Do graminoid and woody invaders have different effects on native plant functional groups?

Alien Plants are Less Palatable to Pest Herbivores than Native Plants: Evidence from Cafeteria Experiments in Search of Suitable Plant Species to Restore Degraded Ecosystems

Nowadays, the ecology and evolutionary potential of alien species are the subjects of several ecological studies. The goal of this study was to compare the feeding preference of Arion ater on seedlings and leaves of alien and native plant species. Seedlings of three native species and one alien species were offered to slugs individually and in combination. Afterward, leaf discs from the native and alien species collected from the same source site of slug’s habitat were offered individually and in combination for slugs. When the new plant emerges, it constitutes a generous source of potential food and slugs would even feed on seedlings, which are not particularly palatable. Nonetheless, when given a choice, slug often preferentially feeds on some food items while ignoring others. Alien plants are more resistant to herbivory than native plants. There is a general tendency for alien species to be less palatable than native species. In general, slugs may eat a wide range of seedlings that are much more attractive than mature plants of the same species. Therefore, the native herbivores were found to attack native plants and promoted alien plants. Consequently, highly unacceptable alien species such as Eucalyptus globulus may play an important role in the restoration process.

Invasive legume affects species and functional composition of mountain meadow plant communities

Plant invasions are among the key drivers of global biodiversity and ecosystem change. They often cause reductions in native species richness and overall biodiversity. Nitrogen-fixing plants are problematic as they affect soil nutrient availability and outcompete species of nutrient-poor sites. Here we assessed the impacts of the legume Lupinus polyphyllus on species and functional diversity of mountain meadow communities in the UNESCO Biosphere Reserve Rhön. We compared species diversity (richness, evenness and effective species number), functional diversity (functional richness, evenness, divergence and dispersion) and similarity of plots in three characteristic vegetation types (Nardus grassland, mesic and wet mountain hay meadows) between different lupine cover classes. We calculated community weighted means (CWMs) of single plant traits and plotted them against lupine cover classes. The invasion of L. polyphyllus homogenizes vegetation composition since the similarity among plots of the different vegetation types increased with increasing lupine cover. It significantly affected species diversity in terms of richness and effective species number and the functional divergence of the vegetation. The trait set of species occurring together with lupine was shifted towards more competitive trait values. We demonstrate strongly negative impacts of L. polyphyllus on different mountain meadow vegetation types since L. polyphyllus, fosters the growth of competitive species and leads to overall more productive plant communities.

A broad framework to organize and compare ecological invasion impacts

Invasive species have transformed local, regional and global biotas; however, few generalities about the mechanisms driving impacts of invaders have emerged. To explain variation in impacts among studies, we propose a broad framework that separates drivers of impacts into universal and unique attributes of the invasive species and the invaded habitat. Universal attributes are relevant to all invasions whereas unique attributes are distinct to a specific invasion. For example, impacts associated with the abundance of any invader or the properties of a specific invader (e.g., a rare toxin) represent a universal and unique impact attribute. Through meta-analyses of aquatic field experiments, we demonstrate the utility of our framework, documenting that both the abundance and the taxonomic identity of the invader significantly influence invasion outcomes for marine and freshwater plant and animal invaders. Our review also highlights that many more experiments are needed to test for universal attributes, such as priority effects, age and size, and how the attributes of the invaded habitat further modify invasion impacts. We hope that our framework will stimulate experimental invasion ecology and begin to reconcile the idiosyncrasies that currently impede the development of a unified framework for invasion impacts.

A predictive framework and review of the ecological impacts of exotic plant invasions on reptiles and amphibians

The invasive spread of exotic plants in native vegetation can pose serious threats to native faunal assemblages. This is of particular concern for reptiles and amphibians because they form a significant component of the world's vertebrate fauna, play a pivotal role in ecosystem functioning and are often neglected in biodiversity research. A framework to predict how exotic plant invasion will affect reptile and amphibian assemblages is imperative for conservation, management and the identification of research priorities. Here, we present a new predictive framework that integrates three mechanistic models. These models are based on exotic plant invasion altering: (1) habitat structure; (2) herbivory and predator-prey interactions; (3) the reproductive success of reptile and amphibian species and assemblages. We present a series of testable predictions from these models that arise from the interplay over time among three exotic plant traits (growth form, area of coverage, taxonomic distinctiveness) and six traits of reptiles and amphibians (body size, lifespan, home range size, habitat specialisation, diet, reproductive strategy). A literature review provided robust empirical evidence of exotic plant impacts on reptiles and amphibians from each of the three model mechanisms. Evidence relating to the role of body size and diet was less clear-cut, indicating the need for further research. The literature provided limited empirical support for many of the other model predictions. This was not, however, because findings contradicted our model predictions but because research in this area is sparse. In particular, the small number of studies specifically examining the effects of exotic plants on amphibians highlights the pressing need for quantitative research in this area. There is enormous scope for detailed empirical investigation of interactions between exotic plants and reptile and amphibian species and assemblages. The framework presented here and further testing of predictions will provide a basis for informing and prioritising environmental management and exotic plant control efforts.