A macroecological perspective of diversity patterns in the freshwater realm

Department of Biology, University of Oulu, Oulu, Finland
Freshwater Biology (Impact Factor: 2.74). 08/2011; 56(9):1703 - 1722. DOI: 10.1111/j.1365-2427.2011.02610.x


1. 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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    • "Vyverman et al., 2007; Vanormelingen et al., 2008b), whereas there are those who support the interplay of both factors (i.e. Verleyen et al., 2009; Hájek et al., 2011; Heino, 2011; De Bie et al., 2012; Souffreau et al., 2015) and those who did not find either space or environment to be significant (i.e. Beisner et al., 2006; Nabout et al., 2009). "

    Journal of Plankton Research 11/2015; 660(376):1190-1200. DOI:10.1093/plankt/fbv084 · 2.41 Impact Factor
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    • "Nestedness may occur in odonates when species are successively filtered under developmental constraints along important gradients such as shading and water permanence (McCauley et al., 2008; De Marco et al., 2015). Several studies report nested subsets for odonates (Sahl en & Ekestubbe, 2001; Craig et al., 2008; Kadoya et al., 2008; De Marco et al., 2015) and for other taxa of wetland ecosystems (Baber et al., 2004; Ruhi et al., 2013), but often the pattern looks weak for freshwater taxa in general (Heino, 2011), and traditional metrics are prone to type I error and overestimating nestedness (Fischer & Lindenmayer, 2002; Ulrich & Gotelli, 2007b). The Oklahoma resident damselflies appeared to have a loosely clumped nested pattern with statistical support from a relatively reliable metric (Almeida-Neto et al., 2008), agreeing with a study of stream odonates in Brazil (De Marco et al., 2015). "

    Freshwater Biology 11/2015; 60:2248-2260. · 2.74 Impact Factor
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    • "At large spatial scales, freshwater fishes adhere to both of biogeography's two major 'laws': fish richness increases with river basin area (Hugueny, 1989; Oberdorff et al., 1995; Albert et al., 2011), as predicted by the species–area relationship , and decreases with absolute latitude (L ev^ eque et al., 2008; Heino, 2011; Tisseuil et al., 2013), consistent with the latitudinal diversity gradient. This general congruence with the species–area and latitudinal patterns begs the question of whether fish diversity may be regulated by the same processes as terrestrial diversity. "
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    ABSTRACT: AimTo model the species–discharge relationship (SDR) for native freshwater fishes of the Western Hemisphere, to test whether the SDR is itself a function of latitude, and to create a conceptual framework to integrate the SDR with the species–area relationship and the latitudinal diversity gradient.LocationWestern Hemisphere rivers between 70°N and 50°S latitude.Methods Discharge and fish richness data were compiled for 107 rivers. Ordinary least squares and simultaneous autoregressive models were built for a hemispheric-scale SDR using one of three discharge (Q) measures: mean annual Q, annual low flow Q or annual high flow Q. Hemispheric-scale SDR residuals were used to test for distinct low, mid and high latitude groups and to deconstruct the SDR into separate models for each latitudinal group. Structural equation modelling (SEM) was then used to examine the combined effects of Q, river basin area, and latitude on fish richness.ResultsHemispheric-scale SDRs were significant (P ≤ 0.001) for each discharge measure. Model residuals showed that the SDR differs among tropical, subtropical and temperate realms. All deconstructed SDRs remained significant (P ≤ 0.001) and minimized the residual effect of latitude. The tropical SDR was significantly steeper (non-overlapping 95% confidence intervals) than the subtropical and temperate SDRs. For both hemispheric-scale and deconstructed SDRs, annual low flow Q was the best individual predictor of native fish richness. SEM analysis showed that Q may be an integrative measure of climate and physical habitat effects.Main conclusionsA single, hemispheric-scale SDR will underestimate fish richness in low latitude, tropical rivers and overestimate richness in high latitude, temperate rivers. Deconstructing the SDR into separate tropical, subtropical, and temperate models can account for much of this bias. Deconstructed SDRs also show that fish richness increases much more rapidly per-unit Q in tropical rivers than in subtropical or temperate rivers. Low flow Q is the strongest correlate of fish richness. And a preliminary, system-level model suggests that Q may play a central, integrative role in the regulation of freshwater diversity.
    Journal of Biogeography 09/2015; DOI:10.1111/jbi.12618 · 4.59 Impact Factor
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