Lateral hydrological connectivity differentially affects the community characteristics of multiple groups of aquatic invertebrates in tropical wetland pans in South Africa

Abstract

River–floodplain connectivity (i.e. lateral hydrological connectivity, LHC) can directly affect the community characteristics by promoting dispersal of organisms but can also have profound indirect effects by altering local habitat characteristics. A major challenge is to disentangle the relative importance of direct and indirect effects of LHC on organisms. Combining taxonomic data with trait information allows a more mechanistic understanding of how LHC affect biotic communities in floodplains. Here, we attempted to determine the relative importance of the direct and indirect effects of LHC on local environmental variables and community characteristics (taxonomic and trait composition) of three different taxonomic organism groups in a set of 33 temporary floodplain pans along a gradient of LHC. In addition, we specifically aimed to unravel the underlying mechanisms shaping patterns of taxonomic diversity by partitioning compositional dissimilarity between ponds into components of nestedness and spatial turnover. Variation partitioning revealed that most differences in macroinvertebrate and zooplankton community composition between pans resulted from variation in local environmental variables, particularly macrophyte cover and the presence of fish. For large branchiopod crustaceans, however, partitioning indicated that LHC did significantly affect both taxonomic and trait community composition, and reduced local taxon diversity. Partitioning taxonomic and trait β‐diversity showed that community dissimilarity between pans was largely determined by turnover, rather than by nestedness. Overall, our study revealed that the effects of LHC on aquatic invertebrate communities act mainly indirectly by altering local environmental conditions. Although the effects of LHC were significant, they were small compared to those of environmental variables. Our results from the partitioning of taxonomic and trait β‐diversity have important implications for biodiversity conservation efforts in the Ndumo region. We demonstrate the need to conserve multiple pans along the LHC gradient to sustain high regional diversity. A common practice in the study area mainly focuses on the conservation of river‐connected or larger pans.

Regional Scale Risk to the Ecological Sustainability and Ecosystem Services of an African Floodplain System

“…Then from the mid‐1990s, the increase in local human population has resulted in an increase in demand for ecosystem services (Coetzee, Nell, Van Eeden, & De Crom, 2015; Lankford et al., 2010; Smit et al., 2016). This study focuses on the area of the Phongolo floodplain downstream of the Pongolapoort Dam that is characterized by the presence of about 90 depressions or floodplain pans that cover an estimated 20% of the surface area of the floodplain (Heeg & Breen, 1994; Dube et al, 2019). This combination of riverine and pan ecosystems has resulted in a rich biodiversity that represents a unique ecosystem in southern Africa.…”

Impact of Short‐Term Hydrological Components on Landscape Pattern of Waterbird Habitat in Floodplain Wetlands

“…Field monitoring, remote sensing, and numerical modeling are widely applied to obtain hydrological components in wetlands (Dube et al., 2019; Yu et al., 2020; X. Zhang et al., 2021). Field monitoring is only appropriate for obtaining small‐scale and short‐term hydrological components because they are time consuming and labor intensive, and sometimes sites can be inaccessible.…”

“…Field monitoring, remote sensing, and numerical modeling are widely applied to obtain hydrological components in wetlands (Dube et al, 2019;Yu et al, 2020;X. Zhang et al, 2021).…”

Feeding ecology and coexistence dynamics in a community of fishes in a temperate temporary water body

“…The biota present in these extreme environments exhibit a gradient of residency time and reliance on temporal water bodies, with some organisms able to remain their entire life and other only exploiting environments for a portion of their life cycle in this environment, or only for a part of it as an evolutionary consequence (Duble et al, 2019; Meester et al, 2005). The organisms that complete their life cycles in these ecosystems, despite the contrasting seasonal changes, do so thanks to a set of life‐history traits expressed differentially during their different life stages as a result of their inability to leave these sites during the phases with deleterious conditions (Furness, 2015; Schneider & Frost, 1996).…”

“…In North American seasonal water bodies, only the annual killifish Millerichthys robustus (Miller & Hubbs, 1974) has been reported, distributed in temporary water bodies of southeastern Mexico (Domínguez‐Castanedo et al, 2013). In this region, temporary pools usually have long periods of flooding, in which two phases of ecological interactions can be distinguished: (i) the initial months in which M. robustus interacts only with autochthonous species adapted to the annual life cycle (including intraspecific interactions between groups of fish of different ages, as a result of asynchronous hatching waves) and (ii) the subsequent months where there is colonisation of multiple allochthonous species originating from permanent streams (Duble et al, 2019). Based on the above, the aim of this research was to analyse the feeding ecology of fishes in a temporary water body in Veracruz, Mexico, throughout a flooding phase, in order to understand the dynamics of the feeding habits and the effect of coexistence on feeding ecological interactions and on the niche breadth and overlap.…”