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Data from: Naturalized plants decrease diet similarity between an invasive bird and its most similar native species

Although invasive animals can compete with native species for resources, detrimental competition for food is seldom reported in the avian invasions literature. In temperate climates, food limitation and energetic stress are higher during winter and, thus, winter diets might reveal competition that is not apparent during the rest of the year. We compared autumn and winter diets of the invasive common waxbill (Estrilda astrild) in northwest Iberia, and of the native bird most similar to it in foraging behaviour, the European serin (Serinus serinus). Both species forage for seeds in open habitats, mostly in or around agricultural areas. We found that food preferences of the two species were substantially different when foraging on the same agricultural landscape. Contrary to the prediction that food scarcity in winter would make diets more similar, the diets of waxbills and serins diverged in winter, indicating low potential for detrimental interspecific competition. Differences in diet were in part due to foraging on non-native plants. Non-native seeds represented a large part of the waxbill diet in autumn (a non-native grass), and a small part of serin's (a non-native forb), substantially decreasing their diet similarity. Our results are consistent with the view that waxbills are using vacant niches in human-modified habitats, in this case involving non-crop plants associated with agricultural practices (e.g. irrigation, tillage, harvest) that are underexploited by the native fauna. Understanding which invasive animals fill those vacant niches and, thus, may interfere minimally with native faunas, helps to prioritize conservation actions.

Data from: The thermal dependency of locomotor performance evolves rapidly within an invasive species

Biological invasions can stimulate rapid shifts in organismal performance, via both plasticity and adaptation. We can distinguish between these two proximate mechanisms by rearing offspring from populations under identical conditions, and measuring their locomotor abilities in standardized trials. We collected adult cane toads (Rhinella marina) from invasive populations that inhabit regions of Australia with different climatic conditions. We bred those toads, and raised their offspring under common-garden conditions before testing their locomotor performance. At high (but not low) temperatures, offspring of individuals from a hotter location (northwestern Australia) outperformed offspring of conspecifics from a cooler location (northeastern Australia). This disparity indicates that, within less than 100 years, thermal performance in cane toads has adapted to the novel abiotic challenges that cane toads have encountered during their invasion of tropical Australia.

opencc-zeroDec 2014View details →

Data from: Consequences of seed origin and biological invasion for early establishment of a North American grass species

Local, wild-collected seeds of native plants are recommended for use in ecological restoration to maintain patterns of adaptive variation. However, some environments are so drastically altered by exotic, invasive weeds that original environmental conditions may no longer exist. Under these circumstances, cultivated varieties selected for improved germination and vigor may have a competitive advantage at highly disturbed sites. This study investigated differences in early establishment and seedling performance between wild and cultivated seed sources of the native grass, Poa secunda, both with and without competition from the invasive exotic grass, Bromus tectorum. We measured seedling survival and above-ground biomass at two experimental sites in western Montana, and found that the source of seeds selected for restoration can influence establishment at the restoration site. Cultivars had an overall advantage when compared with local genotypes, supporting evidence of greater vigor among cultivated varieties of native species. This advantage, however, declined rapidly in the presence of B. tectorum and most accessions were not significantly different for growth and survival in competition plots. Only one cultivar had a consistent advantage despite a strong decline in its performance when competing with invasive plants. As a result, cultivated varieties did not meet expectations for greater establishment and persistence relative to local genotypes in the presence of invasive, exotic species. We recommend the use of representative local or regional wild seed sources in restoration to minimize commercial selection, and a mix of individual accessions (wild, or cultivated when necessary) in highly invaded settings to capture vigorous genotypes and increase the odds native plants will establish at restoration sites.

opencc-zeroDec 2016View details →

Data from: A prioritised list of invasive alien species to assist the effective implementation of EU legislation

1. Effective prevention and control of invasive species generally relies on a comprehensive, coherent and representative list of species that enables resources to be used optimally. European Union (EU) Regulation 1143/2014 on invasive alien species (IAS) aims to control or eradicate priority species, and to manage pathways to prevent the introduction and establishment of new IAS; it applies to species considered of Union concern and subject to formal risk assessment. So far, 49 species have been listed but the criteria for selecting species for risk assessment have not been disclosed and were probably unsystematic. 2. We developed a simple method to systematically rank invasive alien species according to their maximum potential threat to biodiversity in the EU. We identified 1323 species as potential candidates for listing, and evaluated them against their invasion stages and reported impacts, using information from databases and scientific literature. 3. 900 species fitted the criteria for listing according to IAS Regulation. We prioritised 207 species for urgent risk assessment, 59 by 2018 and 148 by 2020, based on their potential to permanently damage native species or ecosystems; another 336 species were identified for a second phase (by 2025), to prevent or reverse their profound impacts on biodiversity; and a further 357 species for assessment by 2030. 4. Policy implications. We propose a systematic, proactive approach to selecting and prioritising invasive alien species for risk assessment to assist European Union policy implementation. We assess an unprecedented number of species with potential to harm EU biodiversity using simple methodology that we developed, and recommend which species should be considered for risk assessment in a ranked order of priority along the timeline 2018-2030, based on their maximum reported impact and their invasion history in Europe.

opencc-zeroDec 2015View details →

Data from: Climate, invasive species and land use drive population dynamics of a cold-water specialist

Climate change is an additional stressor in a complex suite of threats facing freshwater biodiversity, particularly for cold-water fishes. Research addressing the consequences of climate change on cold-water fish has generally focused on temperature limits defining spatial distributions, largely ignoring how climatic variation influences population dynamics in the context of other existing stressors. We used long-term data from 92 populations of bull trout Salvelinus confluentus – one of North America's most cold-adapted fishes – to quantify additive and interactive effects of climate, invasive species and land use on population dynamics (abundance, variability and growth rate). Populations were generally depressed, more variable and declining where spawning and rearing stream habitat was limited, invasive species and land use were prevalent and stream temperatures were highest. Increasing stream temperature acted additively and independently, whereas land use and invasive species had additive and interactive effects (i.e. the impact of one stressor depended on exposure to the other stressor). Most (58%–78%) of the explained variation in population dynamics was attributed to the presence of invasive species, differences in life history and management actions in foraging habitats in rivers, lakes and reservoirs. Although invasive fishes had strong negative effects on populations in foraging habitats, proactive control programmes appeared to effectively temper their negative impact. Synthesis and applications. Long-term demographic data emphasize that climate warming will exacerbate imperilment of cold-water specialists like bull trout, yet other stressors – especially invasive fishes – are immediate threats that can be addressed by proactive management actions. Therefore, climate-adaptation strategies for freshwater biodiversity should consider existing abiotic and biotic stressors, some of which provide potential and realized opportunity for conservation of freshwater biodiversity in a warming world.

opencc-zeroDec 2016View details →

Data from: Environmental DNA detection of rare and invasive fish species in two Great Lakes tributaries

The extraction and characterization of DNA from aquatic environmental samples offers an alternative, non-invasive approach for the detection of rare species. Environmental DNA, coupled with PCR and next-generation sequencing ("metabarcoding"), has proven to be very sensitive for the detection of rare aquatic species. Our study used a custom designed group-specific primer set and next-generation sequencing for the detection of three species at risk; (Eastern Sand Darter, Ammocrypta pellucida; Northern Madtom, Noturus stigmosus; and Silver Shiner, Notropis photogenis), one invasive species (Round Goby, Neogobius melanostomus) and an additional 78 native species from two large Great Lakes tributary rivers in southern Ontario, Canada; the Grand River and the Sydenham River. Out of 82 fish species detected in both rivers using capture-based and eDNA methods, our eDNA method detected 86.2% and 72.0% of the fish species in the Grand River and the Sydenham River, respectively, which included our four target species. Our analyses also identified significant positive and negative species co-occurrence patterns between our target species and other identified species. Our results demonstrate that eDNA metabarcoding that targets the fish community as well as individual species of interest provides a better understanding of factors affecting the target species spatial distribution in an ecosystem than possible with only target species data. Additionally, eDNA is easily implemented as an initial survey tool, or alongside capture-based methods, for improved mapping of species distribution patterns.

opencc-zeroDec 2016View details →

Data from: Strong population genetic structure of an invasive species, Rhynchophorus ferrugineus (Olivier), in southern China

The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier), was initially reported in China in the 1990s and is now considered one of the most successful invasive pests of palm plants in the country. A total of 14 microsatellite loci and one mitochondrial cytochrome oxidase subunit Ι (cox I) gene fragment were used to investigate the genetic characteristics and structure of R. ferrugineus in southern China. High levels of genetic differentiation among populations and significant correlations between genetic and geographical distances indicated an important role of geographical distance in the distribution of the RPW in southern China. High gene flow between Fujian and Taiwan province populations illustrated the increased effects of frequent anthropogenic activities on gene flow between them. Genetic similarity (i.e., haplotype similarity) indicated that RPW individuals from Taiwan and Fujian invaded from a different source than those from Hainan. To some extent, the genetic structure of the RPW in southern China correlated well with the geographic origins of this pest. We propose that geographical distance, anthropogenic activities and the biological attributes of this pest are responsible for the distribution pattern of the RPW in southern China. The phylogenetic analysis suggests that the most likely native sources of the RPW in southern China are India, the Philippines, and Vietnam.

Data from: Effect of plant root symbionts on performance of native woody species in competition with an invasive grass in multispecies microcosms

The majority of terrestrial plants form mutualistic associations with arbuscular mycorrhizal fungi (AMF) and rhizobia (i.e. nitrogen fixing bacteria). Understanding these associations has important implications for ecological theory and for restoration practice. Here we tested whether the presence of AMF and rhizobia influence the performance of native woody plants invaded by a non-native grass in experimental microcosms. We planted eight plant species (i.e. Acacia acuminata, A. microbotrya, Eucalyptus loxophleba subsp. loxophleba, E. astringens, Calothamnus quadrifidus, Callistemon phoeniceus, Hakea lissocarpha and H. prostrata) in microcosms of field-conditioned soil with and without addition of AMF and rhizobia in a fully factorial experimental design. After seedling establishment, we seeded half the microcosms with an invasive grass Bromus diandrus. We measured shoot and root biomass of native plants and Bromus, and on roots, the percentage colonization by AMF, number of rhizobia-forming nodules and number of proteaceous root clusters. We found no effect of plant root symbionts or Bromus addition on performance of myrtaceous, and as predicted, proteaceous species as they rely little or not at all on AMF and rhiozbia. Soil treatments with AMF and rhiozbia had a strong positive effect (i.e. larger biomass) on native legumes (A. microbotrya and A. acuminata). However, the beneficial effect of root symbionts on legumes became negative (i.e. lower biomass and less nodules) if Bromus was present, especially for one legume, i.e. A. acuminata, suggesting a disruptive effect of the invader on the mutualism. We also found a stimulating effect of Bromus on root nodule production in A. microbotrya and AMF colonization in A. acuminata which could be indicative of legumes' increased resource acquisition requirement, i.e. for nitrogen and phosphorus, respectively, in response to the Bromus addition. We have demonstrated the importance of measuring belowground effects because the aboveground effects gave limited indication of the effects occuring belowground.

opencc-zeroSep 2019View details →

Data from: Network-scale effects of invasive species on spatially-structured amphibian populations

<p>Understanding the factors affecting the dynamics of spatially-structured populations (SSP) is a central topic of conservation and landscape ecology. Invasive alien species are increasingly important drivers of the dynamics of native species. However, the impacts of invasives are often assessed at the patch scale, while their effects on SSP dynamics are rarely considered. We used long-term abundance data to test whether the impact of invasive crayfish on subpopulations can also affect the whole SSP dynamics, through their influence on source populations. From 2010 to 2018, we surveyed a network of 58 ponds and recorded the abundance of Italian agile frog clutches, the occurrence of an invasive crayfish, and environmental features. Using Bayesian hierarchical models, we assessed relationships between frog abundance in ponds and a) environmental features; b) connectivity within the SSP; c) occurrence of invasive species at both the patch- and the SSP-levels. If spatial relationships between ponds were overlooked, we did not detect effects of crayfish presence on frog abundance or trends. When we jointly considered habitat, subpopulation, and SSP features, processes acting at all these levels affected frog abundance. At the subpopulation scale, frog abundance in a year was related to habitat features, but was unrelated to crayfish occurrence at that site during the previous year. However, when we considered the SSP level, we found a strong negative relationship between frog abundance in a given site and crayfish frequency in surrounding wetlands during the previous year. Hence, SSP-level analyses can identify effects that would remain unnoticed when focussing on single patches. Invasive species can affect population dynamics even in not invaded patches, through the degradation of subpopulation networks. Patch-scale assessments of the impact of invasive species can thus be insufficient: predicting the long-term interplay between invasive and native populations requires landscape-level approaches accounting for the complexity of spatial interactions.</p>

Data from: Using public surveys to reliably and rapidly estimate the distributions of multiple invasive species on the Andaman archipelago

To effectively manage multiple biological invasions, information on their distributions must be generated rapidly and over large spatial scales. Using public surveys in a false-positive occupancy framework, we reliably estimate the distributions of three synanthropic invasive species on the Andaman Islands.

opencc-zeroDec 2014View details →

Data from: Modeling spatial expansion of invasive alien species: relative contributions of environmental and anthropogenic factors to the spreading of the harlequin ladybird in France

Species distribution models (SDM) have often been used to predict the potential ranges of introduced species and prioritize management strategies. However, this approach assumes equilibrium between occurrences and environmental gradients, an assumption which is violated during the invasion process, where many suitable sites are empty because the species has not yet reached them. Here we considered the invasive ladybird Harmonia axyridis as a case study to show the benefits of using a dynamic colonization–extinction model that does not assume equilibrium. We used a multi-year occupancy model incorporating environmental, anthropogenic and neighborhood effects, to identify factors that explained spreading variation of this species in France from 2004, when only a few occupied sites were detected, to 2011. We found that anthropogenic factors (urbanization, agriculture, vineyards, and presence/absence of highways) explained more variation in the diffusion process than environmental factors (winter and summer temperatures, wind-speed, and rainfall). The surface of urbanization was the major anthropogenic factor increasing the probability of colonization. The average summer temperature was the main environmental factor affecting colonization, with a negative effect when high or low. The neighborhood effect revealed that colonization was mostly influenced by contributions coming from a radius of 24 km around the focal cell. The contribution of neighborhood decreases over time, suggesting that H. axyridis is reaching its equilibrium in France. This is confirmed by the small discrepancy observed between the performance of our approach and a SDM approach when predicting a single year occupancy pattern at the end of the study period. Our approach has the advantage of explicitly modelling the state of the biological system during the spatial expansion and identifying colonization constraints. This allows managers to explore the effect of different actions on the system at key moments of the invasion process, hence providing a powerful approach to prioritize management strategies.

opencc-zeroDec 2011View details →

Data from: An invasive species reverses the roles in a host-parasite relationship between bitterling fish and unionid mussels

The impact of multiple invading species can be magnified due to mutual facilitation, termed "invasional meltdown", but invasive species can also be adversely affected by their interactions with other invaders. Using a unique reciprocal host-parasite relationship between a bitterling fish, Rhodeus amarus, and unionid mussels, we show that an invasive mussel reverses the roles in the relationship. Bitterling lay their eggs into mussel gills, and mussel larvae parasitize fish. Bitterling recently colonized Europe and parasitize all sympatric European mussels, but are unable to utilize a recently invasive mussel, Anodonta woodiana. The parasitic larvae of A. woodiana successfully develop on R. amarus, while larvae of European mussels are rejected by bitterling. This demonstrates that invading species may temporarily benefit from a coevolutionary lag by exploiting evolutionarily naïve hosts, but the resulting relaxed selection may facilitate its exploitation by subsequent invading species, leading to unexpected consequences for established interspecific relationships.

opencc-zeroDec 2011View details →

Data from: Invasion facilitates hybridization with introgression in the Rattus rattus species complex

Biological invasions result in novel species interactions, which can have significant evolutionary impacts on both native and invading taxa. One evolutionary concern with invasions is hybridization among lineages that were previously isolated, but make secondary contact in their invaded range(s). Black rats, consisting of several morphologically very similar but genetically distinct taxa that collectively have invaded six continents, are arguably the most successful mammalian invaders on the planet. We used mitochondrial cytochrome b sequences, two nuclear gene sequences (Atp5a1 and DHFR), and nine microsatellite loci to examine the distribution of three invasive black rat lineages (R. tanezumi, R. rattus I, and R. rattus IV) in the U.S. and Asia, and determine the extent of hybridization among these taxa. Our analyses revealed two mitochondrial lineages that have spread to multiple continents, including a previously undiscovered population of R. tanezumi in the southeastern U.S., whereas the third lineage (R. rattus IV) appears to be confined to Southeast Asia. Analyses of nuclear DNA (both sequences and microsatellites) suggested significant hybridization is occurring among R. tanezumi and R. rattus I in the U.S., and also suggest hybridization between R. tanezumi and R. rattus IV in Asia, although further sampling of the latter species pair in Asia is required. Furthermore, microsatellite analyses suggest unidirectional introgression from both R. rattus I and R. rattus IV into R. tanezumi. Within the U.S., introgression appears to be occurring to such a pronounced extent that we were unable to detect any nuclear genetic signal for R. tanezumi, and a similar pattern was detected in Asia.

opennotspecifiedDec 2004View details →

FIGURES 1–14, Sophonia species. 1–11 in On the identity of an invasive leafhopper on Hawaii (Hemiptera, Cicadellidae, Nirvaninae)

FIGURES 1–14, Sophonia species. 1–11, Sophonia orientalis (Matsumura), 1–7, 10 Hawaii specimen, 8, 9, 11 Madeira specimen. 1, head and thorax; 2, fore wing; 3, stype; 4, subgenital plate; 5, male pygofer and Xth segment; 6, connective; 7, pygofer process; 8, aedeagus (ventroposterior view); 9, 10, aedeagus (left lateral view); 11, aedeagus (posterior view); 12–14, Sophonia longitudinalis (Distant), aedeagus, left lateral view; 12, China; 13, India (Lunglei); 14, Sri Lanka.

FIGURE 5 in On the evolution of the species complex Pachycondyla chinensis (Hymenoptera: Formicidae: Ponerinae), including the origin of its invasive form and description of a new species

FIGURE 5. Characters of male coloration and mandible of P. nakasujii (A, B), P. chinensis (C, D) and P. luteipes (E, F). Black arrows indicate the mandible.

FIGURE 6 in On the evolution of the species complex Pachycondyla chinensis (Hymenoptera: Formicidae: Ponerinae), including the origin of its invasive form and description of a new species

FIGURE 6. Currently known distribution of P. nakasujii (A) and P. chinensis (B) in Japan. Each dot may indicate more than one site if they are located less than 20 km apart.

FIGURE 2 in On the evolution of the species complex Pachycondyla chinensis (Hymenoptera: Formicidae: Ponerinae), including the origin of its invasive form and description of a new species

FIGURE 2. Mean (± SD) of the biometric measurements of P. nakasujii and P. chinensis (n = 13 and 35, respectively).

FIGURE 4 in On the evolution of the species complex Pachycondyla chinensis (Hymenoptera: Formicidae: Ponerinae), including the origin of its invasive form and description of a new species

FIGURE 4. Characters of worker propodeum and petiole. The left side of worker propodeum and petiole of P. nakasujii (A), P. chinensis (C) and P. luteipes (E), and the posterior face of worker petiole of P. nakasujii (B), P. chinensis (D) and P. luteipes (F) (Scanning electron microscopy photographs). Horizontal white arrow: PW. Also see Japanese Ant Database Group (2003).

FIGURE 1 in On the evolution of the species complex Pachycondyla chinensis (Hymenoptera: Formicidae: Ponerinae), including the origin of its invasive form and description of a new species

FIGURE 1. Bayesian phylogenetic tree of the species complex Pachycondyla chinensis based on mitochondrial sequences of the COI region. The corresponding posterior probabilities (≥0.70) are shown by the branch. The horizontal bar represents a distance of 0.1 substitutions per site. GenBank accession numbers are shown in parentheses.