Editor's Choice September

We selected two meta-analysis papers as editor’s choice for the September issue. The meta-analysis authored by Albert and colleagues aimed to study to which degree ungulates act as an environmental filter for the dispersal of seeds. By relating patterns in dispersal to seed and plant traits, the authors provide insights that are of general importance to forecast the spread of plant species by their vertebrate herbivore hosts in temperate regions. Nearly half of the species studied appeared to be spread by ungulates. Typical traits were associated with different dispersal mechanisms, but their importance increased with the specificity of the dispersal mechanisms. Particularly surprising (to me at least) was the weak filtering effect of endozoochory on seed dispersal. It may thus be an important, but unpredictable or stochastic mechanism determining plant spread in highly heterogeneous and fragmented systems.

Tamburello and co-authors report on a meta-analysis and an experiment by which the effects of non-native seaweeds on native species and communities are studied along gradients of habitat degradation. The paper is one of the first to test to which degree interactions among aquatic plants hinge upon environmental context; more specifically whether interactions shift from negative to positive with increasing environmental severity. Relative to earlier work, the meta-analysis explores species interactions related to invasion by exotic plant species and in response to a stress gradient corresponding to a multivariate index of human impact. The meta-analysis shows that invasive seaweed tends to impact both producer diversity and consumer abundance strongly and negatively in pristine environments, but only modestly and even positively in increasingly human-impacted environments. This pattern was corroborated by the experiment. Exotic algae species are thus chiefly of concern in relatively pristine ecosystems but they may actually have beneficial effects on biodiversity in disturbed and human-influenced environments.

Dries Bonte

Editor in Chief

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