A macroecological perspective of diversity patterns in the freshwater realm

Department of Biology, University of Oulu, Oulu, Finland
Freshwater Biology (Impact Factor: 2.91). 08/2011; 56(9):1703 - 1722. DOI: 10.1111/j.1365-2427.2011.02610.x

ABSTRACT Summary1. The aim of this paper is to review literature on species diversity patterns of freshwater organisms and underlying mechanisms at large spatial scales.2. Some freshwater taxa (e.g. dragonflies, fish and frogs) follow the classical latitudinal decline in regional species richness (RSR), supporting the patterns found for major terrestrial and marine organism groups. However, the mechanisms causing this cline in most freshwater taxa are inadequately understood, although research on fish suggests that energy and history are major factors underlying the patterns in total species and endemic species richness. Recent research also suggests that not all freshwater taxa comply with the decline of species richness with latitude (e.g. stoneflies, caddisflies and salamanders), but many taxa show more complex geographical patterns in across-regions analyses. These complexities are even more profound when studies of global, continental and regional extents are compared. For example, clear latitudinal gradients may be present in regional studies but absent in global studies (e.g. macrophytes).3. Latitudinal gradients are often especially weak in the across-ecosystems analyses, which may be attributed to local factors overriding the effects of large-scale factors on local communities. Nevertheless, local species richness (LSR) is typically linearly related to RSR (suggesting regional effects on local diversity), although saturating relationships have also been found in some occasions (suggesting strong local effects on diversity). Nestedness has often been found to be significant in freshwater studies, yet this pattern is highly variable and generally weak, suggesting also a strong beta diversity component in freshwater systems.4. Both geographical location and local environmental factors contribute to variation in alpha diversity, nestedness and beta diversity in the freshwater realm, although the relative importance of these two groups of explanatory variables may be contingent on the spatial extent of the study. The mechanisms associated with spatial and environmental control of community structure have also been inferred in a number of studies, and most support has been found for species sorting (possibly because many freshwater studies have species sorting as their starting point), although also dispersal limitation and mass effects may be contributing to the patterns found.5. The lack of latitudinal gradients in some freshwater taxa begs for further explanations. Such explanations may not be gained for most freshwater taxa in the near future, however, because we lack species-level information, floristic and faunistic knowledge, and standardised surveys along extensive latitudinal gradients. A challenge for macroecology is thus to use the best possible species-level information on well-understood groups (e.g. fish) or use surrogates for species-level patterns (e.g. families) and then develop hypotheses for further testing in the freshwater realm. An additional research challenge concerns understanding patterns and mechanisms associated with the relationships between alpha, beta and gamma components of species diversity.6. Understanding the mechanistic basis of species diversity patterns should preferably be based on a combination of large-scale macroecological and landscape-scale metacommunity research. Such a research approach will help in elucidating patterns of species diversity across regional and local scales in the freshwater realm.

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Available from: Jani Heino, Jul 07, 2015
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    • "The species sorting paradigm emphasises niche patterns, assuming that habitat patches differ with regard to environmental conditions (Logue et al. 2011, Presley et al. 2012). Moreover, resource or environmental gradient influences strongly on the local demography of species and the outcome of local species interactions that site quality and dispersal jointly affect local community composition (Leibold et al. 2004, Heino 2011). As expected, our results gave support for species sorting in determining the variation in lake and river macrophyte community compositions. "
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    ABSTRACT: Metacommunity paradigms are increasingly studied to explain how environmental control and spatial patterns determine variation in community composition. However, the relative importance of these patterns on biological assemblages among different habitats is not well known. We investigated the relative roles of local, catchment and spatial variables based on overland and watercourse distances in explaining the variation of community structure of lake and river macrophytes in two large river basins at two spatial extents (within and across river basins). Partial redundancy analysis was used to explore the share of variability in macrophyte communities attributable to local environmental conditions, catchment land cover and space (generated with Principle Coordinates of Neighbour Matrices). We found that local variables had the highest effect on both lake and river macrophyte communities, followed by catchment variables. Space had no or only marginal influence on the community structure regardless of used distance measure. Total phosphorus, conductivity and turbidity of the local variables contributed most for lake macrophytes, whereas pH and color had largest independent contribution for variation in river macrophytes. Size of catchment area and proportion of lakes and agriculture were the most important catchment variables in both habitats. The strong importance of environmental control suggests that both lake and river macrophyte communities are structured by species sorting. This finding gives support to the validity of assessment systems based on the European Water Framework Directive.
    Community Ecology 06/2015; 16(1). DOI:10.1556/168.2015.16.1.9 · 1.20 Impact Factor
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    • "One might argue that large environmental gradients should lead to different gradient structures, whereas small environmental gradients should lead to nestedness (Heino, 2011). However, to our knowledge, no study has shown the effects of increasing environmental gradient lengths on metacommunity structures, although some have shown the effects of increasing environmental heterogeneity on increasingly more segregated distributions of species across a set of sites (Heino, 2013; McCreadie & Bedwell, 2013). "
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    ABSTRACT: 1. 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. 2. 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. 3. 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. 4. 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.
    Freshwater Biology 04/2015; 60:973-988. · 2.91 Impact Factor
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    • "Most stream studies have found that environmental control (e.g. in terms of stream size, velocity, acidity, nutrients) prevails over spatial (e.g. dispersal) constraints (Potapova & Charles, 2002; Mykr€ a et al., 2007; Heino & Mykr€ a, 2008; Landeiro et al., 2011; Siqueira et al., 2012b; G€ othe, Angeler & Sandin, 2013a). However, within the same set of sites and, therefore, the same spatial extent, some studies have found that differently dispersing organisms show different spatial structuring and environmental control of community structure (Thompson & Townsend, 2006; Maloney & Munguia, 2011; Astorga et al., 2012). "
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    ABSTRACT: 1. Metacommunity ecology addresses the situation where sets of local communities are connected by the dispersal of a number of potentially interacting species. Aquatic systems (e.g. lentic versus lotic versus marine) differ from each other in connectivity and environmental heterogeneity, suggesting that metacommunity organisation also differs between major aquatic systems. Here, we review findings from observational field studies on metacommunity organisation in aquatic systems. 2. Species sorting (i.e. species are 'filtered' by environmental factors and occur only at environmen-tally suitable sites) prevails in aquatic systems, particularly in streams and lakes, but the degree to which dispersal limitation interacts with such environmental control varies among different systems and spatial scales. For example, mainstem rivers and marine coastal systems may be strongly affected by 'mass effects' (i.e. where high dispersal rates homogenise communities to some degree at neighbouring localities, irrespective of their abiotic and biotic environmental conditions), whereas isolated lakes and ponds may be structured by dispersal limitation (i.e. some species do not occur at otherwise-suitable localities simply because sites with potential colonists are too far away). Flow directionality in running waters also differs from water movements in other systems, and this differ-ence may also have effects on the role of dispersal in different aquatic systems. 3. Dispersal limitation typically increases with increasing spatial distance between sites, mass effects potentially increase in importance with decreasing distance between sites, and the dispersal ability of organisms may determine the spatial extents at which species sorting and dispersal processes are most important. 4. A better understanding of the relative roles of species sorting, mass effects and dispersal limitation in affecting aquatic metacommunities requires the following: (i) characterising dispersal rates more directly or adopting better proxies than have been used previously; (ii) considering the nature of aquatic networks; (iii) combining correlative and experimental approaches; (iv) exploring temporal aspects of metacommunity organisation and (v) applying past approaches and statistical methods innovatively for increasing our understanding of metacommunity organisation.
    Freshwater Biology 04/2015; 60:845-869. DOI:10.1111/fwb.12533 · 2.91 Impact Factor