Article

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

ABSTRACT

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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    • "Invertebrate samples were combined and preserved in 5% formalin, and animals were enumerated and identified to the lowest practical level (generally family or genera) in the laboratory using the Fern andez & Dom ınguez (2001) and Merritt & Cummins (1996) identification keys. South American invertebrates are still poorly known, but family-or genera-level resolution was previously shown to be sufficient to identify community patterns across disturbance (e.g.Datry et al., 2014;Datry et al., 2016a;Datry et al., 2016b) or large-scale environmental gradients (e.g.Heino, 2011), and it is commonly used for biomonitoring purposes (e.g.Moya et al., 2011)Fish communities were sampled by electrofishing along study reaches (~40 m long) that encompassed a complete set of geomorphological forms (e.g. riffles and pools). "
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    ABSTRACT: Most metacommunity studies indicate that dispersal processes play a minor role compared with species sorting in explaining metacommunity organisation, in particular, in stream systems. However, the role of dispersal could vary with environmental harshness, as a result of frequent resetting of community succession by disturbances and the selection of generalist species from regional species pools. The importance of dispersal may also be mitigated by species dispersal ability. In this study, we explored how species sorting and dispersal shaped invertebrate and fish metacommunities across streams in three tropical headwater catchments in Bolivia with contrasting environmental harshness, including flow regime, altitude and climate conditions. We addressed the hypothesis that the relative roles of dispersal and species sorting vary with environmental harshness: we predicted that the role of species sorting would predominate in benign conditions, whereas that of dispersal would predominate under moderate environmental harshness, and that neither dispersal nor species sorting would be relevant to explain metacommunities under high environmental harshness. We also hypothesised that the role of dispersal would decrease with increasing species dispersal ability. Although there was little or no spatial autocorrelation of environmental distances (i.e. environmental differences) across the headwater catchments, community similarity correlated more strongly with environmental than spatial distances among headwater sites that had low environmental harshness, but the opposite pattern was observed among sites with moderate environmental harshness. Under high environmental harshness, neither environmental harshness nor spatial distances between sites explained community similarity. Under moderate environmental harshness, the correlation between community similarity and spatial distances was the strongest for moderate dispersers of both invertebrates and fish. Yet, in contrast to fish, strongly dispersing invertebrate taxa were spatial structured, suggesting that they were not able to reach all sites as predicted. Our results suggest the role of dispersal might be underestimated, notably in systems prone to environmental harshness. Better proxies for dispersal, along with the use of spatial distances to account for resistance to animal movements in river systems and that account for flow magnitude and directionality, slope, riparian vegetation, wind and streambed roughness, may promote a more realistic integration of dispersal processes in basic and applied metacommunity research.
    Full-text · Article · Jan 2016 · Freshwater Biology
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    • "South American invertebrates are still poorly known, but such coarse resolution was shown to be sufficient to study community patterns across disturbance (e.g. Datry et al., 2014a ) or large-scale environmental gradients (e.g. Heino, 2011 ) and is commonly used for biomonitoring (e.g. Moya et al., 2011). "
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    ABSTRACT: The effect of drying events on aquatic biodiversity is still overlooked in wet Neotropical systems. Yet, the responses of local communities and metacommunities in these biodiversity hotspots may differ from what is reported in other areas. We addressed the effect of drying events on local and regional fish and macroinvertebrate communities in the headwaters of the Chipiriri River basin, in the wet Neotropical piedmont of Bolivia. According to current knowledge in intermittent rivers and ephemeral streams (IRES) ecology, we predicted that intermittent (INT) sites would harbour lower α-diversity, but higher β-diversity, than perennial (PER) sites, due to local, negative effect of drying combined with the existence of multiple recovery stages at the network scale. Although habitat variables were similar between INT and PER sites, local and regional diversity patterns differed. Local invertebrate communities were not different between site types as soon as 4–6 weeks after flow resumption. The proximity of colonist sources and frequent rainfall probably enhanced persistence through dry periods and high resilience. In contrast, fish communities were still poorer at INT than PER sites, indicating they were still in the process of recolonising upstream INT reaches. β-diversity analyses confirmed that invertebrate and fish metacommunities were not at the same recovery stage because (i) β-diversity of invertebrates was best explained by physical and environmental distances at both INT and PER sites, whereas that of fish was explained only by physical distances at INT sites; (ii) fish β-diversity was higher at INT than at PER sites, but invertebrate β-diversity was similar; and (iii) physical distances were correlated with the turnover component of invertebrate β-diversity but with the nestedness component for fish. Exploring regional community patterns in IRES and across biota with different dispersal abilities and modes can advance metacommunity theory and improve our ability to predict local community composition in dynamic ecosystems.
    Full-text · Article · Jan 2016 · Freshwater Biology
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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). "
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    ABSTRACT: Despite wide knowledge of environment–community relationships in inland waters, the relative effects of niche conditions (environment) and dispersal (space) on microorganism communities remain controversial. In lotic waters, non-directional processes (i.e. overland dispersal) and the unidirectional connectivity among sites control species distributions along a gradient. We aimed to detect phytoplankton biogeographical patterns in a large subtropical river (Uruguay River, 1150 km, Brazil) and to isolate the contributions of the environment (limnology, climate and topography) and space in shaping community structure. Phytoplankton (total and functional groups) and abiotic variables were sampled from a hydroplane in motion. To detect biogeographical patterns, we used Mantel's correlation test, and to evaluate the relative roles of environment and space, we used partial redundancy analysis with non-directional symmetrical and directional asymmetrical approaches. Similarity in phytoplankton composition decreased with distance, but only environment significantly explained this pattern. Space was not significant, considering non-directional and directional processes. Phytoplankton communities considering both individual species and their functional groups were more similar between closer sites, because niche conditions play the main role in shaping phytoplankton, not because dispersal is favored among nearby communities. The species-sorting model, based mostly on niche theory, was the main metacommunity mechanism for phytoplankton communities in this river basin.
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