Search

Abstract: Biological invasions are a threat to biodiversity, society and the economy. There is an urgent need to provide evidence‐based assessments of the risks posed by invasive alien species (IAS) to prioritize action. Risk assessments underpin IAS policies in many ways: informing legislation; providing justification of restrictions in trade or consumer activities; prioritizing surveillance and rapid response. There are benefits to ensuring consistency in content of IAS risk assessments globally, and this can be achieved by providing a framework of minimum standards as a checklist for quality assurance. From a review of existing risk assessment protocols, and with reference to the requirements of the EU Regulation on IAS (1143/2014) and international agreements including the World Trade Organisation, Convention on Biological Diversity and International Plant Protection Convention, coupled with consensus methods, we identified and agreed upon 14 minimum standards (attributes) a risk‐assessment scheme should include. The agreed minimum standards were as follows: (1) basic species description; (2) likelihood of invasion; (3) distribution, spread and impacts; (4) assessment of introduction pathways; (5) assessment of impacts on biodiversity and ecosystems; (6) Assessment of impact on ecosystem services; (7) assessment of socio‐economic impacts; (8) consideration of status (threatened or protected) of species or habitat under threat; (9) assessment of effects of future climate change; (10) completion possible even when there is a lack of information; (11) documents information sources; (12) provides a summary in a consistent and interpretable form; (13) includes uncertainty; (14) includes quality assurance. In deriving these minimum standards, gaps in knowledge required for completing risk assessments and the scope of existing risk assessment protocols were revealed, most notably in relation to assessing benefits, socio‐economic impacts and impacts on ecosystem services but also inclusion of consideration of climate change. Policy implications. We provide a checklist of components that should be within invasive alien species risk assessments and recommendations to develop risk assessments to meet these proposed minimum standards. Although inspired by implementation of the European Union Regulation on invasive alien species, and as such developed specifically within a European context, the derived framework and minimum standards could be applied globally. [ABSTRACT FROM AUTHOR]

Abstract: 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. We developed a simple method to systematically rank IAS according to their maximum potential threat to biodiversity in the EU. We identified 1,323 species as potential candidates for listing, and evaluated them against their invasion stages and reported impacts, using information from databases and scientific literature. 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. Policy implications. We propose a systematic, proactive approach to selecting and prioritising IAS for risk assessment to assist European Union policy implementation. We assess an unprecedented number of species with potential to harm EU biodiversity using a simple methodology 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. [ABSTRACT FROM AUTHOR]

Plant communities are often dispersal-limited and zoochory can be an efficient mechanism for plants to colonize new patches of potentially suitable habitat. We predicted that seed dispersal by ungulates acts as an ecological filter - which differentially affects individuals according to their characteristics and shapes species assemblages - and that the filter varies according to the dispersal mechanism (endozoochory, fur-epizoochory and hoof-epizoochory). We conducted two-step individual participant data meta-analyses of 52 studies on plant dispersal by ungulates in fragmented landscapes, comparing eight plant traits and two habitat indicators between dispersed and non-dispersed plants. We found that ungulates dispersed at least 44% of the available plant species. Moreover, some plant traits and habitat indicators increased the likelihood for plant of being dispersed. Persistent or nitrophilous plant species from open habitats or bearing dry or elongated diaspores were more likely to be dispersed by ungulates, whatever the dispersal mechanism. In addition, endozoochory was more likely for diaspores bearing elongated appendages whereas epizoochory was more likely for diaspores released relatively high in vegetation. Hoof-epizoochory was more likely for light diaspores without hooked appendages. Fur-epizoochory was more likely for diaspores with appendages, particularly elongated or hooked ones. We thus observed a gradient of filtering effect among the three dispersal mechanisms. Endozoochory had an effect of rather weak intensity (impacting six plant characteristics with variations between ungulate-dispersed and non-dispersed plant species mostly below 25%), whereas hoof-epizoochory had a stronger effect (eight characteristics included five ones with above 75% variation), and fur-epizoochory an even stronger one (nine characteristics included six ones with above 75% variation). Our results demonstrate that seed dispersal by ungulates is an ecological filter whose intensity varies according to the dispersal mechanism considered. Ungulates can thus play a key role in plant community dynamics and have implications for plant spatial distribution patterns at multiple scales. [ABSTRACT FROM AUTHOR]

I H helix i and I H hibernica i share invasive characteristics, such as their evergreen leaves, persistence, and vegetative capabilities, but there are important ecological differences between the two species. Although both species are known to be problematic outside their natural ranges, invasive ivy populations consist more often of I H hibernica i than I H helix i , especially in forests (Clarke I et al i . 2006; Green I et al i . 2013). Triploid ivies have been found in co-occurring alien populations of I H helix i and I H hibernica i , suggesting they can hybridize, but to date no triploids have been found in Europe (Green I et al i . 2013). [Extracted from the article]

Many herbaceous and graminoid plants from open communities are characterized by their relatively small size and by seeds that appear to lack any clear traits for dispersal. Such syndrome is likely the result of several selective pressures and their tradeoffs acting together. Drawing on the putative relationship of these plants with large mammals that graze on them, with respect to defoliation and the dispersal of seeds (endozoochory), we included plant stature as a trait in a simulation model to elaborate on these animals' relative contribution in plant evolution. Different configurations of the landscape were used as a template, as these are known to affect the response of plants through additional costs levied in dispersal. As such, two herbivore parameters (the intensity of grazing and the efficacy of endozoochorous dispersal) were tested along with two parameters of the landscape (the proportion and connectivity of suitable habitat). Plants were allowed to evolve freely under these conditions, assuming that taller plants 1) produce more seeds and 2) have a more distant seed rain in wind dispersal, but 3) are also more likely to suffer failed reproduction because of herbivory. Our model confirmed the effects of landscape on the resulting dispersal capacity of plants, although these effects were readily overruled by the actions of grazers. We found the evolution of plant size to primarily result from the effects of defoliation, but also (though to a lesser degree) from endozoochory. This provides support for the adaptive value of unassisted dispersal syndromes in plants. Endozoochory also succeeded in maintaining increased population densities. However, these effects only hold when grazers sustain a considerable transfer of seeds towards suitable plant habitat. [ABSTRACT FROM AUTHOR]

Different species have different dispersal capabilities and in the field, species interact with each other within dynamic, heterogeneous and complex landscapes. While plants and certain herbivore species may disperse considerable distances by means of seed dispersal or flight, other herbivores (e.g. root-feeding nematodes or non-winged insect herbivores) are more limited in their dispersal capacities. This difference in dispersal capabilities results in mosaics of plant-herbivore interactions that shift over time and space leading to spatio-temporal variation in both the presence and absence of the species and their interactions. We developed an individual based simulation model in which we examined how multi-species interactions are affected by their mobility within structurally complex landscapes. The main objective was to address the consequences for the arms race between plant defence and herbivore resistance to changes in fundamental landscape and community attributes. We demonstrate that feedbacks between landscape structure, community structure and the specific dispersal rate of the species involved affect the evolutionary dynamics between plants and herbivore antagonists. While three-species interactions result in increased plant defence and herbivore resistance, effects of dispersal have diverse effects depending on the prevailing landscape structure. [ABSTRACT FROM AUTHOR]