Abstract Spatial complexity in metacommunities can be separated into 3 main components: size (i.e., number of habitat patches), spatial arrangement of habitat patches (network topology), and diversity of habitat patch types. Much attention has been paid to lattice-type networks, such as patch-based metapopulations, but interest in understanding ecological networks of alternative geometries is building. Dendritic ecological networks (DENs) include some increasingly threatened ecological systems, such as caves and streams. The restrictive architecture of dendritic ecological networks might have overriding implications for species persistence. I used a modeling approach to investigate how number and spatial arrangement of habitat patches influence metapopulation extinction risk in 2 DENs of different size and topology. Metapopulation persistence was higher in larger networks, but this relationship was mediated by network topology and the dispersal pathways used to navigate the network. Larger networks, especially those with greater topological complexity, generally had lower extinction risk than smaller and less-complex networks, but dispersal bias and magnitude affected the shape of this relationship. Applying these general results to real systems will require empirical data on the movement behavior of organisms and will improve our understanding of the implications of network complexity on population and community patterns and processes.
{"title":"Structural complexity, movement bias, and metapopulation extinction risk in dendritic ecological networks","authors":"E. C. Campbell Grant","doi":"10.1899/09-120.1","DOIUrl":"https://doi.org/10.1899/09-120.1","url":null,"abstract":"Abstract Spatial complexity in metacommunities can be separated into 3 main components: size (i.e., number of habitat patches), spatial arrangement of habitat patches (network topology), and diversity of habitat patch types. Much attention has been paid to lattice-type networks, such as patch-based metapopulations, but interest in understanding ecological networks of alternative geometries is building. Dendritic ecological networks (DENs) include some increasingly threatened ecological systems, such as caves and streams. The restrictive architecture of dendritic ecological networks might have overriding implications for species persistence. I used a modeling approach to investigate how number and spatial arrangement of habitat patches influence metapopulation extinction risk in 2 DENs of different size and topology. Metapopulation persistence was higher in larger networks, but this relationship was mediated by network topology and the dispersal pathways used to navigate the network. Larger networks, especially those with greater topological complexity, generally had lower extinction risk than smaller and less-complex networks, but dispersal bias and magnitude affected the shape of this relationship. Applying these general results to real systems will require empirical data on the movement behavior of organisms and will improve our understanding of the implications of network complexity on population and community patterns and processes.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"30 1","pages":"252 - 258"},"PeriodicalIF":0.0,"publicationDate":"2011-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1899/09-120.1","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"68114873","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract If organisms move beyond the boundaries of local sampling units, regional metacommunity dynamics could undermine the ability of bioassessment studies to characterize local environmental quality. We tested the prediction that fish dispersal influences local fish community structure and bioassessment metrics as a function of site position within stream networks. We evaluated fish community data from the US Environmental Protection Agency's Regional Environmental Monitoring and Assessment Program in West Virginia, USA, to compare the influences of stream network position, ecoregion, basin, and stream size on local fish community composition. We assigned sites to 1 of 3 stream network positions: 1) main channels (MC, n = 12) encompassed streams with upstream catchment areas >200 km2, 2) mainstem tributaries (MT, n = 43) flowed into MC-sized confluences within 15 fluvial km, 3) headwater tributaries (HT, n = 31) lacked such riverine confluences within 15 fluvial km. MT and HT sites had similar upstream catchment sizes and landuse gradients, but species richness was greater in MT sites than HT sites, whereas MT and MC sites were not different in this regard. Three bioassessment metrics were greater in MT sites than HT sites (intolerant species richness, cyprinid species richness, benthic species richness), but a multimetric index of biotic integrity did not differ among stream network positions. Ordinations revealed that fish community composition was organized primarily by zoogeographic basin (Monongahela River basin, New River basin, Ohio River basin), ecoregion (Central Appalachian Plateau, Western Appalachian Plateau, Ridge and Valley), and stream size. Riverine specialists were more abundant in MT than HT sites and were more abundant in basins connected to the Ohio River than in basins isolated from the Ohio River by a large waterfall (New River). Our results suggest that contemporary dispersal among streams influences fish community composition over small spatial scales (101 km), historical dispersal constrained by zoogeographic barriers influences community structure over larger areas (102 km), and contemporary dispersal by fishes influences certain metrics commonly used in bioassessment programs.
如果生物超越了当地采样单元的界限，区域元群落动态可能会破坏生物评价研究表征当地环境质量的能力。我们测试了鱼类扩散影响当地鱼类群落结构和生物评价指标的预测，作为河流网络中站点位置的函数。我们评估了美国环境保护署在美国西弗吉尼亚州的区域环境监测和评估项目的鱼类群落数据，比较了河流网络位置、生态区域、流域和河流大小对当地鱼类群落组成的影响。我们对3个河流网络位置中的1个进行了选址:1)主河道(MC, n = 12)包含上游集水区>200 km2的河流，2)主支流(MT, n = 43)在15 km以内流入MC大小的汇合处，3)源流支流(HT, n = 31)在15 km以内缺乏这样的河流汇合处。在上游流域大小和土地利用梯度上，湿地和湿地相似，但湿地的物种丰富度高于湿地，而湿地和湿地在这方面没有差异。MT站点的3个生物评价指标(不耐物种丰富度、鲤科物种丰富度、底栖物种丰富度)高于HT站点，但生物完整性的多度量指标在河流网络位置之间没有差异。鱼类群落组成主要由动物地理流域(Monongahela河流域、新河流域、俄亥俄河流域)、生态区域(阿巴拉契亚高原中部、西部、山脊和山谷)和河流大小组成。河流专家在MT站点比HT站点更丰富，在与俄亥俄河相连的流域比在与俄亥俄河隔离的大瀑布(新河)流域更丰富。我们的研究结果表明，河流之间的当代扩散影响了小空间尺度(101公里)内鱼类群落的组成，受动物地理屏障限制的历史扩散影响了大范围(102公里)内的群落结构，鱼类的当代扩散影响了生物评估程序中常用的某些指标。
{"title":"Fish community and bioassessment responses to stream network position","authors":"N. Hitt, P. Angermeier","doi":"10.1899/09-155.1","DOIUrl":"https://doi.org/10.1899/09-155.1","url":null,"abstract":"Abstract If organisms move beyond the boundaries of local sampling units, regional metacommunity dynamics could undermine the ability of bioassessment studies to characterize local environmental quality. We tested the prediction that fish dispersal influences local fish community structure and bioassessment metrics as a function of site position within stream networks. We evaluated fish community data from the US Environmental Protection Agency's Regional Environmental Monitoring and Assessment Program in West Virginia, USA, to compare the influences of stream network position, ecoregion, basin, and stream size on local fish community composition. We assigned sites to 1 of 3 stream network positions: 1) main channels (MC, n = 12) encompassed streams with upstream catchment areas >200 km2, 2) mainstem tributaries (MT, n = 43) flowed into MC-sized confluences within 15 fluvial km, 3) headwater tributaries (HT, n = 31) lacked such riverine confluences within 15 fluvial km. MT and HT sites had similar upstream catchment sizes and landuse gradients, but species richness was greater in MT sites than HT sites, whereas MT and MC sites were not different in this regard. Three bioassessment metrics were greater in MT sites than HT sites (intolerant species richness, cyprinid species richness, benthic species richness), but a multimetric index of biotic integrity did not differ among stream network positions. Ordinations revealed that fish community composition was organized primarily by zoogeographic basin (Monongahela River basin, New River basin, Ohio River basin), ecoregion (Central Appalachian Plateau, Western Appalachian Plateau, Ridge and Valley), and stream size. Riverine specialists were more abundant in MT than HT sites and were more abundant in basins connected to the Ohio River than in basins isolated from the Ohio River by a large waterfall (New River). Our results suggest that contemporary dispersal among streams influences fish community composition over small spatial scales (101 km), historical dispersal constrained by zoogeographic barriers influences community structure over larger areas (102 km), and contemporary dispersal by fishes influences certain metrics commonly used in bioassessment programs.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"367 1","pages":"296 - 309"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84915358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Brown, C. Swan, D. Auerbach, E. C. Campbell Grant, N. Hitt, K. Maloney, C. Patrick
Abstract Explaining the mechanisms underlying patterns of species diversity and composition in riverine networks is challenging. Historically, community ecologists have conceived of communities as largely isolated entities and have focused on local environmental factors and interspecific interactions as the major forces determining species composition. However, stream ecologists have long embraced a multiscale approach to studying riverine ecosystems and have studied both local factors and larger-scale regional factors, such as dispersal and disturbance. River networks exhibit a dendritic spatial structure that can constrain aquatic organisms when their dispersal is influenced by or confined to the river network. We contend that the principles of metacommunity theory would help stream ecologists to understand how the complex spatial structure of river networks mediates the relative influences of local and regional control on species composition. From a basic ecological perspective, the concept is attractive because new evidence suggests that the importance of regional processes (dispersal) depends on spatial structure of habitat and on connection to the regional species pool. The role of local factors relative to regional factors will vary with spatial position in a river network. From an applied perspective, the long-standing view in ecology that local community composition is an indicator of habitat quality may not be uniformly applicable across a river network, but the strength of such bioassessment approaches probably will depend on spatial position in the network. The principles of metacommunity theory are broadly applicable across taxa and systems but seem of particular consequence to stream ecology given the unique spatial structure of riverine systems. By explicitly embracing processes at multiple spatial scales, metacommunity theory provides a foundation on which to build a richer understanding of stream communities.
{"title":"Metacommunity theory as a multispecies, multiscale framework for studying the influence of river network structure on riverine communities and ecosystems","authors":"B. Brown, C. Swan, D. Auerbach, E. C. Campbell Grant, N. Hitt, K. Maloney, C. Patrick","doi":"10.1899/10-129.1","DOIUrl":"https://doi.org/10.1899/10-129.1","url":null,"abstract":"Abstract Explaining the mechanisms underlying patterns of species diversity and composition in riverine networks is challenging. Historically, community ecologists have conceived of communities as largely isolated entities and have focused on local environmental factors and interspecific interactions as the major forces determining species composition. However, stream ecologists have long embraced a multiscale approach to studying riverine ecosystems and have studied both local factors and larger-scale regional factors, such as dispersal and disturbance. River networks exhibit a dendritic spatial structure that can constrain aquatic organisms when their dispersal is influenced by or confined to the river network. We contend that the principles of metacommunity theory would help stream ecologists to understand how the complex spatial structure of river networks mediates the relative influences of local and regional control on species composition. From a basic ecological perspective, the concept is attractive because new evidence suggests that the importance of regional processes (dispersal) depends on spatial structure of habitat and on connection to the regional species pool. The role of local factors relative to regional factors will vary with spatial position in a river network. From an applied perspective, the long-standing view in ecology that local community composition is an indicator of habitat quality may not be uniformly applicable across a river network, but the strength of such bioassessment approaches probably will depend on spatial position in the network. The principles of metacommunity theory are broadly applicable across taxa and systems but seem of particular consequence to stream ecology given the unique spatial structure of riverine systems. By explicitly embracing processes at multiple spatial scales, metacommunity theory provides a foundation on which to build a richer understanding of stream communities.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"78 1","pages":"310 - 327"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82031481","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The most basic ecological questions are frequently the most difficult to answer. The foundational questions of community ecology are prime examples: Why are these species found in these abundances at this location? Why does the assemblage at site X differ from that at site Y? How and why do these assemblages change through time? The questions are simple, but the answers have proven to be multifaceted, complex, and often elusive. However, community ecologists recently have made large strides in their ability to answer these fundamental questions. Much of this progress has resulted from recognition of a simple principle: processes that influence the structure and dynamics of communities occur on multiple spatial scales and, for many communities, focusing on processes at a single spatial scale will not provide understanding of the factors that shape communities. In particular, recent research has focused on the interaction between local and regional forces in structuring communities, where local refers to species interactions and environmental filtering, whereas regional refers to processes primarily driven by the dispersal of organisms. Community ecologists have long realized that both local and regional processes can structure communities, but the recent emphasis on the interactions between scales has led to progress in both theoretical and empirical community ecology. This change in perspective was implicit in the controversial Neutral Theory (Hubbell 2001), is explicit in the emerging body of theory known as Metacommunity Ecology (Leibold et al. 2004, Holyoak et al. 2005), and continues to produce a groundswell of innovative community ecology research. Embracing the interaction between local and regional factors as an organizing feature of communities has obvious significance for the study of riverine communities and ecosystems. Streams and rivers are, by their nature, spatially structured systems with a very particular dendritic (i.e., linear branching), hierarchical architecture (Fagan 2002, Grant et al. 2007). The directional flow of rivers strongly affects the movement of organisms through bulk flow, which transports both organisms and materials, and the life histories of many organisms reflect evolutionary responses to a flowing-water environment that leads to directional rather than diffusive dispersal patterns. The pervasive and sometimes extensive movement of organisms in riverine landscapes suggests that understanding community assembly and dynamics in riverine systems will require knowledge of regional dispersal-driven processes in addition to knowledge of local environmental conditions and species interactions. The results of recent research support this assertion (Heino 2005, Muneepeerakul et al. 2007, 2008a, b, Heino and Mykra 2008, Hitt and Angermeier 2008, Brown and Swan 2010, Clarke et al. 2010). Within this framework, a rapidly emerging focal point for research is the role of spatial configuration of riverine networks in dictati
最基本的生态问题往往是最难回答的。群落生态学的基本问题就是最好的例子:为什么这些物种在这个地方如此丰富?为什么X点的组合与Y点的不同?这些组合是如何以及为什么随着时间而变化的?问题很简单，但答案却是多方面的、复杂的，而且往往难以捉摸。然而，群落生态学家最近在回答这些基本问题的能力上取得了很大的进步。这一进展很大程度上是由于认识到一个简单的原则:影响社区结构和动态的过程发生在多个空间尺度上，对许多社区来说，侧重于单一空间尺度的过程将无法理解塑造社区的因素。特别是，最近的研究集中在构建群落的局部和区域力量之间的相互作用上，其中局部是指物种相互作用和环境过滤，而区域是指主要由生物扩散驱动的过程。群落生态学家早就认识到，地方和区域过程都可以构建群落，但最近对尺度之间相互作用的重视导致了理论和实证群落生态学的进展。这种观点的变化隐含在有争议的中性理论(Hubbell 2001)中，在被称为元群落生态学的新兴理论体系中是明确的(Leibold et al. 2004, Holyoak et al. 2005)，并继续产生创新群落生态学研究的浪潮。将局地因子与区域因子的相互作用作为群落的组织特征，对河流群落与生态系统的研究具有明显的意义。溪流和河流，就其本质而言，是具有非常特殊的树突(即线性分支)和层次结构的空间结构系统(Fagan 2002, Grant et al. 2007)。河流的定向流动强烈地影响着生物的运动，通过大量流动来运输生物和物质，许多生物的生活史反映了对流动水环境的进化反应，这种环境导致了定向而不是扩散的扩散模式。河流景观中生物的普遍和有时广泛的运动表明，了解河流系统中的群落组合和动态，除了了解当地环境条件和物种相互作用外，还需要了解区域分散驱动过程。最近的研究结果支持这一断言(Heino 2005, Muneepeerakul et al. 2007, 2008a, b, Heino and Mykra 2008, Hitt and Angermeier 2008, Brown and Swan 2010, Clarke et al. 2010)。在这个框架内，一个迅速出现的研究焦点是河流网络的空间配置在决定社区属性方面的作用。河流网络的配置影响了一些生物的占用模式(Grant et al. 2009)，改变了构建河流无脊椎动物群落的地方和区域力量的相对平衡(Brown and Swan 2010)，并影响了生物评估指标的表现(Hitt and Angermeier 2008)。多尺度、多物种的方法来研究树突网络结构对河流群落的影响是这一系列特别文章的主题。在这个特别系列的贡献是结合在一起的认识到需要同时考虑多个空间尺度和关注河流系统的空间结构的影响时，试图解释结构和功能1 E-mail地址:chris.swan@umbc.edu 2 bbrown3@umbc.edu J. N. Am。Benthol。Soc。2011, 30(1): 232-234。by The North American Benthological Society DOI: 10.1899/10-150.1
{"title":"Advancing theory of community assembly in spatially structured environments: local vs regional processes in river networks","authors":"C. Swan, B. Brown","doi":"10.1899/10-150.1","DOIUrl":"https://doi.org/10.1899/10-150.1","url":null,"abstract":"The most basic ecological questions are frequently the most difficult to answer. The foundational questions of community ecology are prime examples: Why are these species found in these abundances at this location? Why does the assemblage at site X differ from that at site Y? How and why do these assemblages change through time? The questions are simple, but the answers have proven to be multifaceted, complex, and often elusive. However, community ecologists recently have made large strides in their ability to answer these fundamental questions. Much of this progress has resulted from recognition of a simple principle: processes that influence the structure and dynamics of communities occur on multiple spatial scales and, for many communities, focusing on processes at a single spatial scale will not provide understanding of the factors that shape communities. In particular, recent research has focused on the interaction between local and regional forces in structuring communities, where local refers to species interactions and environmental filtering, whereas regional refers to processes primarily driven by the dispersal of organisms. Community ecologists have long realized that both local and regional processes can structure communities, but the recent emphasis on the interactions between scales has led to progress in both theoretical and empirical community ecology. This change in perspective was implicit in the controversial Neutral Theory (Hubbell 2001), is explicit in the emerging body of theory known as Metacommunity Ecology (Leibold et al. 2004, Holyoak et al. 2005), and continues to produce a groundswell of innovative community ecology research. Embracing the interaction between local and regional factors as an organizing feature of communities has obvious significance for the study of riverine communities and ecosystems. Streams and rivers are, by their nature, spatially structured systems with a very particular dendritic (i.e., linear branching), hierarchical architecture (Fagan 2002, Grant et al. 2007). The directional flow of rivers strongly affects the movement of organisms through bulk flow, which transports both organisms and materials, and the life histories of many organisms reflect evolutionary responses to a flowing-water environment that leads to directional rather than diffusive dispersal patterns. The pervasive and sometimes extensive movement of organisms in riverine landscapes suggests that understanding community assembly and dynamics in riverine systems will require knowledge of regional dispersal-driven processes in addition to knowledge of local environmental conditions and species interactions. The results of recent research support this assertion (Heino 2005, Muneepeerakul et al. 2007, 2008a, b, Heino and Mykra 2008, Hitt and Angermeier 2008, Brown and Swan 2010, Clarke et al. 2010). Within this framework, a rapidly emerging focal point for research is the role of spatial configuration of riverine networks in dictati","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"62 1","pages":"232 - 234"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86458391","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Understanding the mechanisms that create spatial and temporal patterns of functional diversity in stream networks is a goal of basic research and has implications for effective conservation of freshwater ecosystems. These patterns are likely to be influenced by the combination of temporally variable environmental conditions, movement constraints imposed by network structure, and the trait composition of local communities. We developed a simplified metacommunity model to investigate complex interactions among these factors under lottery competition for local resources, such as establishment sites. We used this model to examine how local and regional community composition varied in 3 scenarios: a null implementation involving only spatial effects, an implementation that combined network constraints with dispersal-trait variation, and an implementation in which a trade-off between multiple functional traits was paired with varying levels of temporal autocorrelation in the intensity of mortality. These simulations clarified the conditions that allow a single functional strategy to exclude others in a dendritic network and demonstrated 2 distinct modes of regional partitioning that can support the persistence of multiple functional strategies within such networks. The results suggested that the emergence of watershed or headwater–outlet partitioning depends on the functional dispersal differences present in the metacommunity and that autocorrelated mortality levels can collapse these regional divisions when they depend on a trade-off between dispersal ability and mortality resistance. We discuss the need to confront the complexity of interacting controls on community composition in rivers and streams and suggest opportunities to move beyond the basic framework we present.
{"title":"Spatiotemporal controls of simulated metacommunity dynamics in dendritic networks","authors":"Daniel A. Auerbach, N. L. Poff","doi":"10.1899/09-126.1","DOIUrl":"https://doi.org/10.1899/09-126.1","url":null,"abstract":"Abstract Understanding the mechanisms that create spatial and temporal patterns of functional diversity in stream networks is a goal of basic research and has implications for effective conservation of freshwater ecosystems. These patterns are likely to be influenced by the combination of temporally variable environmental conditions, movement constraints imposed by network structure, and the trait composition of local communities. We developed a simplified metacommunity model to investigate complex interactions among these factors under lottery competition for local resources, such as establishment sites. We used this model to examine how local and regional community composition varied in 3 scenarios: a null implementation involving only spatial effects, an implementation that combined network constraints with dispersal-trait variation, and an implementation in which a trade-off between multiple functional traits was paired with varying levels of temporal autocorrelation in the intensity of mortality. These simulations clarified the conditions that allow a single functional strategy to exclude others in a dendritic network and demonstrated 2 distinct modes of regional partitioning that can support the persistence of multiple functional strategies within such networks. The results suggested that the emergence of watershed or headwater–outlet partitioning depends on the functional dispersal differences present in the metacommunity and that autocorrelated mortality levels can collapse these regional divisions when they depend on a trade-off between dispersal ability and mortality resistance. We discuss the need to confront the complexity of interacting controls on community composition in rivers and streams and suggest opportunities to move beyond the basic framework we present.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"1 1","pages":"235 - 251"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89279909","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Given the unique spatial structure of stream habitat and the stochasticity characteristic of lotic ecosystems, metacommunity approaches hold much promise in the field of stream ecology. We take advantage of the tight parallels between neutral theories of molecular evolution and community assembly and present a novel conceptual approach to evaluating the role of stochasticity and dispersal limitation in structuring stream metacommunities. The analogous neutral frameworks generate similar expectations for the spatial structure of species comprising communities and genes comprising populations, particularly among patchily distributed, isolated local habitats (e.g., headwater streams) where among-stream dispersal is expected to be limited. Our emphasis is on the conceptual value of this approach, but we also used a limited data set composed of intensively sampled community and population-genetic data collected from 5 to 7 Rocky Mountain alpine streams for illustrative purposes. We characterized neutral population genetic structure as mitochondrial haplotype distributions for the blackfly Prosimulium neomacropyga, which shows strong genetic isolation by distance across the study region. We assessed community structure as the relative frequencies of ecologically similar species in the family Chironomidae collected annually over 2000–2003. Species richness was positively correlated with haplotype richness across streams (r = 0.55), and analogous methods revealed significant &bgr; diversity at both the population-genetic (FST = 0.23) and the community (FST = 0.16) levels. However, a more spatially explicit comparison of pairwise community dissimilarity and genetic distance revealed no evidence of correlation (Mantel test, r = −0.18, p = 0.54), a result suggesting no effect of spatial distance on community similarity at the relatively fine spatial scale of our study. We discuss 2 key arguments to explain the lack of community distance decay: 1) unaccounted environmental differences among streams, and 2) varying spatial and temporal scales of neutral processes (including genetic drift and ecological drift; i.e., stochastic temporal change) between population-genetic and community levels. Evidence for both selective and neutral explanations is compelling in this system. The explanations cannot be disentangled with the current data, but the study has strong heuristic value that we hope will stimulate future efforts in stream metacommunity analysis.
{"title":"Examining spatial concordance of genetic and species diversity patterns to evaluate the role of dispersal limitation in structuring headwater metacommunities","authors":"D. Finn, N. Poff","doi":"10.1899/10-035.1","DOIUrl":"https://doi.org/10.1899/10-035.1","url":null,"abstract":"Abstract Given the unique spatial structure of stream habitat and the stochasticity characteristic of lotic ecosystems, metacommunity approaches hold much promise in the field of stream ecology. We take advantage of the tight parallels between neutral theories of molecular evolution and community assembly and present a novel conceptual approach to evaluating the role of stochasticity and dispersal limitation in structuring stream metacommunities. The analogous neutral frameworks generate similar expectations for the spatial structure of species comprising communities and genes comprising populations, particularly among patchily distributed, isolated local habitats (e.g., headwater streams) where among-stream dispersal is expected to be limited. Our emphasis is on the conceptual value of this approach, but we also used a limited data set composed of intensively sampled community and population-genetic data collected from 5 to 7 Rocky Mountain alpine streams for illustrative purposes. We characterized neutral population genetic structure as mitochondrial haplotype distributions for the blackfly Prosimulium neomacropyga, which shows strong genetic isolation by distance across the study region. We assessed community structure as the relative frequencies of ecologically similar species in the family Chironomidae collected annually over 2000–2003. Species richness was positively correlated with haplotype richness across streams (r = 0.55), and analogous methods revealed significant &bgr; diversity at both the population-genetic (FST = 0.23) and the community (FST = 0.16) levels. However, a more spatially explicit comparison of pairwise community dissimilarity and genetic distance revealed no evidence of correlation (Mantel test, r = −0.18, p = 0.54), a result suggesting no effect of spatial distance on community similarity at the relatively fine spatial scale of our study. We discuss 2 key arguments to explain the lack of community distance decay: 1) unaccounted environmental differences among streams, and 2) varying spatial and temporal scales of neutral processes (including genetic drift and ecological drift; i.e., stochastic temporal change) between population-genetic and community levels. Evidence for both selective and neutral explanations is compelling in this system. The explanations cannot be disentangled with the current data, but the study has strong heuristic value that we hope will stimulate future efforts in stream metacommunity analysis.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"27 1","pages":"273 - 283"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73004934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Measures of species diversity are valuable tools for assessing ecosystem health. However, most assessments have addressed individual sites or regional taxon pools, with few comparisons of differences in assemblage composition within or among regions. We examined the effects of anthropogenic disturbance on local richness (&agr; diversity) and species turnover (&bgr; diversity) of benthic macroinvertebrates in small streams within and between 2 ecoregions (Northern Piedmont vs Southeastern Plains ecoregions) of the Patuxent River basin (Maryland, USA). Regional species pools did not differ between ecoregions (Piedmont = 166 taxa, Plains = 162 taxa); however, local richness was lower in the Plains (mean = 17.4 taxa/stream) compared to the Piedmont (mean = 22.2 taxa/stream). When streams were categorized into disturbance classes (low, medium, high), local richness did not differ among categories for either region. However, at the entire Patuxent scale, local richness tended to decrease with % impervious cover in a watershed. Variation in species composition, analyzed with nonmetric multidimensional scaling (nMDS), differed significantly between Piedmont and Plains streams, and Plains streams had higher &bgr; diversity than Piedmont streams. When partitioned by disturbance category and region, &bgr; diversity differed only between the low-disturbance sites (Plains > Piedmont). Relationships between &bgr; diversity and environmental variables varied by region. &bgr; diversity was weakly negatively related to % row-crop cover in a watershed at the entire Patuxent scale. For the Piedmont region, &bgr; diversity tended to decrease with % forest, % pasture, and % row-crop cover in a watershed. Such negative relationships between &bgr; diversity and landuse variables indicate a possible homogenization of the assemblage. The incongruence between diversity measures and composition measures, together with differing effects of anthropogenic land use on &bgr; diversity in the 2 regions, emphasizes the need to incorporate both &agr; and &bgr; diversity and regional environmental factors in conservation/land management studies.
{"title":"Anthropogenic disturbance and landscape patterns affect diversity patterns of aquatic benthic macroinvertebrates","authors":"K. Maloney, P. Munguia, R. Mitchell","doi":"10.1899/09-112.1","DOIUrl":"https://doi.org/10.1899/09-112.1","url":null,"abstract":"Abstract Measures of species diversity are valuable tools for assessing ecosystem health. However, most assessments have addressed individual sites or regional taxon pools, with few comparisons of differences in assemblage composition within or among regions. We examined the effects of anthropogenic disturbance on local richness (&agr; diversity) and species turnover (&bgr; diversity) of benthic macroinvertebrates in small streams within and between 2 ecoregions (Northern Piedmont vs Southeastern Plains ecoregions) of the Patuxent River basin (Maryland, USA). Regional species pools did not differ between ecoregions (Piedmont = 166 taxa, Plains = 162 taxa); however, local richness was lower in the Plains (mean = 17.4 taxa/stream) compared to the Piedmont (mean = 22.2 taxa/stream). When streams were categorized into disturbance classes (low, medium, high), local richness did not differ among categories for either region. However, at the entire Patuxent scale, local richness tended to decrease with % impervious cover in a watershed. Variation in species composition, analyzed with nonmetric multidimensional scaling (nMDS), differed significantly between Piedmont and Plains streams, and Plains streams had higher &bgr; diversity than Piedmont streams. When partitioned by disturbance category and region, &bgr; diversity differed only between the low-disturbance sites (Plains > Piedmont). Relationships between &bgr; diversity and environmental variables varied by region. &bgr; diversity was weakly negatively related to % row-crop cover in a watershed at the entire Patuxent scale. For the Piedmont region, &bgr; diversity tended to decrease with % forest, % pasture, and % row-crop cover in a watershed. Such negative relationships between &bgr; diversity and landuse variables indicate a possible homogenization of the assemblage. The incongruence between diversity measures and composition measures, together with differing effects of anthropogenic land use on &bgr; diversity in the 2 regions, emphasizes the need to incorporate both &agr; and &bgr; diversity and regional environmental factors in conservation/land management studies.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"9 1","pages":"284 - 295"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75844735","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
E. Pilgrim, S. Jackson, S. Swenson, István Turcsányi, E. Friedman, L. Weigt, M. Bagley
Abstract Taxonomic identification of benthic macroinvertebrates is critical to protocols used to assess the biological integrity of aquatic ecosystems. The time, expense, and inherent error rate of species-level morphological identifications has necessitated use of genus- or family-level identifications in most large, statewide bioassessment programs. Use of coarse-scale taxonomy can obscure signal about biological condition, particularly if the range of species tolerances is large within genera or families. We hypothesized that integration of deoxyribonucleic acid (DNA) barcodes (partial cytochrome c oxidase subunit I sequences) into bioassessment protocols would provide greater discriminatory ability than genus-level identifications and that this increased specificity could lead to more sensitive assessments of water quality and habitat. Analysis of DNA barcodes from larval specimens of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa collected as part of Maryland's Biological Stream Survey (MBSS) revealed ∼2 to 3× as many DNA-barcode groups or molecular operational taxonomic units (mOTUs) as morphologically identified genera. As expected, geographic distributions for several mOTUs were tighter than for the parent genus, but few mOTUs showed closer associations with water-quality variables or physical-habitat features than did the genus in which they belonged. The need for improved protocols for the consistent generation of DNA barcodes is discussed.
{"title":"Incorporation of DNA barcoding into a large-scale biomonitoring program: opportunities and pitfalls","authors":"E. Pilgrim, S. Jackson, S. Swenson, István Turcsányi, E. Friedman, L. Weigt, M. Bagley","doi":"10.1899/10-012.1","DOIUrl":"https://doi.org/10.1899/10-012.1","url":null,"abstract":"Abstract Taxonomic identification of benthic macroinvertebrates is critical to protocols used to assess the biological integrity of aquatic ecosystems. The time, expense, and inherent error rate of species-level morphological identifications has necessitated use of genus- or family-level identifications in most large, statewide bioassessment programs. Use of coarse-scale taxonomy can obscure signal about biological condition, particularly if the range of species tolerances is large within genera or families. We hypothesized that integration of deoxyribonucleic acid (DNA) barcodes (partial cytochrome c oxidase subunit I sequences) into bioassessment protocols would provide greater discriminatory ability than genus-level identifications and that this increased specificity could lead to more sensitive assessments of water quality and habitat. Analysis of DNA barcodes from larval specimens of Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa collected as part of Maryland's Biological Stream Survey (MBSS) revealed ∼2 to 3× as many DNA-barcode groups or molecular operational taxonomic units (mOTUs) as morphologically identified genera. As expected, geographic distributions for several mOTUs were tighter than for the parent genus, but few mOTUs showed closer associations with water-quality variables or physical-habitat features than did the genus in which they belonged. The need for improved protocols for the consistent generation of DNA barcodes is discussed.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"5 1","pages":"217 - 231"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90183133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Dispersal rates and the diversity of the regional species pool strongly affect community assembly in habitat patches. Incorporating these elements mechanistically into a model of community assembly requires adoption of a metacommunity paradigm. We developed a hierarchical model of community assembly for stream insects that incorporates regional effects (distance to and generic richness of other stream reaches) and local effects (water quality and community composition). We tested our model with a unique data set detailing changes in stream-insect community composition over 6 sampling periods across a 27-y period of watershed recovery from anthropogenic effects. &agr; and &ggr; richness increased greatly over the time period, whereas &bgr; richness declined strongly. Generic richness of individual stream reaches was significantly related to dispersal distance and generic richness of surrounding immigrant pools in preceding years. However, the strength of the relationship declined over time indicating that distance to potential colonists played a major role only early in community assembly. Water quality, characterized by an ordination of pH, temperature, conductivity, dissolved O2, NO3, NH4, and orthophosphate, was correlated with generic richness at all time periods during the community-assembly sequence. The functional diversity (diversity of functional attributes present in an assemblage of species) of entire communities was lower than expected from random simulations in all sampling years. However, functional diversity of individual functional feeding groups varied through time and amongst themselves. Our results suggest that both deterministic and random processes are important in metacommunity assembly, and their relative strengths vary throughout the assembly process.
{"title":"Reconstructing the assembly of a stream-insect metacommunity","authors":"C. Patrick, C. Swan","doi":"10.1899/09-169.1","DOIUrl":"https://doi.org/10.1899/09-169.1","url":null,"abstract":"Abstract Dispersal rates and the diversity of the regional species pool strongly affect community assembly in habitat patches. Incorporating these elements mechanistically into a model of community assembly requires adoption of a metacommunity paradigm. We developed a hierarchical model of community assembly for stream insects that incorporates regional effects (distance to and generic richness of other stream reaches) and local effects (water quality and community composition). We tested our model with a unique data set detailing changes in stream-insect community composition over 6 sampling periods across a 27-y period of watershed recovery from anthropogenic effects. &agr; and &ggr; richness increased greatly over the time period, whereas &bgr; richness declined strongly. Generic richness of individual stream reaches was significantly related to dispersal distance and generic richness of surrounding immigrant pools in preceding years. However, the strength of the relationship declined over time indicating that distance to potential colonists played a major role only early in community assembly. Water quality, characterized by an ordination of pH, temperature, conductivity, dissolved O2, NO3, NH4, and orthophosphate, was correlated with generic richness at all time periods during the community-assembly sequence. The functional diversity (diversity of functional attributes present in an assemblage of species) of entire communities was lower than expected from random simulations in all sampling years. However, functional diversity of individual functional feeding groups varied through time and amongst themselves. Our results suggest that both deterministic and random processes are important in metacommunity assembly, and their relative strengths vary throughout the assembly process.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"1 1","pages":"259 - 272"},"PeriodicalIF":0.0,"publicationDate":"2011-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89857313","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abstract Patchiness is hierarchically structured in stream ecosystems and transcends multiple spatial and temporal scales. Regulation of streams through channelization and flow stabilization often homogenizes in-stream habitats, thereby reducing this patchiness. We conducted a patch-disturbance experiment with individual brick substrata in 2 reaches (open vs closed canopy) and 2 seasons (summer vs winter) in a eutrophic regulated stream. Although the stream was regulated, we expected coarse-scale attributes (canopy cover, season) to influence the effects of disturbance at the fine scale of individual bricks. Brick substrata had 3 degrees of structural complexity (low = smooth, intermediate = techno, high = hetero). Replicates of each brick type were physically disturbed at frequencies of every 5 and 10 d or were left undisturbed during each 30-d experimental period. At the end of each experiment, individual bricks were collected, periphyton biomass was estimated, and macroinvertebrates were identified and counted. Natural densities, taxon richness, and assemblage composition of macroinvertebrates differed significantly between sites and seasons. Periphyton biomass was higher in the open-canopy than in the closed-canopy site in both seasons, especially summer. Periphyton biomass differed among brick types at each site and season, but disturbance had no effect on periphyton biomass within a brick type. At the closed-canopy site, undisturbed hetero bricks had higher macroinvertebrate density, richness, and biomass than the other brick types and disturbance treatments in both seasons. At the open-canopy site, no effect of disturbance was found for any brick type in summer, whereas undisturbed and 10-d hetero bricks had higher macroinvertebrate density, richness, and biomass than the other brick types and disturbance treatments in winter. Besides the dominant role of site and season in this study, our results also suggest that substrate patch complexity can be significant in the response of macroinvertebrates to physical disturbance in regulated streams. As in natural systems, coarse-scale attributes of stream reaches, e.g., degree of canopy cover and season, also provide the spatiotemporal hierarchical context in which disturbance effects are realized in regulated streams, thus having major implications for resource managers.
{"title":"Scales of patchiness in the response of lotic macroinvertebrates to disturbance in a regulated river","authors":"C. Robinson, S. Blaser, C. Jolidon, L. Shama","doi":"10.1899/10-051.1","DOIUrl":"https://doi.org/10.1899/10-051.1","url":null,"abstract":"Abstract Patchiness is hierarchically structured in stream ecosystems and transcends multiple spatial and temporal scales. Regulation of streams through channelization and flow stabilization often homogenizes in-stream habitats, thereby reducing this patchiness. We conducted a patch-disturbance experiment with individual brick substrata in 2 reaches (open vs closed canopy) and 2 seasons (summer vs winter) in a eutrophic regulated stream. Although the stream was regulated, we expected coarse-scale attributes (canopy cover, season) to influence the effects of disturbance at the fine scale of individual bricks. Brick substrata had 3 degrees of structural complexity (low = smooth, intermediate = techno, high = hetero). Replicates of each brick type were physically disturbed at frequencies of every 5 and 10 d or were left undisturbed during each 30-d experimental period. At the end of each experiment, individual bricks were collected, periphyton biomass was estimated, and macroinvertebrates were identified and counted. Natural densities, taxon richness, and assemblage composition of macroinvertebrates differed significantly between sites and seasons. Periphyton biomass was higher in the open-canopy than in the closed-canopy site in both seasons, especially summer. Periphyton biomass differed among brick types at each site and season, but disturbance had no effect on periphyton biomass within a brick type. At the closed-canopy site, undisturbed hetero bricks had higher macroinvertebrate density, richness, and biomass than the other brick types and disturbance treatments in both seasons. At the open-canopy site, no effect of disturbance was found for any brick type in summer, whereas undisturbed and 10-d hetero bricks had higher macroinvertebrate density, richness, and biomass than the other brick types and disturbance treatments in winter. Besides the dominant role of site and season in this study, our results also suggest that substrate patch complexity can be significant in the response of macroinvertebrates to physical disturbance in regulated streams. As in natural systems, coarse-scale attributes of stream reaches, e.g., degree of canopy cover and season, also provide the spatiotemporal hierarchical context in which disturbance effects are realized in regulated streams, thus having major implications for resource managers.","PeriodicalId":49987,"journal":{"name":"Journal of the North American Benthological Society","volume":"89 1","pages":"374 - 385"},"PeriodicalIF":0.0,"publicationDate":"2011-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90420101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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