Metacommunity patterns across three Neotropical catchments with varying environmental harshness (original) (raw)
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PLOS ONE, 2020
Understanding how assemblages are structured in space and the factors promoting their distributions is one of the main goals in Ecology, however, studies regarding the distribution of organisms at larger scales remain biased towards terrestrial groups. We attempt to understand if the structure of stream fish metacommunities across a Neotropical ecoregion (Upper Paraná-drainage area of 820,000 km 2) are affected by environmental variables, describing natural environmental gradient, anthropogenic impacts and spatial predictors. For this, we obtained 586 sampling points of fish assemblages in the ecoregion and data on environmental and spatial predictors that potentially affect fish assemblages. We calculated the local beta diversity (Local Contribution to Beta Diversity, LCBD) and alpha diversity from the species list, to be used as response variables in the partial regression models, while the anthropogenic impacts, environmental gradient and spatial factors were used as predictors. We found a high total beta diversity for the ecoregion (0.41) where the greatest values for each site sampled were located at the edges of the ecoregion, while richer communities were found more centrally. All sets of predictors explained the LCBD and alpha diversity, but the most important was dispersal variables, followed by the natural environmental gradient and anthropogenic impact. However, we found an increase in the models' prediction power through the shared effect. Results suggest that environmental filters (i.e. environmental variables such as climate, hydrology and anthropogenic impact) and dispersal limitation together shape fish assemblages of the Upper Paraná ecoregion, showing the importance of using multiple sets of predictors to understand the processes structuring biodiversity distribution.
Environmental Biology of Fishes, 2018
The origin and maintenance of biodiversity and the influence of human activities on biodiversity are issues of central interest to scientists as well as policymakers. We conceptualized the integration of metacommunity paradigms across space and time to better understand the community organization of fish under the hydrological control mechanisms of large river floodplains. In our analysis of variation partitioning and functional ecology, patchy dynamics and mass effects represent special cases of speciessorting paradigms generated by neutral processes in certain species, and the relative roles of neutral processes and local adaptations may increase along with the spatio-temporal extent. The effect of flood event timing, floodplain elevation and vegetation cover on species abundance determined the distribution of seasonal patchy heterogeneous habitats. Spatio-temporal structures were observed among patches of the same habitat types across years but within habitat patches in the same year. The convergence of life history traits and respiratory modes of species associated with different habitat types was not significant, and traits could present overall seasonality within patches and segregation among patches of the same habitat types across years. Furthermore, the similarity of these traits was explained by phylogenetic relationships. At the spatio-temporal scale of the present study, the origin of lineage-specific allometric effects in fish, the origin of habitat specialization and their consequences for metacommunity dynamics were not clear. These results are most likely related to species-sorting processes, in which the species adapted to a specific type of habitat ex situ subsequently colonized an area after it was altered via human activities.
Authorea (Authorea), 2022
The Species-Sorting concept, one of the models developed to explain patterns in metacommunity structure, suggests that relationships between biological communities and environmental conditions is the basic means of the species selection processes. A second concept is Neutral Theory, and the idea of neutral dynamics underpinning metacommunity structure, cannot be overlooked. The third mechanism is the Mass-Effect concept, that focuses on the interaction between environmental condition and neutral effects. In the present study, we partitioned fish communities in streams between niche and neutral theory concepts, identifying the best representation of metacommunity structure, and assessed if linear and hydrographic distance were equivalent in the representation of neutral processes. The result points to the importance of species sorting mechanisms in structuring fish communities with neutral processes best represented by the linear distances. These results are important for the fish fauna conservation leading to three considerations: (i) the variation of the landscape and habitat is important for the stream fish, (ii) the natural barriers are an important landscape component to be considered, and (iii) the artificial barriers (dams and impoundments) need to be planned taking in account the catchment basin as the landscape unit.
The Species Sorting concept, one of the models developed to explain patterns in metacommunity structure, suggests that relationships between biological communities and environmental conditions is the basic means of the species selection processes. A second concept is neutral theory, and the idea of neutral dynamics underpinning metacommunity structure, cannot be overlooked. The third mechanism is the Mass Effect concept, that focuses on the interaction between environmental condition and neutral effects. In the present study, we partitioned fish communities in streams between niche and neutral theory concepts, identifying the best representation of metacommunity structure, and assessed if linear and hydrographic distance were equivalent in the representation of neutral processes. The result points to the importance of species sorting mechanisms in structuring fish communities with neutral processes best represented by the linear distances. On the other hand, the best representation of species' niches was achieved with average values and variance of the local conditions.
PLoS ONE, 2014
Recently, community ecologists are focusing on the relative importance of local environmental factors and proxies to dispersal limitation to explain spatial variation in community structure. Albeit less explored, temporal processes may also be important in explaining species composition variation in metacommunities occupying dynamic systems. We aimed to evaluate the relative role of environmental, spatial and temporal variables on the metacommunity structure of different organism groups in the Upper Paraná River floodplain (Brazil). We used data on macrophytes, fish, benthic macroinvertebrates, zooplankton, periphyton, and phytoplankton collected in up to 36 habitats during a total of eight sampling campaigns over two years. According to variation partitioning results, the importance of predictors varied among biological groups. Spatial predictors were particularly important for organisms with comparatively lower dispersal ability, such as aquatic macrophytes and fish. On the other hand, environmental predictors were particularly important for organisms with high dispersal ability, such as microalgae, indicating the importance of species sorting processes in shaping the community structure of these organisms. The importance of watercourse distances increased when spatial variables were the main predictors of metacommunity structure. The contribution of temporal predictors was low. Our results emphasize the strength of a trait-based analysis and of better defining spatial variables. More importantly, they supported the view that ''all-or-nothing'' interpretations on the mechanisms structuring metacommunities are rather the exception than the rule.
Under the ongoing climate change, understanding the mechanisms structuring the spatial distribution of aquatic species in glacial stream networks is of critical importance to predict the response of aquatic biodiversity in the face of glacier melting. In this study, we propose to use metacommunity theory as a conceptual framework to better understand how river network structure influences the spatial organization of aquatic communities in glacierized catchments. At 51 stream sites in an Andean glacierized catchment (Ecuador), we sampled benthic macroinvertebrates, measured physico-chemical and food resource conditions, and calculated geographical, altitudinal and glaciality distances among all sites. Using partial redundancy analysis, we partitioned community variation to evaluate the relative strength of environmental conditions (e.g., glaciality, food resource) vs. spatial processes (e.g., overland, watercourse, and downstream directional dispersal) in organizing the aquatic metacommunity. Results revealed that both environmental and spatial variables significantly explained community variation among sites. Among all environmental variables, the glacial influence component best explained community variation. Overland spatial variables based on geographical and altitudinal distances significantly affected community variation. Watercourse spatial variables based on glaciality distances had a unique significant effect on community variation. Within alpine catchment, glacial meltwater affects macroinvertebrate metacommunity structure in many ways. Indeed, the harsh environmental conditions characterizing glacial influence not only constitute the primary environmental filter but also, limit water-borne macroinvertebrate dispersal. Therefore, glacier runoff acts as an aquatic dispersal barrier, isolating species in headwater streams, and preventing non-adapted species to colonize throughout the entire stream network. Under a scenario of glacier runoff decrease, we expect a reduction in both environmental filtering and dispersal limitation, inducing a taxonomic homogenization of the aquatic fauna in glacierized catchments as well as the extinction of specialized species in headwater groundwater and glacier-fed streams, and consequently an irreversible reduction in regional diversity.
Hydrobiologia, 2014
Most studies characterize metacommunities based on a single snapshot of the spatial structure, which may be inadequate for taxa with high migratory behavior (e.g., fish). Here, we applied elements of metacommunity structure to examine variations in the spatial distributions of stream fishes over time and to explore possible structuring mechanisms. Although the major environmental gradients influencing species distributions remained largely the same in time, the best-fit pattern of metacommunity structure varied according to sampling occasion and whether or not we included non-native species in the analyses. Quasi-Clementsian and Clementsian structures were the predominant best-fit structures, indicating the importance of species turnover among sites and the existence of more or less discrete community boundaries. The environmental gradient most correlated with metacommunity structure was defined by altitude, area of artificial ponds in the catchment, and dissolved oxygen content. Our results suggest that the best-fit metacommunity structure of the native species can change in time in this catchment due to seasonal changes in distribution patterns. However, the distribution of non-native species throughout the landscape homogenizes the temporal variability in metacommunity structure of native species. Further studies are necessary from other regions to examine best-fit metacommunity structures of stream fishes within relatively short environmental gradients.
1. Metacommunity ecology addresses the situation where sets of local communities are connected by the dispersal of a number of potentially interacting species. Aquatic systems (e.g. lentic versus lotic versus marine) differ from each other in connectivity and environmental heterogeneity, suggesting that metacommunity organisation also differs between major aquatic systems. Here, we review findings from observational field studies on metacommunity organisation in aquatic systems. 2. Species sorting (i.e. species are 'filtered' by environmental factors and occur only at environmentally suitable sites) prevails in aquatic systems, particularly in streams and lakes, but the degree to which dispersal limitation interacts with such environmental control varies among different systems and spatial scales. For example, mainstem rivers and marine coastal systems may be strongly affected by 'mass effects' (i.e. where high dispersal rates homogenise communities to some degree at neighbouring localities, irrespective of their abiotic and biotic environmental conditions), whereas isolated lakes and ponds may be structured by dispersal limitation (i.e. some species do not occur at otherwise-suitable localities simply because sites with potential colonists are too far away). Flow directionality in running waters also differs from water movements in other systems, and this difference may also have effects on the role of dispersal in different aquatic systems. 3. Dispersal limitation typically increases with increasing spatial distance between sites, mass effects potentially increase in importance with decreasing distance between sites, and the dispersal ability of organisms may determine the spatial extents at which species sorting and dispersal processes are most important. 4. A better understanding of the relative roles of species sorting, mass effects and dispersal limitation in affecting aquatic metacommunities requires the following: (i) characterising dispersal rates more directly or adopting better proxies than have been used previously; (ii) considering the nature of aquatic networks; (iii) combining correlative and experimental approaches; (iv) exploring temporal aspects of metacommunity organisation and (v) applying past approaches and statistical methods innovatively for increasing our understanding of metacommunity organisation.
Freshwater Biology, 2012
1. Quantifying the relative importance of environmental filtering versus regional spatial structuring has become an intensively studied area in the context of metacommunity ecology. However, most studies have evaluated the role of environmental and spatial processes using taxonomic data sets of single snapshot surveys. 2. Here, we examined temporal changes in patterns and possible processes behind the functional metacommunity organization of stream fishes in a human-modified landscape. Specifically, we (i) studied general changes in the functional composition of fish assemblages among 40 wadeable stream sites during a 3-year study period in the catchment area of Lake Balaton, Hungary, (ii) quantified the relative importance of spatial and environmental factors as determinants of metacommunity structure and (iii) examined temporal variability in the relative role of spatial and environmental processes for this metacommunity. 3. Partial triadic analysis showed that assemblages could be effectively ordered along a functional gradient from invertebrate consuming species dominated by the opportunistic life-history strategy, to assemblages with a diverse array of functional attributes. The analysis also revealed that functional fish assemblage structure was moderately stable among the sites between the sampling periods. 4. Despite moderate stability, variance partitioning using redundancy analyses (RDA) showed considerable temporal variability in the contribution of environmental and spatial factors to this pattern. The analyses also showed that environmental variables were, in general, more important than spatial ones in determining metacommunity structure. Of these, natural environmental variables (e.g. altitude, velocity) proved to be more influential than human-related effects (e.g. pond area, % inhabited area above the site, nutrient enrichment), even in this landscape with relatively low variation in altitude and stream size. 5. Pond area was, however, the most important human stressor variable that was positively associated with the abundance of non-native species with diverse functional attributes. The temporal variability in the relative importance of environmental and spatial factors was probably shaped by the release of non-native fish from fish ponds to the stream system during flood events. 6. To conclude, both spatial processes and environmental control shape the functional metacommunity organization of stream fish assemblages in human-modified landscapes, but their importance can vary in time. We argue, therefore, that metacommunity studies should better consider temporal variability in the ecological mechanisms (e.g. dispersal limitation, species sorting) that determine the dynamics of landscape-level community organization.
An important aspect of conservation is to understand the founding elements and characteristics of metacommunities in natural environments, and the consequences of anthropogenic disturbance on these patterns. In natural Amazonian environments, the interfluves of the major rivers play an important role in the formation of areas of endemism through the historical isolation of species and the speciation process. We evaluated elements of metacommunity structure for Zygoptera (Insecta: Odonata) sampled in 93 Amazonian streams distributed in two distinct biogeographic regions (areas of endemism). Of sampled streams, 43 were considered to have experienced negligible anthropogenic impacts, and 50 were considered impacted by anthropogenic activities. Our hypothesis was that preserved ("negligible impact") streams would present a Clementsian pattern, forming clusters of distinct species, reflecting the biogeographic pattern of the two regions, and that anthropogenic streams would present random patterns of metacommunity, due to the loss of more sensitive species and dominance of more tolerant species, which have higher dispersal ability and environmental tolerance. In negligible impact streams, the Clementsian pattern reflected a strong biogeographic pattern, which we discuss considering the areas of endemism of Amazonian rivers. As for communities in human-impacted streams, a biotic homogenization was evident, in which rare species were suppressed and the most common species had become hyper-dominant. Understanding the mechanisms that trigger changes in metacommunities is an important issue for conservation, because they can help create mitigation measures for the impacts of anthropogenic activities on biological communities, and so should be expanded to studies using other taxonomic groups in both tropical and temperate systems, and, wherever possible, at multiple spatial scales.