Traditionally metacommunity studies have quantified the relative importance of dispersal and environmental processes on observed β-diversity. Separating β-diversity into its replacement and nestedness components and linking such patterns to metacommunity drivers can provide richer insights into biodiversity organization across spatial scales. It is often very difficult to measure actual dispersal rates in the field and to define the boundaries of natural metacommunities. To overcome those limitations, we revisited an experimental metacommunity dataset to test the independent and interacting effects of environmental heterogeneity and dispersal on each component of β-diversity. We show that the balance between the replacement and nestedness components of β-diversity resulting from eutrophication changes completely depending on dispersal rates. Nutrient enrichment negatively affected local zooplankton diversity and generated a pattern of β-diversity derived from nestedness in unconnected, environmentally heterogeneous landscapes. Increasing dispersal erased the pattern of nestedness, whereas the replacement component gained importance. In environmentally homogeneous metacommunities, dispersal limitation created community dissimilarity via species replacement whereas the nestedness component remained low and unchanged across dispersal levels. Our study provides novel insights into how environmental heterogeneity and dispersal interact and shape metacommunity structure.

No abstract

Biodiversity and nature values in anthropogenic landscapes often depend on land use practices and management. Evaluations of the association between management and biodiversity remain, however, comparatively scarce, especially in aquatic systems. Furthermore, studies also tend to focus on a limited set of organism groups at the local scale, whereas a multi-group approach at the landscape scale is to be preferred. This study aims to investigate the effect of pond management on the diversity of multiple aquatic organism groups (e.g. phytoplankton, zooplankton, several groups of macro-invertebrates, submerged and emergent macrophytes) at local and regional spatial scales. For this purpose, we performed a field study of 39 shallow man-made ponds representing five different management types. Our results indicate that fish stock management and periodic pond drainage are crucial drivers of pond biodiversity. Furthermore, this study provides insight in how the management of eutrophied ponds can contribute to aquatic biodiversity. A combination of regular draining of ponds with efforts to keep ponds free of fish seems to be highly beneficial for the biodiversity of many groups of aquatic organisms at local and regional scales. Regular draining combined with a stocking of fish at low biomass is also preferable to infrequent draining and lack of fish stock control. These insights are essential for the development of conservation programs that aim long-term maintenance of regional biodiversity in pond areas across Europe.

In metacommunity ecology, a major focus has been on combining observational and analytical approaches to identify the role of critical assembly processes, such as dispersal limitation and environmental filtering, but this work has largely ignored temporal community dynamics. Here, we develop a “virtual ecologist” approach to evaluate assembly processes by simulating metacommunities varying in three main processes: density‐independent responses to abiotic conditions, density‐dependent biotic interactions, and dispersal. We then calculate a number of commonly used summary statistics of community structure in space and time and use random forests to evaluate their utility for inferring the strength of these three processes. We find that (i) both spatial and temporal data are necessary to disentangle metacommunity processes based on the summary statistics we test, and including statistics that are measured through time increases the explanatory power of random forests by up to 59% compared to cases where only spatial variation is considered; (ii) the three studied processes can be distinguished with different descriptors; and (iii) each summary statistic is differently sensitive to temporal and spatial sampling effort. Including repeated observations of metacommunities over time was essential for inferring the metacommunity processes, particularly dispersal. Some of the most useful statistics include the coefficient of variation of species abundances through time and metrics that incorporate variation in the relative abundances (evenness) of species. We conclude that a combination of methods and summary statistics is probably necessary to understand the processes that underlie metacommunity assembly through space and time, but we recognize that these results will be modified when other processes or summary statistics are used.

Invasive alien species (IAS) are one of the most important drivers of species loss. A series of recent (inter)national policies and guidelines however did not prevent new introductions and further spread of non‐indigenous species. But instead of considering invasive plant species as a burden, the biomass production of IAS can be considered and used as an ecosystem service. To assess the possibilities for bioenergy production of four invasive alien plant species in Europe, Fallopia japonica, Heracleum mantegazzianum, Impatiens glandulifera and Solidago gigantea, we determined their biomass production, gross calorific value and biogas yield. The viability of the propagules after digestion was also tested to assess the dispersal risk related to the bioenergy chain. Fallopia japonica and S. gigantea achieved a high annual biomass yield of 8.6 ton DM per hectare. Impatiens glandulifera and H. mantegazzianum had a lower biomass production (5.8 and 6.0 ton DM ha−1). Without extra inputs or agronomic optimization of the crops, the anaerobic digestion of the studied invasive plant species achieved comparable energy outputs per hectare (28–88 GJ ha−1) as some of the current bioenergy systems. All propagules lost their viability after digestion. The risk of further invasion is thus minimized during the digestion process. However, caution during harvest and transport is required to prevent the spread of new propagules. The energetic valorization of the biomass of IAS can create an economic incentive for habitat restoration of invaded sites and offers the opportunity to reconcile the restoration of the invaded habitats with renewable energy goals. © 2015 Society of Chemical Industry and John Wiley & Sons, Ltd