Environmental and spatial controls of biotic assemblages in a discrete semi-terrestrial habitat: comparison of organisms with different dispersal abilities sampled in the same plots

Abstract

Aim The development of metacommunity theory inspired a series of studies exploring the importance of environmental and spatial effects on the composition of biotic assemblages. However, the comparison of different groups of organisms has been hampered by differences in sampling design, spatial scales or the environmental variables involved. Our aim was to test how dispersal ability affects metacommunity structure and associated species distributions by sampling different species groups in the same plots to avoid these problems. Location Western Carpathian Mountains (Europe).Methods In 191 fens we sampled the composition of diatom, bryophyte, vascular plant and mollusc assemblages, water chemistry, and macroclimatic data. We then generated spatial variables covering all relevant spatial scales using analysis of principal coordinates of neighbour matrices (PCNM). We applied the adjusted variation partitioning algorithm to quantify the effects of environment and space.Results Pure effects of water chemistry and space were highly significant for all groups of organisms. Spatial effects were stronger for groups with larger propagules (vascular plants, molluscs) than for those with smaller propagules (diatoms, bryophytes). Assemblages of macroscopic bryophytes were structured slightly less by geography and much more by environment than were those of microscopic diatoms. Vascular plant and mollusc assemblages turned out to be more spatially structured (as compared to diatom and bryophyte assemblages), with small differences between the two groups. Coarse-scale spatial effects dominated in the bryophyte metacommunity, while in the other groups, including diatoms, finer-scale effects were also important.Main conclusions Given that our analyses are based on a standardized sampling and analytical framework, our findings provide strong support for the hypothesis that both environmental and spatial variables structure metacommunities of organisms with very different dispersal abilities, including microscopic diatoms. In addition, we show for the first time that the strengths of these effects and their scale dependence may be predicted using important trait differences between organisms, for example differences in propagule size.

Stochastic distribution of small soil eukaryotes resulting from high dispersal and drift in a local environment

“…Differential dispersal abilities may lead to contrasting DDS patterns in macro-organisms and microorganisms (Nekola and White, 1999;Soininen et al, 2007;Hájek et al, 2011;Farjalla et al, 2012). These studies provide evidence that the effect of deterministic processes in community assembly increases with increasing body size, while stochastic processes are dominant in small organisms with passive dispersal.…”

“…There is an old assumption that free-living soil microbial eukaryotes do not face dispersal limitation (Finlay, 2002), but several molecular studies provide evidence for their biogeographic patterns (for example, Green et al, 2004;Bahram et al, 2013;Bates et al, 2013; but see Queloz et al, 2011). Recent findings also suggest that similarly to macro-organisms, microbes are influenced by neutral processes (for example, Cottenie 2005;Hájek et al, 2011;Astorga et al, 2012). Furthermore, some studies provide evidence for limited dispersal and biogeographic patterns in soil mesofauna (Wu et al, 2011;Porco et al, 2012).…”

“…Most of our knowledge about DDS of various organisms is derived from meta-analyses (Nekola and White, 1999;Soininen et al, 2007;Hanson et al, 2012) that comprise studies with different sampling grain and geographic scale, which may strongly bias the understanding of DDS relationships (Steinbauer et al, 2012). Thus simultaneous analyses of DDS in organisms with different dispersal traits (owing to their varying size and active vs passive motility) are needed for better understanding the relative contribution of deterministic and neutral processes (Soininen et al, 2007;Hájek et al, 2011;Bie et al, 2012). Small-scale studies are subject to fewer confounding factors such as climate, soil type, random environmental fluctuations and history and thus provide a good basis to determine neutral stochasticity (drift and dispersal limitation per se; Vellend et al, 2014).…”

Community structure of corticolous microalgae within a single forest stand: evaluating the effects of bark surface pH and tree species

“…Species richness of microalgae in biofilms was primarily correlated with the bark surface pH, which is determined by the host tree species. The effect of pH, indirectly coupled with the availability of nutrients (ellis 2012), has widely been recognised as a key factor structuring the diversity and community structure of aerial or semi-terrestrial microalgae (hoffmaNN 1989, johaNseN 2010, hájek et al 2011, ress & lowe 2013, as well as corticolous lichens and mosses (e.g., BarkmaN 1958, GoNzáLez-maNceBo et al 2003 and myxomycetes (scarBorouGh et al 2009). Many OTUs were only found in samples with higher bark pH, but we did not find any evidence of strictly acidophilic taxa.…”

Local and regional influences over soil microbial metacommunities in the Transantarctic Mountains

“…We assessed diversity patterns for both the total and the cyanobacterial subcomponent of soil bacterial communities, because cyanobacterial community composition appears to be related to local dispersal dynamics (i.e., proximity of an aquatic habitat to serve as a source for cyanobacterial propagules) (Wood et al 2008, Michaud et al 2012, Niederberger et al 2012, whereas total bacterial diversity patterns appear to be related to environmental gradients (Aislabie et al 2008, Tiao et al 2012. The nature of these relationships is linked to the ecological context-the characteristics of the organisms populating a metacommunity (i.e., dispersal ability [Fenchel and Finlay 2004, Shurin et al 2009, Hájek et al 2011, De Bie et al 2012 and prevalence of dormancy Lennon 2010, Lennon andJones 2011]), which in turn v www.esajournals.org determine how the metacommunity can respond to environmental gradients in a given landscape.…”