Leigh, C., and F. Sheldon. Hydrological connectivity drives patterns of macroinvertebrate biodiversity in floodplain rivers of the Australian wet /dry tropics. Freshwater Biology

Freshwater Biology (Impact Factor: 2.74). 03/2009; 54(3):549–571. DOI: 10.1111/j.1365-2427.2008.02130.x
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1. Floodplain rivers in Australia's wet ⁄dry tropics are regarded as being among the most ecologically intact and bio-diverse lotic ecosystems in the world, yet there have been relatively few community-based studies of their aquatic fauna. 2. To investigate relationships between hydrological connectivity and biodiversity in the region, macroinvertebrates were collected from sites within two contrasting floodplain rivers, the 'tropical' Gregory River and 'dryland' Flinders River systems, during the dry season and analysed at various spatial scales. A subset of sites was re-sampled in the following dry season to explore temporal variation. The fauna consisted of 124 morphotaxa, dominated by gatherers and the Insecta. 3. As predicted, hydrological connectivity (the lotic or lentic status of waterbodies) had a major influence on macroinvertebrate assemblage composition and diversity, both in space and time. Assemblages from waterbodies with similar connection histories were most alike, and beta-diversity between assemblages was greatest between lotic and lentic waterbodies, tending to increase with increasing spatial separation. 4. At smaller spatial scales, a number of within-waterbody, habitat and water quality characteristics were important for explaining variation (61%) in the taxonomic organization of assemblages, and characteristics associated with primary productivity and habitat diversity were important for explaining variation (45%) in the functional organization of assemblages. However, much of the small-scale environmental variation across the study region appeared to be related to broad-scale variation in hydrological connectivity, which had both direct and indirect effects on macroinvertebrate assemblages. 5. Conservation of the biodiversity in Australia's wet ⁄dry tropics may depend on conserving the natural variation in hydrological connectivity and the unregulated flow of floodplain rivers. Yes Yes

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    • "This is also the case for sessile organisms, in particular rooted or attached plants (Bornette et al. 1994; Holzel and Otte 2001; Bornette and Arens 2002; Leyer 2006; Dos Santos and Thomaz 2007), and for organisms that do not require hydrological connection to move between aquatic habitat patches (e.g. turtles, frogs and some macroinvertebrates) (Morand and Joly 1995; Tockner et al. 1998; Leigh and Sheldon 2009). "
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    ABSTRACT: Hydrological connections between river channels and their adjacent floodplains facilitate the flux of organisms and nutrients and access to increased habitat and new resources. Hydrological connections also deliver water subsidy and potentially disturb (through hydraulic forces) floodplain ecosystems. This study investigates the role of hydrological connectivity as a driver of patterns in wetland plant assemblages in billabongs on the floodplain of an Australian dryland river, exploring indirectly the relative importance of the mechanisms of flux, subsidy and disturbance. Wetland plants were surveyed in billabongs across gradients of hydrological connectivity and depth. Surveys were accompanied by experiments examining germination from the soil seed banks of each site under submerged and waterlogged conditions. The patterns in extant and germinant plant communities in relation to connectivity and depth gradients were used to infer the relative importance of the connectivity-related mechanisms of flux, subsidy and hydraulic disturbance in structuring wetland plant communities. Depth influenced both extant and germinating plant communities. Shallow billabongs supported a greater diversity and abundance of plants, and greater numbers and diversity of germinable seeds in the seed bank. Germination of seeds was greater in waterlogged soils than submerged soils. Thus, the main controls of plant abundance in wetlands appear to be availability of waterlogged soil habitat for germination and absence of light limitation for growth. Hydrological connectivity did not influence the abundance of plants or germinable seeds, but did influence species presence-absence in growing vegetation; this effect did not extend to the germinating community. Thus, hydrological connection does not appear to influence wetland vegetation by facilitating the movement of propagules between habitats. Instead, the patterns observed are consistent with hydrological connection providing a cue for germination through the delivery of water, and by modifying hydraulic habitat.
    Full-text · Article · Aug 2015 · Aquatic Sciences
    • "lateral hydrological connectivity; LHC), Gallardo et al. (2009) proposed hydrological descriptors related to river discharge as surrogates for LHC, such as river distance, flood duration, flood magnitude and water-level variability. From a biological point of view, the duration of overbank flow determines how aquatic organisms can exploit floodplain resources (Junk et al., 1989; Leigh & Sheldon, 2009). Lateral connectivity along with the duration of inundation period affects the size of the floodplain, habitat heterogeneity and availability (Bloechl et al., 2010; Gallardo et al., 2014). "
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    ABSTRACT: Lowland riverine floodplains are among the most dynamic and heterogeneous of ecosystems, but many have been extensively modified. Their provision of important habitats provides a key motivation for restoring natural flow regimes (in terms of magnitude, frequency, duration, timing and rate of change of hydrological conditions). Despite general recognition that aquatic insects respond to changes in water availability, there is little agreement about the influence of flow regime components on community structure in floodplains.We analysed a 6-year (2005 and 2007–2011) data set of aquatic insects (Heteroptera and Coleoptera) in a large Danubian floodplain characterised by pronounced hydrological variability. We hypothesised that abundance and assemblage structure would depend on flow regime components. In particular, we predicted that high-flow events in the mainstream and concurrent high-magnitude floods of prolonged duration would have a positive effect on diversity and abundance and that insect assemblages would differ between phases of hydrological connectivity. In addition, we assessed whether the survival of two threatened aquatic insects, Graphoderus bilineatus and Berosus geminus, depends on hydrological connectivity.Abundance and species richness of Heteroptera and Coleoptera increased during years with frequent extremely high flood pulses and prolonged flooding. Multivariate ordination showed subtle relationships between hydrological conditions, hydrological connectivity and insect assemblages with number of days in flood providing the best fit. Spring floods had a more pronounced effect on the assemblages than autumn floods. The time lag between flood occurrence and its apparent effect on aquatic insects was 17–31 days, reflecting insect life cycles.The abundance of G. bilineatus (Coleoptera: Dytiscidae) was affected by mean water level during the month preceding sampling, whereas the abundance of B. geminus (Coleoptera: Hydrophilidae) was related to the occurrence of prolonged high-magnitude floods.The current water regime of the Danube River favours generalist species with high dispersal capacities and broad niches and food resources. Changes in flow management practices could remove the positive influence of floods on aquatic insect communities and lead to losses of threatened species that depend on these river–floodplain habitats. Our results contribute to the understanding necessary for appropriate evaluation and prioritisation of international floodplain conservation efforts.
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    • "Bornette, Amoros & Lamouroux, 1998; Aarts et al., 2004; Lasne, Lek & Lafaille , 2007; Gli nska-Lewczuk, 2009; Leigh & Sheldon, 2009). Lateral connectivity encapsulates an array of processes, such as the intensity and timing of shear stress; nutrient, organic matter and sediment fluxes; and the import and export of propagules and predators, that ultimately drives the structure and function of the biota in floodplain waterbodies (Amoros & Bornette, 1999, 2002; Leigh & Sheldon, 2009; Rooney, Carli & Bayley, 2013). The Rh^ one restoration project (Lamouroux et al., 2015) offers a unique opportunity to test predictions of changes in floodplain communities after restoration of lateral connectivity in a large river. "

    No preview · Article · Jul 2015 · Freshwater Biology
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