional species richness (gamma diversity) for both lichens and bryophytes was higher in native oak than in red oak, and the lichen species richness at stand level (alpha diversity) was nearly significantly higher. Lichen composition differed between the two oak species, while there was no difference for bryophytes. More lichens were strongly associated with native oak than red oak, while most bryophyte species were generalists with no specific preference for either oak taxa. Bark structure was an important explanatory variable separating the lichen epiphytes, with species preferring smooth bark largely confined to red oak. In conclusion, our study suggests that substituting native oak with red oak could have adverse consequences for epiphytic lichen populations associated with native oak, resulting in a decline of several species. However, certain lichen and bryophyte species were exclusively found on Q. rubra, implying that incorporating a proportion of red oak stands in southern Swedish landscapes may enhance diversity. Further research is needed to explore the overlap between species associated with Q. rubra and other deciduous tree species that possess similar smooth bark. Our findings indicate that red oak may not be an appropriate alternative host tree for epiphytic lichens typically found on native oak, while the implications for bryophytes remain less clear.

Germination ecology and seedling growth of invasive Ageratum species and allied native Adenostemma lavenia

AbstractThe success of invasive plants can be better understood by comparing their traits with closely related native species. This study compared germination ecology and seedling growth of invasive Ageratum houstonianum and Ageratum conyzoides with co‐occurring and allied native Adenostemma lavenia. Seeds were germinated under a different light (12 h photoperiod/complete dark), temperatures (low: 25°C/15°C day/night, and high: 30°C/20°C), and different levels of water stress (−0.1, −0.25, −0.5, −0.75, and −1 MPa). Seedlings were grown to determine biomass allocation, relative growth rate (RGR), plant height, and number of leaves. The seed mass and size of native A. lavenia were higher than those of invasive species. Seeds of all species were positively photoblastic. At low temperature and in all levels of water stress, all measured parameters except mean germination time were the highest in A. houstonianum. However, at high temperature, there was no significant difference in germination percentage between A. houstonianum and A. lavenia. No germination of A. conyzoides and A. lavenia was recorded beyond −0.5 MPa water potential, but seeds of A. houstonianum germinated up to −0.75 MPa. A. houstonianum had higher root mass fraction, root‐to‐shoot ratio, and number of leaves than the other two species. Stem mass fraction and the height of seedling were highest in A. conyzoides. The RGR was 1.6 times higher in invasive Ageratum species than the native species; it was slightly higher in A. houstonianum than in A. conyzoides. Overall, the results suggest that germination traits and seedling growth performance can be used as predictors of a species' invasiveness.

Cross-mating between the alien bumblebee Bombus terrestris and two native Japanese bumblebees, B. hypocrita sapporensis and B. cryptarum florilegus, in the Nemuro Peninsula, Japan

The rapid naturalization of Bombus terrestris across the Nemuro Peninsula has led to a decline in two closely related native Japanese species, namely Bombus hypocrita sapporensis and Bombus cryptarum florilegus, both belonging to the common subgenus Bombus. Although it is widely believed that cross-mating of native and non-native species is influenced by the common male sex pheromone in this region, no study has been conducted to substantiate this claim. Thus, we investigated the cross-activities of male sex pheromones between native and non-native bumblebees, as well as the frequencies of cross-mating, using chemical and DNA assays. Our gas chromatography–electroantennographic detector analyses and behavioral tests revealed the presence of sex pheromonal cross-activities between B. terrestris and the two Japanese bumblebees species. Furthermore, DNA analyses revealed the occurrence of cross-mating between native and non-native species in the Nemuro Peninsula. Overall, these results indicate the immediate need for conservation measures to safeguard Japanese bumblebee populations in the Nemuro Peninsula.

The Plant Invader Alternanthera philoxeroides Benefits from Clonal Integration More than Its Native Co-Genus in Response to Patch Contrast.

Different connected parts of clonal plants often grow in different patches and the resource contrast between patches has an important effect on the material transfer between the connected ramets. However, it is unclear whether the effect of clonal integration differs between the invasive clonal plant and the related native species in response to patch contrast. To explore this, we grew the clonal fragment pairs of plant invader Alternanthera philoxeroides and its co-genus native species A. sessilis under high contrast, low contrast, and no contrast (control) nutrient patch environments, respectively, and with stolon connections either severed or kept intact. The results showed that, at the ramet level, clonal integration (stolon connection) significantly improved the growth of apical ramets of both species, and such positive effects were significantly greater in A. philoxeroides than in A. sessilis. Moreover, clonal integration greatly increased the chlorophyll content index of apical ramets and the growth of basal ramets in A. philoxeroides but not in A. sessilis under low and high contrast. At the whole fragment level, the benefits of clonal integration increased with increasing patch contrast, and such a positive effect was more pronounced in A. philoxeroides than in A. sessilis. This study demonstrated that A. philoxeroides possesses a stronger ability of clonal integration than A. sessilis, especially in patchy environments with a higher degree of heterogeneity, suggesting that clonal integration may give some invasive clonal plants a competitive advantage over native species, thus facilitating their invasion in patchy habitats.

Translocation precipitates natural hybridisation and pervasive introgression between marine gastropods with divergent developmental modes

Assisted colonisation, the introduction of species beyond their historical range, is increasingly necessary for conserving species. However, empirical evidence of the long-term genetic outcomes of assisted colonisation is grossly lacking. A risk associated with moving species beyond their native range is the possibility of interspecific hybridisation with a closely related species, potentially resulting in outbreeding depression or the genetic swamping of a parental species. Here, we use a combination of genome-wide Single Nucleotide Polymorphism (SNP) markers and mitochondrial DNA sequencing to determine the long-term genetic consequences of introducing the intertidal periwinkle Bembicium vittatum (a direct developer) beyond its native range and into the native range of its congener Bembicium auratum (a species with planktotrophic larval dispersal). We found novel evidence of natural, multigenerational hybridisation between marine invertebrates with different modes of development. Intriguingly, introgression was highly asymmetrical initially, but became more evenly bidirectional as the population became more admixed. There was a significant decline in the frequency of alleles from the introduced B. vittatum over time, providing evidence of genetic swamping. The present study also provides potential evidence of outbreeding depression, in the form of cytonuclear incompatibilities, leading to the observed pattern of asymmetrical introgression. This study reveals the potential for unexpected mixing between species when reproductive barriers are not well understood, resulting in failure of pure B. vittatum to persist at the translocation site, a major concern associated with assisted colonisation. Without long-term genetic monitoring interspecific hybridisation between B. vittatum and B. auratum would have gone undetected, highlighting the importance of long-term monitoring to detect unintentional negative consequences of conservation translocations. Successful assisted colonisation requires an understanding of the potential for interspecific hybridisation between the threatened species and closely related native species, to reduce the risk of adverse outcomes.

Evidence of biotic resistance to exotic plant invasion in degraded Bornean forests

AbstractIntact tropical forests are generally considered to be resistant to invasions by exotic species, although the shrub Clidemia hirta (Melastomataceae) is highly invasive in tropical forests outside its native range. Release from natural enemies (e.g., herbivores and pathogens) contributes to C. hirta invasion success where native melastomes are absent, and here we examine the role of enemies when C. hirta co‐occurs with native Melastomataceae species and associated herbivores and pathogens. We study 21 forest sites within agricultural landscapes in Sabah, Malaysian Borneo, recording herbivory rates in C. hirta and related native Melastoma spp. plants along two 100‐m transects per site that varied in canopy cover. Overall, we found evidence of enemy release; C. hirta had significantly lower herbivory (median occurrence of herbivory per plant = 79% of leaves per plant; median intensity of herbivory per leaf = 6% of leaf area) than native melastomes (93% and 20%, respectively). Herbivory on C. hirta increased when closer to native Melastoma plants with high herbivory damage, and in more shaded locations, and was associated with fewer reproductive organs on C. hirta. This suggests host‐sharing by specialist Melastomataceae herbivores is occurring and may explain why invasion success of C. hirta is lower on Borneo than at locations without related native species present. Thus, natural enemy populations may provide a “biological control service” to suppress invasions of exotic species (i.e., biotic resistance). However, lower herbivory pressures in more open canopy locations may make highly degraded forests within these landscapes more susceptible to invasion.Abstract in Malay is available with online material.

Torymus sinensis against the invasive chestnut gall wasp: Evaluating the physiological host range and hybridization risks of a classical biological control agent

BackgroundA common strategy to limit the negative impact of biological invasions is biological control through the release of specialized alien natural enemies. However, biological control plans are not without risks, which include parasitism of native hosts and hybridization with related native species, particularly those that are potential natural enemies of the invasive species. Here, we evaluate these potential risks resulting from the introduction of the parasitoid wasp Torymus sinensis (Hymenoptera: Torymidae) in Europe to control the invasive Asian chestnut gall wasp Dryocosmus kuriphilus (Hymenoptera: Cynipidae). ResultsWe found that, under laboratory conditions, the physiological host range of T. sinensis includes several native non-target species of Cynipidae, with oviposition observed on the galls of 8 of the 11 species tested. However, physiological host range of T. sinensis appears to be limited under field conditions, as we observed only one parasitized gall of Andricus curvator in the field. Regarding hybridization, inter-species mating between T. sinensis and its phylogenetically closest native Torymus species was not observed in the laboratory. Moreover, discordance between nuclear (ITS2) and mitochondrial (coxI) data does not support the presence of genetic introgression, suggesting that hybridization between T. sinensis and native Torymus species does not occur. In addition, we cite and discuss the unexpected presence of one individual of the related alien species Torymus beneficus in Spain. ConclusionOur results suggest that T. sinensis may negatively impact several non-target species, highlighting the need for careful monitoring of the extent of such undesired behaviour and its effects on the native fauna.

Stomatal Study of Introduced Species, Ligustrum lucidum Aiton (Oleaceae), in Coastal Areas of Japan

Alien, introduced, and non-native species expand their distribution through the development of various transportation networks. In Japan, Ligustrum lucidum Aiton (Oleaceae) was introduced in the mid-1800s for use as roadside trees, but has escaped from the planting area and spread everywhere. This species also invades coastal areas and has adapted to develop its characteristic features under various stress conditions. To clarify the adaptive features of L. lucidum in coastal areas, we conducted morphological and anatomical analyses. We found that the stomatal size of L. lucidum was smaller in the coastal populations than in inland populations, which is similar to the coastal adaptation pattern of L. japonicum Thunb., a closely related native species. Our results suggest that strong selective pressure on coastal area conditions could force their leaves to avoid excessive transpiration, and such an adaptation pattern of L. lucidum could expand its distribution to various coastal areas.

Testing enemy release of non‐native plants across time and space using herbarium specimens in Norway

Abstract The enemy release hypothesis predicts that invasive plant success is in part due to the absence of natural enemies in the invaded range. However, few studies have assessed how enemy release may vary over time or space. Norway has seen a large increase in non‐native plant species over the past few decades. We used historical herbarium records to test whether 10 non‐native plant species in Norway have suffered less from natural enemies (foliar herbivores) at different latitudes and over the past 195 years, compared to closely related (congeneric) native species. We analysed over 2200 specimens over 26 species. Chewing herbivory was lower at higher latitudes for both non‐native and native species. However, there was no evidence of change over time in overall chewing herbivory for either native or non‐native species on average. Chewing herbivory of native and non‐native species differed within the genera Centaurea, Epilobium and Salix across latitudes, and in the genera Acer, Barbarea, Campanula and Epilobium across time. Synthesis: Our results suggest that enemy release is unlikely to facilitate these non‐native plants in Norway since herbivory levels are similar between both non‐native and native plant species. Herbivory of these non‐native plants did not change over time, suggesting that they were quickly recognized as food sources by native herbivores. Lower levels of herbivory at higher latitudes suggest that herbivory is unlikely to limit non‐native plants further north and that herbivory is likely to increase at higher latitudes as the climate warms.

Emerging pattern of arthropod assemblages, biomass and damage on native and non-native plant species

Assemblages of arthropod on non-native plants are thought to be an important factor contributing to the success of non-native plants. It is hypothesized that is there a difference in the arthropod abundance, biomass and damage between native and non-native plants species. The study investigates arthropods abundance, richness, trophic guilds, arthropod biomass and damage on naturally occurring dominant monocultures of taxonomically close related native ( Plectranthus mollis- Lamiaceae) and non-native ( Hyptis suaveolens- Lamiaceae ) plant species and taxonomically distant native ( Justicia adhatoda- Acanthaceae) and non-native ( Lantana camara- Verbenaceae) plant species across five sites in India. A total of 2,697 arthropods were estimated belonging to 14 taxonomic orders. It was interesting to observe that average arthropod abundance per plant among native and non-native plant species did not differ. Principal component analysis exhibited that insect orders separate out according to their presence and abundance on plant species. Arthropod biomass and damage caused by herbivores on selected native and non-natives plant species was also not significantly different. Predator abundance was high on non-native H. suaveolens than native P. mollis indicating the potential attribute of plant relatedness and role of arthropod trophic guilds assemblages on native and non-native studies. Plant relatedness and arthropod trophic guilds emerged as a key component determining arthropod assemblages on native and non-native plant species. The emerging pattern of arthropod in non-native dominated environments will narrow the gap for habitat restoration.

Genomic Evidence for Rare Hybridization and Large Demographic Changes in the Evolutionary Histories of Four North American Dove Species.

Simple SummaryRange expansions of invasive species continue to increase due to the direct or indirect influences of humans on global habitats. Understanding how these introductions and invasions increase the potential for interaction and hybridization between colonists and closely related native species is therefore increasingly important. We examine the evolutionary histories and signatures of hybridization among introduced feral Rock Pigeon and Eurasian Collared-Dove and native White-winged and Mourning doves in southwestern North America. Analyzing thousands of genomic markers, we find little evidence that hybridization has been extensive in their evolutionary histories or today. Despite this, evidence from multiple population genetics analyses supports the presence of six putative contemporary late-stage hybrids among the 182 sampled individuals. These putative hybrids all involve the most populous species, the Mourning Dove. We discuss the importance of using multiple marker types when attempting to infer complex evolutionary histories and propose important considerations when analyzing populations that were recently established or of domestic origins.Introductions and invasions provide opportunities for interaction and hybridization between colonists and closely related native species. We investigate this phenomenon using the mitochondrial DNA COI and 81,416 base-pairs of overlapping nuclear variation to examine the evolutionary histories and signatures of hybridization among introduced feral Rock Pigeon and Eurasian Collared-Dove and native White-winged and Mourning doves in southwestern North America. First, we report all four species to be highly divergent across loci (overall pair-wise species ΦST range = 0.17–0.70) and provide little evidence for gene flow at evolutionary timescales. Despite this, evidence from multiple population genetics analyses supports the presence of six putative contemporary late-stage hybrids among the 182 sampled individuals. These putative hybrids contain various ancestry combinations, but all involve the most populous species, the Mourning Dove. Next, we use a novel method to reconstruct demographic changes through time using partial genome sequence data. We identify recent, species-specific fluctuations in population size that are likely associated with changing environments since the Miocene and suggest that these fluctuations have influenced the genetic diversity of each dove species in ways that may impact their future persistence. Finally, we discuss the importance of using multiple marker types when attempting to infer complex evolutionary histories and propose important considerations when analyzing populations that were recently established or of domestic origins.

Shifts in leaf herbivory stress and defense strategies of endangered tree species after 20–35 years of ex-situ conservation

Ex-situ conservation, the transplanting of individuals outside of their natural range, can dramatically alter biotic interactions among species. Here, we explored the shifts in the herbivory pressure and defense strategies of ex-situ populations of five endangered tree species (Pterostyrax psilophyllus, Davidia involucrata, Dipteronia sinensis, Tapiscia sinensis, and Tetracentron sinense) after 20–35 years since translocation. All species were not native to the ex-situ site and only P. psilophyllus had a closely related native species (Pterostyrax corymbosus). We compared the leaf damage type, herbivory rate, and chemistry (total phenols, tannins, N, and P) of each species, and assessed the relationship between the herbivory rate and leaf chemistry between the ex-situ and wild populations. Excluding P. psilophyllus, all species in the ex-situ populations showed changes in the type of leaf damage and lower overall herbivory rates. Ex-situ populations of P. psilophyllus showed reduced total phenol, N, and P levels, while the other four species showed decreased total phenol and tannin levels, or increased N and P levels. The herbivory rate was positively correlated with the N and P levels in wild populations, and negatively correlated with the total phenol content in ex-situ populations. These differences reflect the reduced herbivory pressure, decreased defense ability, and shift in defense strategy of ex-situ populations. We showed that prolonged exposure to the ex-situ environment led to the maladaptation of these endangered plant species to herbivory pressure in the natural environment, and that these shifts should be considered in ex-situ conservation and reintroduction strategies.

Two songbird species show subordinate responses to simulated territorial intrusions of an exotic competitor

Interspecific competition is rarely assessed between exotic and distantly related native species, although these can compete for some ecological resources. Here, we assessed the occurrence of interspecific aggression resulting from direct competition between two European native songbird species (henceforth focal species), the robin Erithacus rubecula and the blackcap Sylvia atricapilla, which are potential competitors for feeding resources and behaviourally subordinate to the exotic red-billed leiothrix Leiothrix lutea. In central Portugal, this exotic species lives in sympatry with robins and blackcaps at least since 2007. We used interactive playbacks to measure the behavioural response of blackcaps and robins towards intrusions by leiothrix and a submissive, native competitor—great tit Parus major. The singing behaviour of both focal species was affected by leiothrix playback. Robins exhibited a longer latency to sing, and both species avoided singing near the loudspeaker after leiothrix playback compared with great tit playback, which generally suggests a subordinate behaviour. Regarding changes in song parameters during the playbacks, only the peak frequency of blackcaps was affected by the playback. We discuss different possibilities for the origin of such submissive behaviour in native species.

Assessing the risks of non-target feeding by the accidentally introduced ragweed leaf beetle, Ophraella communa, to native European plant species

In 2013, the North American oligophagous leaf beetle, Ophraella communa LeSage (Coleoptera: Chrysomelidae), was found in Europe for the first time. Recent studies in Northern Italy and Southern Switzerland record extensive defoliation by O. communa on its preferred host, common ragweed, Ambrosia artemisiifolia L. (Asteraceae, Tribe Heliantheae), and reductions in its flowering and seeding. In some regions in Northern Italy, this has reportedly led to a > 80% depletion in airborne A. artemisiifolia pollen concentrations. The potential for non-target damage by O. communa to closely related native European plant species was previously unknown. During extensive field surveys covering 18 populations of nine potential non-target species, we found adult O. communa on a single plant individual. In a common garden field experiment in Northern Italy in an area with high O. communa densities, leaf damage was highest on two other Asteraceae species, Dittrichia graveolens (L.) Greuter and Pentanema helveticum (Weber) D.Gut.Larr. (both in the Tribe Inuleae). While adult feeding was observed on most of the test plant species, only D. graveolens, which has recently extended its range and is now an invasive species in Western Europe, sustained all life stages of O. communa in the common garden and in laboratory experiments. We found no evidence of substantial non-target effects by O. communa that could potentially threaten populations of European native plant species that are taxonomically closely related to ragweed.

Community-level interactions between plants and soil biota during range expansion.

Plant species that expand their range in response to current climate change will encounter soil communities that may hinder, allow or even facilitate plant performance. It has been shown repeatedly for plant species originating from other continents that these plants are less hampered by soil communities from the new than from the original range. However, information about the interactions between intra‐continental range expanders and soil communities is sparse, especially at community level.Here we used a plant–soil feedback experiment approach to examine if the interactions between range expanders and soil communities change during range expansion. We grew communities of range‐expanding and native plant species with soil communities originating from the original and new range of range expanders. In these conditioned soils, we determined the composition of fungi and bacteria by high‐throughput amplicon sequencing of the ITS region and the 16S rRNA gene respectively. Nematode community composition was determined by microscopy‐based morphological identification. Then we tested how these soil communities influence the growth of subsequent communities of range expanders and natives.We found that after the conditioning phase soil bacterial, fungal and nematode communities differed by origin and by conditioning plant communities. Despite differences in bacterial, fungal and nematode communities between original and new range, soil origin did not influence the biomass production of plant communities. Both native and range expanding plant communities produced most above‐ground biomass in soils that were conditioned by plant communities distantly related to them. Synthesis. Communities of range‐expanding plant species shape specific soil communities in both original and new range soil. Plant–soil interactions of range expanders in communities can be similar to the ones of their closely related native plant species.

Comparison of susceptibility to a toxic alien toad (Bufo japonicus formosus) between predators in its native and invaded ranges

Abstract To manage biological invasions effectively, the impacts of alien species on the demography and traits of native species must be known, but determining those impacts can be challenging. We used a comparative approach to gain insight into the impacts that an alien toad (Bufo japonicus formosus) might have on native Japanese predatory amphibians. We compared the susceptibility of native predator species to alien toad toxins in the alien‐invaded range and the susceptibility of closely related native predator species to the toxins in the alien toad's native range to investigate the impacts of an alien on a native species. Bufo japonicus formosus is native to Honshu, but was recently introduced to Hokkaido and Sado. In laboratory experiments, we compared individual mortality of predators exposed to a toad hatchling between novel predators on the toad‐invaded islands and ecologically similar congeneric or conspecific species on Honshu, where the toad is native. We also compared (1) the percentage of individuals that consumed a toad hatchling and (2) toxin resistance (i.e. survival and growth of individuals after toad consumption) between these two groups of predators, as mechanistic components behind the susceptibility of the predators to the toxic prey. The mortality of Rana pirica from all populations after consumption of a toad hatchling was almost 100%, and that of Hynobius retardatus ranged from 14 to 90%, depending on the population. In contrast, the mortality of Rana ornativentris and Hynobius nigrescens was near 0% regardless of population. These differences between congeneric predators were mostly due to differences in their toxin resistance. These results suggest that the alien toad is a potential threat to the novel amphibian predators on Hokkaido, although they also imply that the novel predators on Hokkaido have the potential to develop toxin resistance through adaptive evolution. However, this counteradaptation may have a higher chance of evolving in H. retardatus than in R. pirica because of differences in their genetic backgrounds.