Contrasting metacommunity structure and beta diversity in an aquatic‐floodplain system

Abstract

Habitat connectivity and dispersal interact to structure metacommunities, but few studies have examined these patterns jointly for organisms across the aquatic-terrestrial ecotone. We assessed metacommunity structure and beta diversity patterns of instream benthic invertebrates, riparian carabid beetles (Order: Coleoptera; Family: Carabidae) and riparian spiders (Order: Araneae) at fifteen sites in a river-floodplain system. Sampling took place over a three-year period (2010)(2011)(2012) in the Rhine-Main-Observatory LTER site on the Kinzig River, central Germany. This allowed disentangling the combined influence, and temporal variability, of habitat connectivity (i.e. between aquatic and terrestrial) and dispersal ability (i.e. between spiders and beetles, and aerial and aquatic dispersing invertebrates) on the dominant paradigms structuring these metacommunities. We found mostly consistent differences in the manner that metacommunities were structured between groups, with lower levels of variability explained for beetles compared to the other groups. Beetles were consistently structured more by turnover than nestedness components, with greater beta diversity than expected by chance and a minor spatial compared to environmental signal emerging with variance partitioning. Conversely, spiders and benthic invertebrates had lower beta diversity and greater nestedness than null expectation, and a clearer spatial signal controlling metacommunity structure. Our results suggest varying levels of mass effects and species sorting shape river-floodplain metacommunities, depending on habitat connectivity and dispersal ability. That is, greater connectivity and lower fragmentation along the river compared to the terrestrial zone promoted mass effects, and differences in overall dispersal ability and mode (i.e. active and passive) for instream and riparian communities shifted paradigms between mass effects and species sorting.

Effects of dispersal and environmental heterogeneity on the replacement and nestedness components of β‐diversity

“…Because dispersal limitation interacts with eutrophication to create dissimilarity resulting mainly from nestedness in heterogeneous landscapes, we argue that sufficient habitat connectivity is crucial in allowing species to repopulate suitable sites and also to ensure high complementarity (replacement) among sites (Shurin 2001, Howeth andLeibold 2010). Based on our findings, it is conceivable that nestedness resulting from eutrophication will predominate among dispersal-limited groups and turnover will be more important for highly mobile groups within the same landscape (Tonkin et al 2016). As a result, different management strategies will often be needed to conserve α-and β-diversity of different organism groups.…”

“…β-diversity, here defined as the dissimilarity in species composition among a pair of sites, can be partitioned into two components: dissimilarity derived from species replacement and dissimilarity derived from nestedness (Baselga 2010, Legendre 2014. The replacement and nestedness components can contribute jointly to total dissimilarity among communities, but their relative importance will change depending on the ecological processes structuring metacommunities (Brendonck et al 2015, Tonkin et al 2016. The replacement and nestedness components can contribute jointly to total dissimilarity among communities, but their relative importance will change depending on the ecological processes structuring metacommunities (Brendonck et al 2015, Tonkin et al 2016.…”

Context dependency in biodiversity patterns of central German stream metacommunities

“…macroecology) where generalisations are more readily available (Lawton, 1999). For instance, there are often differences between different trait modalities, such as dispersal modes (Thompson & Townsend, 2006;Canedo-Arguelles et al, 2015;Tonkin et al, 2015b), or in the characteristics of the environmental setting (Heino et al, 2015d). As with community ecology in general (Lawton, 1999), context dependency in metacommunity structuring may emerge through differences in the characteristics of different organisms.…”

Severity Multipliers as a Methodology to Explore Potential Effects of Climate Change on Stream Bioassessment Programs

“…This aligns with a recent call for biomonitoring and bioassessment of freshwaters to consider metacommunity dynamics [56]. Recent evidence suggests that niche control (i.e., species sorting) in rivers is only part of the equation, with dispersal-related influences (e.g., mass effects, and dispersal limitation) playing a major role in structuring stream communities [50]. It is likely that dispersal limitation will play a key role in the outcome of future climate warming and related shifts in community composition, with many weak dispersers potentially not keeping up with climate change.…”

“…Nevertheless, aspects of connectivity of adjacent catchments will affect the dispersal of organisms in relation to moving temperature niches, including the level of movement within and between catchments. This will likely depend on the dispersal capacity of organisms [49,50]. For poor dispersers that cannot disperse across catchment boundaries (i.e., overland) in headwater streams, the summit-trap effect may play a role [21] (but see Isaak et al [51]).…”