Elements of metacommunity structure and community‐environment relationships in stream organisms

Abstract

Summary Most metacommunity studies aim to explain variation in community structure using environmental and spatial variables. An alternative is to examine patterns emerging at the level of an entire metacommunity, whereby six models of metacommunity structure (i.e. random, chequerboards, nestedness, evenly spaced, Gleasonian gradients and Clementsian gradients) can be examined. We aimed to test the fit of six competing models of metacommunity structure to extensive survey data on diatoms, bacteria, bryophytes and invertebrates from three drainage basins in Finland, along a latitudinal gradient from 66 °N to 70 °N. Species were mainly distributed independently of one another (following the Gleasonian model) in the southernmost drainage basin (66 °N), whereas there were discrete community types, with sets of species responding similarly along environmental gradients (following the Clementsian model), in the northernmost drainage basin (70 °N). The patterns found were not directly related to an expected relationships between environmental heterogeneity and metacommunity structures, but rather to the geographical location of the drainage basin. There is evidently among‐region variation in the best‐fit models of metacommunity structure of stream organisms. These metacommunity patterns may show some similarities among biologically disparate organismal groups sampled at the set of the same sites, although the underlying environmental drivers of those patterns may vary between the groups.

A comparative analysis of metacommunity types in the freshwater realm

“…First, most freshwater metacommunities in northern drainage basins are strongly dominated by rare species (bacteria: Heino et al. 2015b; diatoms: Soininen and Heino 2005; invertebrates: Heino 2005; bryophytes: Heino and Virtanen 2006; macrophytes: Alahuhta et al. 2014), so removing rare species would lead to unnatural results.…”

“…Second, our previous analyses have shown that the main patterns found by the EMS analyses do not typically change if rare species (i.e., those occurring at a single site) are removed (Heino et al. 2015b). …”

Unravelling the drivers of aquatic communities using disparate organismal groups and different taxonomic levels

“…We used different a-primer barcodes for each sample. The laboratory methods are presented in detail in Heino et al (2015). However, to extract as much DNA as possible, the following parts of the bacterial analysis differed from Heino et al (2015): Stage 2 was repeated 30 times instead of 25 times.…”

“…The laboratory methods are presented in detail in Heino et al (2015). However, to extract as much DNA as possible, the following parts of the bacterial analysis differed from Heino et al (2015): Stage 2 was repeated 30 times instead of 25 times. In Stage 3, total volume of one PCR reaction were 25 l containing 5 l GC-buffer, 0.5 l dNTP, 0.5 l Phusion Hot Start II High-Fidelity DNA Polymerase, 12.5 l sterile water (DNA Grade, DNASE, Protease free), 1 l A-primer, 1 l B-primer and 5 l bacterial sample.…”

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“…For example, desert rodent parasites (Dallas and Presley 2014) or small mammals in South American Atlantic Forest (Sancha et al 2014). Structures can also differ between different environmental set-310 tings (Heino, Nokela, et al 2015) or gradients of environmental change, such as between different forest types, as found for terrestrial gastropods along elevational gradients (Willig et al 2011). recently found considerable variation in EMS patterns in a variety of freshwater systems and organisms.…”