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1.
Historical biogeography studies have at their disposal a small suite of vicariance models to explain genetic differentiation within and between species. One of these processes involves the role of river catchments and their associated watersheds, in driving diversification and is applicable to both aquatic and terrestrial organisms. Although the idea of catchments structuring the genetic history of aquatic organisms is reasonably well understood, their effect on terrestrial organisms has largely been overlooked, with relevant studies being limited in scope. South Africa presents a perfect test-bed for elucidating this mechanism of diversification due to its rich biodiversity, range of climatic environments and many large river catchments. Here we use the cicadas of the Platypleura plumosa complex to highlight the importance of catchments and their associated watersheds in driving diversification of terrestrial invertebrates that lack an aquatic life-stage. Population structure was found to correspond to primary and in some cases secondary catchments; highlighting the need to include information on catchment structure when formulating hypotheses of population diversification. Recognizing that climate change in the near future is likely to alter the environment, and particularly precipitation patterns, insight into recent patterns of population change related to catchments may be useful in a conservation context.  相似文献   

2.
Plastic pollution is distributed across the globe, but compared with marine environments, there is only rudimentary understanding of the distribution and effects of plastics in other ecosystems. Here, we review the transport and effects of plastics across terrestrial, freshwater and marine environments. We focus on hydrological catchments as well‐defined landscape units that provide an integrating scale at which plastic pollution can be investigated and managed. Diverse processes are responsible for the observed ubiquity of plastic pollution, but sources, fluxes and sinks in river catchments are poorly quantified. Early indications are that rivers are hotspots of plastic pollution, supporting some of the highest recorded concentrations. River systems are also likely pivotal conduits for plastic transport among the terrestrial, floodplain, riparian, benthic and transitional ecosystems with which they connect. Although ecological effects of micro‐ and nanoplastics might arise through a variety of physical and chemical mechanisms, consensus and understanding of their nature, severity and scale are restricted. Furthermore, while individual‐level effects are often graphically represented in public media, knowledge of the extent and severity of the impacts of plastic at population, community and ecosystem levels is limited. Given the potential social, ecological and economic consequences, we call for more comprehensive investigations of plastic pollution in ecosystems to guide effective management action and risk assessment. This is reliant on (a) expanding research to quantify sources, sinks, fluxes and fates of plastics in catchments and transitional waters both independently as a major transport routes to marine ecosystems, (b) improving environmentally relevant dose–response relationships for different organisms and effect pathways, (c) scaling up from studies on individual organisms to populations and ecosystems, where individual effects are shown to cause harm and; (d) improving biomonitoring through developing ecologically relevant metrics based on contemporary plastic research.  相似文献   

3.
Effective spatial classification of freshwater biodiversity remains a worldwide conservation challenge. The isolating nature of catchment boundaries over evolutionary timescales makes them potentially important in defining natural units for biodiversity management. We sought to clarify biogeographical relationships amongst drainages within Australia's biodiverse mid‐eastern coastal region (Fitzroy, Burnett, and Mary Catchments) where freshwater communities face considerable urban pressure, using a locally endemic riverine specialist, the white‐throated snapping turtle, Elseya albagula. Mitochondrial and nuclear microsatellite data sets were employed to investigate past and present influences on population connectivity and to identify units for management. Populations within catchments were largely well connected genetically. However, the Fitzroy Catchment contained a distinct genetic lineage, deeply divergent from a second lineage present across the Burnett and Mary Catchments. The two lineages can be considered evolutionarily significant units that reflect historical isolation of the Fitzroy and recent coalescence of the Burnett‐Mary Catchments during lowered Pleistocene sea levels. Congruence with geological evidence and patterns reported for fish and macroinvertebrates supports a shared biogeographical history of a diverse regional biota. This work highlights the need for better spatial classification of freshwater biodiversity at local as well as regional scales, including recognition of potentially cryptic diversity amongst individual river drainages. © 2013 The Linnean Society of London  相似文献   

4.
1. Habitat fragmentation has been implicated as a primary cause for the ongoing erosion of global biodiversity, yet our understanding of the consequences in lotic systems is limited for many species and regions. Because of harsh environmental conditions that select for high colonisation rates, prairie stream fishes may be particularly vulnerable to the effects of fragmentation. Hence, there is urgent need for broader understanding of fragmentation in prairie streams such that meaningful conservation strategies can be developed. Further, examination at large spatial scales, including multiple impoundments and un‐impounded catchments, will help identify the spatial extent of species movement through the landscape. 2. Our study used data from 10 microsatellite loci to describe the genetic structure of creek chub (Semotilus atromaculatus) populations across four catchments (three impounded and one un‐impounded) in the Kansas River basin. We investigated whether genetic diversity was eroded in response to habitat fragmentation imposed by reservoirs and whether intervening lentic habitat increased resistance to dispersal among sites within a catchment. 3. Our analyses revealed that genetic diversity estimates were consistent with large populations regardless of the location of the sampled tributaries, and there was little evidence of recent population reductions. Nevertheless, we found a high degree of spatial genetic structure, suggesting that catchments comprise a set of isolated genetic units and that sample sites within catchments are subdivided into groups largely defined by intervening habitat type. Our data therefore suggest that lentic habitat is a barrier to dispersal among tributaries, thus reducing the opportunity for genetic rescue of populations in tributaries draining into reservoirs. Isolation by a reservoir, however, may not be immediately deleterious if the isolated tributary basin supports a large population.  相似文献   

5.
Restoration and management of riparian ecosystems: a catchment perspective   总被引:10,自引:0,他引:10  
1. We propose that strategies for the management of riparian ecosystems should incorporate concepts of landscape ecology and contemporary principles of restoration and conservation. A detailed understanding of the temporal and spatial dynamics of the catchment landscape (e.g. changes in the connectivity and functions of channel, riparian and terrestrial components) is critical. 2. This perspective is based upon previous definitions of riparian ecosystems, consideration of functional attributes at different spatial scales and retrospective analyses of anthropogenic influences on river catchments. 3. Restoration strategies must derive from a concise definition of the processes to be restored and conserved, recognition of social values and commitments, quantification of ecological circumstances and the quality of background information and determination of alternatives. 4. The basic components of an effective restoration project include: clear objectives (ecological and physical), baseline data and historical information (e.g. the hydrogeomorphic setting and the disturbance regime), a project design that recognizes functional attributes of biotic refugia, a comparison of plans and outcomes with reference ecosystems; a commitment to long-term planning, implementation and monitoring and, finally, a willingness to learn from both successes and failures. 5. Particularly important is a thorough understanding of past natural disturbances and human-induced changes on riparian functions and attributes, obtained by a historical reconstruction of the catchment.  相似文献   

6.
Under discussion are such population groups as management unit (stock) and evolutionarily significant unit, along with the problem of short-term ans long-term goals of conservation activities and wildlife management. The short-term goals may differ from the long-term goals. Management units (stocks) are demographically independent populations, though genetically they may be interconnected to a high degree. It is at this level of population organization that the short-term nature management goals are reached: the preservation of stable reproduction of management units, and the exclusion of excessive pressure on small groups. The evolutionarily significant units have independent conservation status determined by significant reproductive isolation and unique adaptations. It is at this level that long-term management goals are reached: the conservation of the native population structure, the evolutionarily significant differences, the maximum genetic diversity, and, thus, the evolutionary potential.  相似文献   

7.
Effective vegetation classification schemes identify the processes determining species assemblages and support the management of protected areas. They can also provide a framework for ecological research. In the tropics, elevation‐based classifications dominate over alternatives such as river catchments. Given the existence of floristic data for many localities, we ask how useful floristic data are for developing classification schemes in species‐rich tropical landscapes and whether floristic data provide support for classification by river catchment. We analyzed the distribution of vascular plant species within 141 plots across an elevation gradient of 130 to 3200 m asl within La Amistad National Park. We tested the hypothesis that river catchment, combined with elevation, explains much of the variation in species composition. We found that annual mean temperature, elevation, and river catchment variables best explained the variation within local species communities. However, only plots in high‐elevation oak forest and Páramo were distinct from those in low‐ and mid‐elevation zones. Beta diversity did not significantly differ in plots grouped by elevation zones, except for low‐elevation forest, although it did differ between river catchments. None of the analyses identified discrete vegetation assemblages within mid‐elevation (700–2600 m asl) plots. Our analysis supports the hypothesis that river catchment can be an alternative means for classifying tropical forest assemblages in conservation settings.  相似文献   

8.
Subspecific genetic diversity is a source for ongoing evolutionary processes, can be predictive of a population’s ability to respond to conservation challenges, and may represent the raw material for incipient speciation. As such, diagnosable subspecies are increasingly recognized as an important unit for conservation. Differentiating among subspecies can be particularly difficult in ecosystems characterized by recent phenotypic divergence, such as the tidal marshes of North America. These systems require approaches that can capture selective changes which occurred over only a few millennia as species adapted to new habitats following the Holocene glacial retreat. Here we test for genetic differentiation in morphologically distinct tidal-marsh-endemic subspecies of the swamp sparrow (Melospiza georgiana) using nuclear microsatellites. This case study serves as a test approach for the quantification of conservation units for tidal marsh ecosystems. Though prior surveys of mtDNA variation showed no detectable phylogeographic structure, we found evidence of genetic differentiation in seven microsatellite loci between two M. georgiana subspecies. The most likely model of population structure suggested two clusters in western Maryland/Pennsylvania and Delaware/Chesapeake Bays, with a zone of uncertain population assignment in New Jersey. The microsatellite intergrade zone is broader than the known area of morphological intergrades. We show that microsatellites can be used to support a subspecific status for tidal-marsh taxa such as the swamp sparrow, where changing post-glacial environments likely selected for locally adapted traits while neutral genetic structure is weak. This approach thus allows for the identification and conservation of hot spots that foster ongoing evolutionary change.  相似文献   

9.
Restoring streams in an urbanizing world   总被引:1,自引:0,他引:1  
1. The world's population is increasingly urban, and streams and rivers, as the low lying points of the landscape, are especially sensitive to and profoundly impacted by the changes associated with urbanization and suburbanization of catchments. 2. River restoration is an increasingly popular management strategy for improving the physical and ecological conditions of degraded urban streams. In urban catchments, management activities as diverse as stormwater management, bank stabilisation, channel reconfiguration and riparian replanting may be described as river restoration projects. 3. Restoration in urban streams is both more expensive and more difficult than restoration in less densely populated catchments. High property values and finely subdivided land and dense human infrastructure (e.g. roads, sewer lines) limit the spatial extent of urban river restoration options, while stormwaters and the associated sediment and pollutant loads may limit the potential for restoration projects to reverse degradation. 4. To be effective, urban stream restoration efforts must be integrated within broader catchment management strategies. A key scientific and management challenge is to establish criteria for determining when the design options for urban river restoration are so constrained that a return towards reference or pre‐urbanization conditions is not realistic or feasible and when river restoration presents a viable and effective strategy for improving the ecological condition of these degraded ecosystems.  相似文献   

10.
Freshwater ecosystems provide goods and services of critical importance to human societies, yet they are among the most heavily altered ecosystems with an overproportional loss of biodiversity. Major threats to freshwater biodiversity include overexploitation, water pollution, fragmentation, destruction or degradation of habitat, and invasions by non-native species. Alterations of natural flow regimes by man-made dams, land-use changes, river impoundments, and water abstraction often have profound impacts on lotic communities. An understanding of the functional interactions and processes in freshwater ecosystems presents a major challenge for scientists, but is crucial for effective and sustainable restoration. Most conservation approaches to date have considered single species or single level strategies. In contrast, the concept of ‘Integrative Freshwater Ecology and Biodiversity Conservation’ (IFEBC) proposed herein addresses the interactions between abiotic and biotic factors on different levels of organization qualitatively and quantitatively. It consequently results in a more holistic understanding of biodiversity functioning and management. Core questions include modeling of the processes in aquatic key habitats and their functionality based on the identification and quantification of factors which control the spatial and temporal distribution of biodiversity and productivity in aquatic ecosystems. The context and importance of research into IFEBC is illustrated using case studies from three major areas of research: (i) aquatic habitat quality and restoration ecology, (ii) the genetic and evolutionary potential of aquatic species, and (iii) the detection of stress and toxic effects in aquatic ecosystems using biomarkers. In conclusion, our understanding of the functioning of aquatic ecosystems and conservation management can greatly benefit from the methodological combination of molecular and ecological tools.  相似文献   

11.
Aquatic biodiversity faces increasing threats from climate change, escalating exploitation of water and land use intensification. Loss of vegetation in catchments (= watersheds) has been identified as a substantial problem for many river basins, and there is an urgent need to better understand how climate change may interact with changes in catchment vegetation to influence the ecological condition of freshwater ecosystems. We used 20 years of biological monitoring data from Victoria, southeastern Australia, to explore the influences of catchment vegetation and climate on stream macroinvertebrate assemblages. Southeastern Australia experienced a severe drought from 1997 to 2009, with reductions of stream flows >50% in some areas. The prolonged drying substantially altered macroinvertebrate assemblages, with reduced prevalence of many flow‐dependent taxa and increased prevalence of taxa that are tolerant of low‐flow conditions and poor water quality. Stream condition, as assessed by several commonly used macroinvertebrate indices, was consistently better in reaches with extensive native tree cover in upstream catchments. Prolonged drought apparently caused similar absolute declines in macroinvertebrate condition indices regardless of vegetation cover, but streams with intact catchment and riparian vegetation started in better condition and remained so throughout the drought. The largest positive effects of catchment tree cover on both water quality and macroinvertebrate assemblages occurred above a threshold of ca. 60% areal tree cover in upstream catchments and in higher rainfall areas. Riparian tree cover also had positive effects on macroinvertebrate assemblages, especially in warmer catchments. Our results suggest that the benefits of extensive tree cover via improved water quality and in‐channel habitat persist during drought and show the potential for vegetation management to reduce negative impacts of climatic extremes for aquatic ecosystems.  相似文献   

12.
1. Systematic conservation planning is a process widely used in terrestrial and marine environments. A principal goal is to establish a network of protected areas representing the full variety of species or ecosystems. We suggest considering three key attributes of a catchment when planning for aquatic conservation: irreplaceability, condition and vulnerability. 2. Based on observed and modelled distributions of 367 invertebrates in the Australian state of Victoria, conservation value was measured by calculating an irreplaceability coefficient for 1854 subcatchments. Irreplaceability indicates the likelihood of any subcatchment being needed to achieve conservation targets. We estimated it with a bootstrapped heuristic reserve design algorithm, which included upstream–downstream connectivity rules. The selection metric within the algorithm was total summed rarity, corrected for protected area. 3. Condition was estimated using a stressor gradient approach in which two classes of geographical information system Layers were summarised using principal components analysis. The first class was disturbance measures such as nutrient and sediment budgets, salinisation and weed cover. The second class was land use layers, including classes of forestry, agricultural and urban use. The main gradient, explaining 56% of the variation, could be characterised as agricultural disturbance. Seventy‐five per cent of the study area was classified as disturbed. 4. Our definition of vulnerability was the likelihood of a catchment being exposed to a land use that degrades its condition. This was estimated by comparing land capability and current land use. If land was capable of supporting a land use that would have a more degrading effect on a river than its current tenure, it was classified vulnerable (66% of the study area). 79% of catchments contained more then 50% vulnerable land. 5. When integrating the three measures, two major groups of catchments requiring urgent conservation measures were identified. Seven per cent of catchments were highly irreplaceable, highly vulnerable but in degraded condition. These catchments were flagged for restoration. While most highly irreplaceable catchments in good condition were already protected, 2.5% of catchments in this category are on vulnerable land. These are priority areas for assigning river reserves.  相似文献   

13.
A method for spatial freshwater conservation prioritization   总被引:1,自引:0,他引:1  
1. Freshwater ecosystems are amongst the most threatened and poorly protected globally. They continue to be degraded through habitat loss, pollution and invading species and conservation measures are urgently needed to halt declining trends in their biodiversity and integrity.
2. During the past decade a suite of decision support tools and computational approaches have been developed for efficient and targeted conservation action in terrestrial or marine ecosystems. These methods may be poorly suited for planning in freshwater systems because connectivity in terrestrial and marine systems is typically modelled in a way unsuitable for rivers, where connectivity has a strong directional component.
3. We modify the conservation prioritization method and software, zonation , to account for connectivity in a manner better suited to freshwater ecosystems. Prioritization was performed using subcatchment/catchment-based planning units and connectivity was modified to have directional upstream and downstream components consistent with the ecology of our target species.
4. We demonstrate this modified method for rivers and streams in the southern North Island of New Zealand. Data included predicted occupancy from boosted regression tree models of species distributions for 18 fish species. The study area covered 2.1 million hectares and included 394 first- to fourth order catchment or subcatchment planning units.
5. Realistic modelling of connectivity had a major influence on the areas proposed for conservation. If connectivity was ignored, recommended conservation areas were very fragmented. By contrast, when connectivity was modelled, high priority conservation targets consisted of entire river basins or headwater subcatchments.
6. The proposed method serves as a starting point for the implementation of reserve selection methods in river ecosystems.  相似文献   

14.
Habitat fragmentation caused by human activities alters metapopulation dynamics and decreases biological connectivity through reduced migration and gene flow, leading to lowered levels of population genetic diversity and to local extinctions. The threatened Yarra pygmy perch, Nannoperca obscura, is a poor disperser found in small, isolated populations in wetlands and streams of southeastern Australia. Modifications to natural flow regimes in anthropogenically-impacted river systems have recently reduced the amount of habitat for this species and likely further limited its opportunity to disperse. We employed highly resolving microsatellite DNA markers to assess genetic variation, population structure and the spatial scale that dispersal takes place across the distribution of this freshwater fish and used this information to identify conservation units for management. The levels of genetic variation found for N. obscura are amongst the lowest reported for a fish species (mean heterozygosity of 0.318 and mean allelic richness of 1.92). We identified very strong population genetic structure, nil to little evidence of recent migration among demes and a minimum of 11 units for conservation management, hierarchically nested within four major genetic lineages. A combination of spatial analytical methods revealed hierarchical genetic structure corresponding with catchment boundaries and also demonstrated significant isolation by riverine distance. Our findings have implications for the national recovery plan of this species by demonstrating that N. obscura populations should be managed at a catchment level and highlighting the need to restore habitat and avoid further alteration of the natural hydrology.  相似文献   

15.
Norman Owen-Smith 《Oikos》2005,111(3):611-615
Models commonly used in population ecology have somewhat vague and often misleading connections with physical and biological processes connecting organisms with their environments. The metaphysiological modelling approach offers a conceptual framework that is consistent with basic laws and enables integration across levels of organization from cells to ecosystems. This perspective accommodates the intrinsically disequilibrial nature of biological systems in changing environments, as well as adaptive responses to these changes. More attention needs to be paid to factors governing mortality losses rather than the functional or intake response alone. Models need to be based more firmly on underlying biophysical processes in order to serve as reliable guides to conservation action in novel environments.  相似文献   

16.
The fluvial eight-barbel loach Lefua sp. 1 is an undescribed species distributed from the Kinki to Chugoku districts, Honshu, and also on Shikoku Island, Japan. Genetic relationships among local populations are unclear and management units remain undetermined. To aid conservation, we determined genetic population structures from microsatellite loci for 20 populations from three river systems on Honshu. The genetic diversity within populations is relatively low; the majority has experienced genetic bottlenecks. Statistical analysis revealed significant divergence among river systems suggesting that each should be recognized as a management unit. Any conservation program should consider the populations’ genetic uniqueness.  相似文献   

17.
Climate change is expected to exacerbate the current threats to freshwater ecosystems, yet multifaceted studies on the potential impacts of climate change on freshwater biodiversity at scales that inform management planning are lacking. The aim of this study was to fill this void through the development of a novel framework for assessing climate change vulnerability tailored to freshwater ecosystems. The three dimensions of climate change vulnerability are as follows: (i) exposure to climate change, (ii) sensitivity to altered environmental conditions and (iii) resilience potential. Our vulnerability framework includes 1685 freshwater species of plants, fishes, molluscs, odonates, amphibians, crayfish and turtles alongside key features within and between catchments, such as topography and connectivity. Several methodologies were used to combine these dimensions across a variety of future climate change models and scenarios. The resulting indices were overlaid to assess the vulnerability of European freshwater ecosystems at the catchment scale (18 783 catchments). The Balkan Lakes Ohrid and Prespa and Mediterranean islands emerge as most vulnerable to climate change. For the 2030s, we showed a consensus among the applied methods whereby up to 573 lake and river catchments are highly vulnerable to climate change. The anthropogenic disruption of hydrological habitat connectivity by dams is the major factor reducing climate change resilience. A gap analysis demonstrated that the current European protected area network covers <25% of the most vulnerable catchments. Practical steps need to be taken to ensure the persistence of freshwater biodiversity under climate change. Priority should be placed on enhancing stakeholder cooperation at the major basin scale towards preventing further degradation of freshwater ecosystems and maintaining connectivity among catchments. The catchments identified as most vulnerable to climate change provide preliminary targets for development of climate change conservation management and mitigation strategies.  相似文献   

18.
Athalassic wetlands play a pivotal role in sediment and nutrient cycling and retention at the catchment level and are important ecosystems for local and regional biodiversity. Yet, the management of wetlands outside of riverine floodplains (non-riverine wetlands) is difficult, as there is limited understanding of these water bodies and of the processes that threaten them, like secondary salinisation. Accordingly, we describe the patterns of variation in wetland salinity and water chemistry across a regional landscape that is threatened by secondary salinisation. Spatial analyses indicated the distribution of the study wetlands was non-random and there was considerable positive spatial auto-correlation in water chemistry among wetlands—indicating a lack of independence. We detected massive variation in water chemistry among wetlands compared to minimal within-wetland variation and conductivity accounted for most of the among-wetland variation confirming its prominence in non-riverine wetland water chemistry. Wetland salinities were classified by their chemical evaporative pathway and we found a number of wetlands that may have become secondary salinised. The results reported here support the notion that the study, conservation and management of non-riverine wetlands should include assessments made at multiple spatial scales from individual waterbodies through to catchments. This is important because wetlands may not be independent units, but components of larger systems. However, we also note that the use of individual wetlands as units of replication may be problematic under some circumstances. We also argue that the identification of secondarily salinised wetlands will often require a multiple lines of evidence approach.  相似文献   

19.
Both gradual and extreme weather changes trigger complex ecological responses in river ecosystems. It is still unclear to what extent trend or event effects alter biodiversity and functioning in river ecosystems, adding considerable uncertainty to predictions of their future dynamics. Using a comprehensive database of 71 published studies, we show that event – but not trend – effects associated with extreme changes in water flow and temperature substantially reduce species richness. Furthermore, event effects – particularly those affecting hydrological dynamics – on biodiversity and primary productivity were twice as high as impacts due to gradual changes. The synthesis of the available evidence reveals that event effects induce regime shifts in river ecosystems, particularly affecting organisms such as invertebrates. Among extreme weather events, dryness associated with flow interruption caused the largest effects on biota and ecosystem functions in rivers. Effects on ecosystem functions (primary production, organic matter decomposition and respiration) were asymmetric, with only primary production exhibiting a negative response to extreme weather events. Our meta-analysis highlights the disproportionate impact of event effects on river biodiversity and ecosystem functions, with implications for the long-term conservation and management of river ecosystems. However, few studies were available from tropical areas, and our conclusions therefore remain largely limited to temperate river systems. Further efforts need to be directed to assemble evidence of extreme events on river biodiversity and functioning.  相似文献   

20.
River ecosystems face growing threats from human-induced stressors, resulting in habitat degradation and biodiversity loss. Crucial to these ecosystems, macroinvertebrates maintain river health and functioning. In this review, we examine the challenges confronting macroinvertebrates, explore restoration strategies and management approaches, and shed light on knowledge gaps and future research directions. Habitat degradation, water pollution, climate change, and invasive species are discussed as key challenges. Various restoration strategies, such as in-stream habitat restoration, flow regime restoration, riparian zone restoration, and connectivity restoration, are evaluated for macroinvertebrate conservation. Integrated catchment management, adaptive management, community-based management, monitoring, and policy integration are highlighted as essential management approaches, and knowledge gaps in long-term monitoring, innovative restoration techniques, climate change resilience, and policy incorporation are identified as areas calling for further research. Ultimately, a proactive, adaptable, and cooperative approach to river management will ensure macroinvertebrate conservation and sustainable river ecosystems.  相似文献   

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