Abstract
AbstractAimDespite increasing interest in β‐diversity, that is the spatial and temporal turnover of species, the mechanisms underlying species turnover at different spatial scales are not fully understood, although they likely differ among different functional groups. We investigated the relative importance of dispersal limitations and the environmental filtering caused by vegetation for local, multi‐taxa forest communities differing in their dispersal ability, trophic position and body size.LocationTemperate forests in five regions across Germany.MethodsIn the inter‐region analysis, the independent and shared effects of the regional spatial structure (regional species pool), landscape spatial structure (dispersal limitation) and environmental factors on species turnover were quantified with a 1‐ha grain across 11 functional groups in up to 495 plots by variation partitioning. In the intra‐region analysis, the relative importance of three environmental factors related to vegetation (herb and tree layer composition and forest physiognomy) and spatial structure for species turnover was determined.ResultsIn the inter‐region analysis, over half of the explained variation in community composition (23% of the total explained 35%) was explained by the shared effects of several factors, indicative of spatially structured environmental filtering. Among the independent effects, environmental factors were the strongest on average over 11 groups, but the importance of landscape spatial structure increased for less dispersive functional groups. In the intra‐region analysis, the independent effect of plant species composition had a stronger influence on species turnover than forest physiognomy, but the relative importance of the latter increased with increasing trophic position and body size.Main conclusionsOur study revealed that the mechanisms structuring assemblage composition are associated with the traits of functional groups. Hence, conservation frameworks targeting biodiversity of multiple groups should cover both environmental and biogeographical gradients. Within regions, forest management can enhance β‐diversity particularly by diversifying tree species composition and forest physiognomy.
Highlights
Since Whittaker (1960) defined β-diversity as the difference in species composition among sites, β-diversity has gained the increasing attention of ecologists
We examined the relative importance of dispersal limitations in shaping the species composition of local communities across a range of taxa ( “functional groups”) differing in their dispersal abilities, after controlling for the regional species pool and environmental filters ( “inter-region analysis”) (Figure 1b)
Our study showed that the relative contributions of the various mechanisms differ depending on the dispersal ability, trophic position or body size of the group of interest, in line with our hypotheses
Summary
Since Whittaker (1960) defined β-diversity as the difference in species composition among sites, β-diversity has gained the increasing attention of ecologists. To promote overall diversity within a region (γ-diversity), either α-diversity (the within-site species diversity) or β-diversity (Beck et al, 2012; Müller & Goßner, 2010) must be increased. The processes that promote compositional differentiation between local communities (species turnover) remain under debate and differ among habitat types and species groups (Aisen et al, 2017; Murphy et al, 2015; Zellweger et al, 2017). Four mechanisms are considered to account for the species composition of local communities (Figure 1a). At large spatial (inter-region) scales, historical biogeography (e.g. glaciation history), long-distance dispersal and macro-scale environmental filters shape the regional species pool that constrains the composition of local
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