@article {4214, title = {Determinants of local and regional communities in intermittent and perennial headwaters of the Bolivian Amazon}, journal = {Freshwater Biology}, year = {2016}, abstract = {

SUMMARY

1. 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.
2. 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 a-diversity, but higher b-diversity, than perennial (PER) sites, due to local, negative effect of drying combined with the existence of multiple recovery stages at the network scale.

3. 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{\textendash}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.

4. b-diversity analyses confirmed that invertebrate and fish metacommunities were not at the same recovery stage because (i) b-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 b-diversity was higher at INT than at PER sites, but invertebrate b-diversity was similar; and (iii) physical distances were correlated with the turnover component of invertebrate b-diversity but with the nestedness component for fish.

5. 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.

}, doi = {doi:10.1111/fwb.12706}, author = {T. Datry and N. Moya and J. Zubieta and Thierry Oberdorff} } @article {4213, title = {Metacommunity patterns across three Neotropical catchments with varying environmental harshness}, journal = {Freshwater Biology}, volume = {61}, year = {2016}, pages = {277-292}, abstract = {

SUMMARY

1. 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.

2. 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.

3. 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.
4. 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.
5. 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.

}, doi = {doi:10.1111/fwb.12702}, author = {T. Datry and A.S. Melo and N. Moya and J. Zubieta and E. De La Barra and Thierry Oberdorff} } @article {4050, title = {Is drift the primary process promoting the resilience of river invertebrate communities? A manipulative field experiment in an intermittent alluvial river}, journal = {Freshwater Biology}, year = {2015}, abstract = {

ABSTRACT: 1. In river systems, aquatic invertebrate communities are surprisingly persistent over time and generally recover quickly from disturbances. Drift has long been viewed as the primary process promoting this resilience, and it plays a important role in predictive models of community composition and concepts in lotic ecology. More recently, other processes such as vertical migration from the hyporheic zone, aerial oviposition from distant refuges and the use of resistance forms (e.g. diapause) have received greater recognition and support for their importance. 2. In this study, the view that drift is the primary process promoting invertebrate community resilience was challenged in an intermittent alluvial river using reach-scale flow manipulations. First, six treatment channels were completely dried for 1 week, while three others were left flowing to be used as controls. Second, flow was re-established in channels and drift was either allowed or blocked for a 4-week period. Third, during this period the resilience of community structure, composition and function was compared between treatments, and the potential for colonisation from the drift, hyporheic zone, aerial oviposition and resistance forms was measured. 3. Communities recovered after only 2 weeks in all of the previously dried channels, and contrary to our hypotheses, invertebrate community structure, composition and functional trait composition were not altered by blocking drift, indicating it was not the primary process promoting resilience in this river. 4. Three lines of evidence suggested colonisation from the hyporheic zone and not aerial oviposition nor resistance forms promoted resilience following rewetting including the following: (i) finding all common benthic taxa in the hyporheic zone during the drying event, (ii) a distinct decrease in invertebrate size upon rewetting in all treatment channels and (iii) a negative correlation between resilience and water table depth. 5. This experiment highlighted the potential importance of the hyporheic zone as a key source of colonisation in alluvial rivers and emphasises the need for a three-dimensional perspective when considering community resilience in rivers. Adaptive management approaches are needed to direct attention to sources (e.g. hyporheic zone) that are essential to promoting community resilience in rivers facing increased pressures due to climate change, water abstraction and flow regime alteration.

}, doi = {DOI:10.1111/fwb.12658}, author = {R. Vander Vorste and F. Malard and T. Datry} } @article {4051, title = {Ecological research and management of intermittent rivers: an historical review and future directions}, journal = {Freshwater Biology}, year = {2015}, abstract = {

ABSTRACT: 1. Rivers and streams that do not flow permanently (herein intermittent rivers; IRs) make up a large proportion of the world{\textquoteright}s inland waters and are gaining widespread attention. We review the research on IRs from its early focus on natural history through to current application in management and policy. 2. The few early studies of the ecology of IRs were largely descriptive. Nevertheless, in the 1970s, synthesis of this sparse research complemented work on temporary standing waters to found a powerful framework for much of the subsequent research on IRs. 3. Research on the ecology and biogeochemistry of IRs continues to fuel our understanding of resistance and resilience to drying and flooding as disturbances. Syntheses of the growing literature, including cross-continental and cross-climate comparisons, are revealing the generality and individuality of ecological and ecosystem responses to flow cessation and surface water loss. Meanwhile, increasing numbers of experiments test the causality of these responses. 4. Much of the increased consideration of IRs in research, management and policy is driven by the observed and projected shifts in flow regimes from perennial to intermittent associated with changes in land and water use and climate, superimposed on the high incidence of natural intermittency. The need to protect and better manage IRs is prompting researchers to develop new or modified methods to monitor flow status and assess the ecological condition of these systems. 5. Intermittent river research and management will benefit from greater exploration of aquatic{\textendash}terrestrial linkages, wet{\textendash}dry cycling and temporal dynamics, more-detailed mapping and predictive modelling of flow intermittency and the application of metapopulation and metacommunity concepts alongside multiple-stressors and novel-ecosystems research. By building on existing knowledge, continuing to develop quantitative models and distribution maps and using experiments to test hypotheses and concepts, we can further ecological understanding and wise management of these ubiquitous ecosystems.

}, doi = {DOI:10.1111/fwb.12646}, author = {C. Leigh and A.J. Boulton and J. Courtwright and T. Datry} } @article {4049, title = {Invertebrate assemblage responses and the dual roles of resistance and resilience to drying in intermittent rivers}, journal = {Aquatic Sciences}, year = {2015}, abstract = {

ABSTRACT: Intermittent rivers are naturally dynamic ecosystems in which flow cessation and riverbed drying cause temporal fluctuations in aquatic biodiversity. We analysed datasets from intermittent rivers in different climate zones across the world to examine responses of aquatic macroinvertebrate assemblages to drying, in relation to both taxonomic composition and traits of resistance and resilience. First, we compared the differences in taxonomic richness and turnover and in trait diversity, richness and redundancy before and after intermittent sites dried with the differences in concurrently sampled perennial sites. We found such high levels of variation in the before-after differences at intermittent and perennial sites that we could not detect statistical differences between them. Second, we examined the effects of climate (arid, Mediterranean, temperate) and durations of dry and post-dry (flowing) periods on responses to drying at intermittent sites. Only climate had a detectable effect; the proportion of taxa at intermittent sites that persisted through drying-rewetting phases was greatest in arid-zone rivers. Regardless of climate, the invertebrates that persisted at intermittent sites were dominated by taxa resistant to drying. By contrast, taxa that persisted at perennial sites had fewer traits conferring resistance but more conferring resilience. The contributions of resistance and resilience combined with the presence of both intermittent and perennial reaches likely supports the long-term stability and persistence of communities in intermittent rivers, despite the inherently high variation in short-term responses to drying.

}, doi = {DOI:10.1007/s00027-015-0427-2 }, author = {C. Leigh and N. Bonada and A.J. Boulton and B. Hugueny and S.T. Larned and R. Vander Vorste and T. Datry} } @article {4048, title = {Towards understanding the organisation of metacommunities in highly dynamic ecological systems }, journal = {Oikos}, year = {2015}, abstract = {

ABSTRACT: Community ecology recognises today that local biological communities are not only affected by local biotic interactions and abiotic environmental conditions, but also by regional processes (e.g. dispersal). While much is known about how metacommunities are organised in space in terrestrial, marine and freshwater ecological systems, their temporal variations remain poorly studied. Here, we address the question of the dynamics of metacommunities in highly variable systems, using intermittent rivers (IRs), those rivers which temporarily stop flowing or dry up, as a model system. We first review how habitat heterogeneity in space and time influences metacommunity organisation. Second, we compare the metacommunities in IRs to those in perennial rivers (PRs) and develop the idea that IRs could undergo highly dynamic shifts due to the temporal variability in local and regional community processes. Third, we develop the idea that in IRs, metacommunities of the wet and dry phases of IRs are closely intertwined, thereby increasing even more their respective temporal dynamics. Last, we provide a roadmap to stimulate further conceptual and empirical developments of metacommunity research and identify possible applications for improving the management of IRs and other highly dynamic ecological systems.

}, doi = {doi: 10.1111/oik.02922}, author = {T. Datry and N. Bonada and J. Heino} }