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Elisabeth K V Kalko - One of the best experts on this subject based on the ideXlab platform.
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Keystone Species in seed dispersal networks are mainly determined by dietary specialization
Oikos, 2015Co-Authors: Marco A. R. Mello, Francisco Aparecido Rodrigues, Luciano Da Fontoura Costa, Daniel W Kissling, Cagan H Sekercioglu, Flavia Maria Darcie Marquitti, Elisabeth K V KalkoAbstract:A central issue in ecology is the definition and identification of Keystone Species, i.e. Species that are relatively more important than others for maintaining community structure and ecosystem functioning. Network theory has been pointed out as a robust theoretical framework to enhance the operationality of the Keystone Species concept. We used the concept of centrality as a proxy for a Species’ relative importance for the structure of seed dispersal networks composed of either frugivorous bats or birds and their food-plants. Centrality was expected to be determined mainly by dietary specialization, but also by body mass and geographic range size. Across 15 Neotropical datasets, only specialized frugivore Species reached the highest values of centrality. Furthermore, the centrality of specialized frugivores varied widely within and among networks, whereas that of secondary and opportunistic frugivores was consistently low. A mixed-effects model showed that centrality was best explained by dietary specialization, but not by body mass or range size. Furthermore, the relationship between centrality and those three ecological correlates differed between bat- and bird-fruit networks. Our findings suggest that dietary specialization is key to understand what makes a frugivore Species a Keystone in seed dispersal networks, and that taxonomic identity also plays a significant role. Specialized frugivores may play a central role in network structuring and ecosystem functioning, which has important implications for conservation and restoration.
Miguel Delibesmateos - One of the best experts on this subject based on the ideXlab platform.
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the paradox of Keystone Species persecuted as pests a call for the conservation of abundant small mammals in their native range
Biological Conservation, 2011Co-Authors: Miguel Delibesmateos, Andrew T Smith, C N Slobodchikoff, Jon E SwensonAbstract:Small mammals, such as European rabbits (Oryctolagus cuniculus), plateau pikas (Ochotona curzoniae) and prairie dogs (Cynomys spp.), traditionally have been perceived as pests and targeted for control within their native ranges, where they perform essential ecosystem roles and are considered Keystone Species. These Species can reach high densities, and have been subjected to eradication campaigns because of their putative negative impact on natural habitats and agriculture and their competition with livestock for forage. Eradication programmes have been a main factor causing sharp declines of these Species in their natural ranges. Paradoxically, they are Keystone Species where they are abundant enough to be perceived as pests. The term “pest” is usually a social perception that is rarely supported by scientific data, whereas there is considerable scientific evidence of the key ecological roles played by these Species. We call for the conservation of these Species and present a conceptual model regarding the management of their populations. Where they occur at high numbers, and hence their effects on biodiversity are still of crucial importance, the persecution of these Species should be avoided and their natural habitats preserved. In areas with high conservation value, but where these Species occur at low densities, management efforts should aim to increase their density. In areas of high commercial value, managers ideally should consider changing prioritization of the area to high conservation value by purchasing the land or obtaining conservation easements. In situations with high commercial value and demonstrable low conservation concern, small mammals could be reduced humanely.
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rabbits as a Keystone Species in southern europe
Biological Conservation, 2007Co-Authors: Miguel Delibesmateos, Steve Redpath, Elena Angulo, Pablo Ferreras, Rafael VillafuerteAbstract:A Keystone Species is one that is crucial in maintaining the organization and diversity of their ecological communities. We tested the idea that rabbits act as a Keystone Species in southern Europe by exploring relationships between rabbit abundance and the abundance and diversity of raptor Species. At 20 sites in southern Spain we assessed rabbit abundance through counts of animals along transects and assessed the number of raptor individuals and Species through watches from vantage points. In a further 120 locations we also derived an index of rabbit abundance, from pellets and compared this to the presence or absence of the critically endangered Spanish imperial eagle. Rabbit abundance was positively associated with the number of observations of raptors, the number of raptor Species and the number of Species of conservation concern. Sites with the most rabbits had higher conservation value. Moreover, the presence of Spanish imperial eagle was strongly associated with sites where rabbits were at high density. We conclude that rabbits do act as a Keystone Species and we suggest that conservation efforts should focus on improving the status of this small-game Species in southern Europe.
Natasha B Kotliar - One of the best experts on this subject based on the ideXlab platform.
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application of the new Keystone Species concept to prairie dogs how well does it work
Conservation Biology, 2000Co-Authors: Natasha B KotliarAbstract:Abstract: It has been suggested that the Keystone-Species concept should be dropped from ecology and conservation, primarily because the concept is poorly defined. This prompted Power et al. (1996) to refine the definition: Keystone Species have large effects on community structure or ecosystem function (i.e., high overall importance), and this effect should be large relative to abundance (i.e., high community importance). Using prairie dogs (Cynomys spp.) as an example, I review operational and conceptual difficulties encountered in applying this definition. As applied to prairie dogs, the implicit assumption that overall importance is a linear function of abundance is invalid. In addition, community importance is sensitive to abundance levels, the definition of community, and sampling scale. These problems arise largely from the equation for community importance, as used in conjunction with removal experiments at single abundance levels. I suggest that we shift from the current emphasis on the dualism between Keystone and nonKeystone Species and instead examine how overall and community importance vary (1) with abundance, (2) across spatial and temporal scales, and (3) under diverse ecological conditions. In addition, I propose that a third criterion be incorporated into the definition: Keystone Species perform roles not performed by other Species or processes. Examination of how these factors vary among populations of Keystone Species should help identify the factors contributing to, or limiting, Keystone-level functions, thereby increasing the usefulness of the Keystone-Species concept in ecology and conservation. Although the quantitative framework of Power et al. falls short of being fully operational, my conceptual guidelines may improve the usefulness of the Keystone-Species concept. Careful attention to the factors that limit Keystone function will help avoid misplaced emphasis on Keystone Species at the expense of other Species.
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Application of the New Keystone‐Species Concept to Prairie Dogs: How Well Does It Work?
Conservation Biology, 2000Co-Authors: Natasha B KotliarAbstract:Abstract: It has been suggested that the Keystone-Species concept should be dropped from ecology and conservation, primarily because the concept is poorly defined. This prompted Power et al. (1996) to refine the definition: Keystone Species have large effects on community structure or ecosystem function (i.e., high overall importance), and this effect should be large relative to abundance (i.e., high community importance). Using prairie dogs (Cynomys spp.) as an example, I review operational and conceptual difficulties encountered in applying this definition. As applied to prairie dogs, the implicit assumption that overall importance is a linear function of abundance is invalid. In addition, community importance is sensitive to abundance levels, the definition of community, and sampling scale. These problems arise largely from the equation for community importance, as used in conjunction with removal experiments at single abundance levels. I suggest that we shift from the current emphasis on the dualism between Keystone and nonKeystone Species and instead examine how overall and community importance vary (1) with abundance, (2) across spatial and temporal scales, and (3) under diverse ecological conditions. In addition, I propose that a third criterion be incorporated into the definition: Keystone Species perform roles not performed by other Species or processes. Examination of how these factors vary among populations of Keystone Species should help identify the factors contributing to, or limiting, Keystone-level functions, thereby increasing the usefulness of the Keystone-Species concept in ecology and conservation. Although the quantitative framework of Power et al. falls short of being fully operational, my conceptual guidelines may improve the usefulness of the Keystone-Species concept. Careful attention to the factors that limit Keystone function will help avoid misplaced emphasis on Keystone Species at the expense of other Species.
Ferenc Jordan - One of the best experts on this subject based on the ideXlab platform.
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food web topology and nested Keystone Species complexes
Complexity, 2018Co-Authors: Daniele Capocefalo, Juliana Pereira, Tommaso Mazza, Ferenc JordanAbstract:Important Species may be in critically central network positions in ecological interaction networks. Beyond quantifying which one is the most central Species in a food web, a multinode approach can identify the key sets of the most central Species as well. However, for sets of different size , these structural Keystone Species complexes may differ in their composition. If larger sets contain smaller sets, higher nestedness may be a proxy for predictive ecology and efficient management of ecosystems. On the contrary, lower nestedness makes the identification of Keystones more complicated. Our question here is how the topology of a network can influence nestedness as an architectural constraint. Here, we study the role of Keystone Species complexes in 27 real food webs and quantify their nestedness. After quantifying their topology properties, we determine their Keystone Species complexes, calculate their nestedness, and statistically analyze the relationship between topological indices and nestedness. A better understanding of the cores of ecosystems is crucial for efficient conservation efforts, and to know which networks will have more nested Keystone Species complexes would be a great help for prioritizing Species that could preserve the ecosystem’s structural integrity.
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Keystone Species and food webs
Philosophical Transactions of the Royal Society B, 2009Co-Authors: Ferenc JordanAbstract:Different Species are of different importance in maintaining ecosystem functions in natural communities. Quantitative approaches are needed to identify unusually important or influential, ‘Keystone’ Species particularly for conservation purposes. Since the importance of some Species may largely be the consequence of their rich interaction structure, one possible quantitative approach to identify the most influential Species is to study their position in the network of interspecific interactions. In this paper, I discuss the role of network analysis (and centrality indices in particular) in this process and present a new and simple approach to characterizing the interaction structures of each Species in a complex network. Understanding the linkage between structure and dynamics is a condition to test the results of topological studies, I briefly overview our current knowledge on this issue. The study of key nodes in networks has become an increasingly general interest in several disciplines: I will discuss some parallels. Finally, I will argue that conservation biology needs to devote more attention to identify and conserve Keystone Species and relatively less attention to rarity.
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topological Keystone Species measures of positional importance in food webs
Oikos, 2006Co-Authors: Ferenc Jordan, Andrew J DavisAbstract:The local extinction or large fluctuation in abundance of a Species may seriously affect other Species in the community. The effects spread through the community by direct and indirect interactions. The network perspective on ecology can help map the pathways of these effects, for food webs, the pathways of indirect trophic interactions. Indirect interactions typically decay in intensity as they spread. Therefore, there is a conceptual maximum range in topological space beyond which interactions have no effects, even though all Species remain connected. Neither the local characteristics of Species, nor the global characteristics of entire webs, suitably quantify this range. We therefore apply intermediate scale indices that reflect the limitations imposed by effect damping in networks. We present a complex analysis of the topological positional importance of Species in the Chesapeake Bay web. This web is a carbon-flow network that represents trophic interactions. We present several different indices reflecting different properties and discuss which questions the different indices best answer. We look for the best indices for identifying the key players in ecosystem functioning. Our study contributes to the quantification of relative Species importance and provides an exact and a priori determination of a class of candidate Keystone Species that can inform applied and conservation ecology as well as theoretical concerns.
Marco A. R. Mello - One of the best experts on this subject based on the ideXlab platform.
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Keystone Species
Ecology, 2019Co-Authors: Marco A. R. MelloAbstract:If you take the Keystone from an arch, it falls apart. However, does the same happen when you remove a Species from its ecological community? This question has intrigued scientists for centuries, and examples of “very important Species” in natural, urban, and agricultural systems abound. Looking at this problem from another perspective, one might say that ecology would not be the same if one central concept were removed from its literature: Keystone Species. In two seminal papers published in 1966 and 1969, the American ecologist Robert T. Paine (b. 1933–d. 2016) defined a Keystone as a Species whose activities greatly modify “the composition and physical appearance” of its community. He proposed an experimental approach to the problem and transformed the quest for Keystones into one of the most prolific ecological research programs. Since then, at least 1,658 papers recorded on Web of Science (consulted on 4 September 2018, using the expression “Keystone Species”) focused on testing, refining, or expanding the Keystone Species concept. Those papers were cited 60,754 times by 48,309 other papers published in 845 journals, and the number of citations keeps growing. It is hard to think of any other topic in ecology, a field marked by constant changes in focus, which drew so much attention for such a long time. In Paine’s original experiments, the Keystones were starfish and gastropods that preyed on other marine invertebrates, weaving complex webs of direct and indirect effects that regulate the abundances of all other Species in the community. This metaphor was expanded in the next decades to several other Species from a myriad of taxa in a multitude of contexts, from prairie dogs to fruiting trees and even humans. This boom raised much controversy related to which criteria should be used to label a Species a Keystone. Even the original interpretation of Paine’s experiments has been cast in doubt due to issues of replicability. Nevertheless, there is a consensus that the Keystone Species concept has at least high heuristic value. Moreover, it is supported by empirical evidence accumulated over the decades. Now studied under different theoretical frameworks, such as community ecology, ecosystem engineers, and ecological networks, it remains a hot topic. The Keystone Species concept led to significant developments in many different fields and may be considered a theoretical framework on its own. In this bibliography, the origins of the concept are retraced, as well as its development and current usage.
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Keystone Species in seed dispersal networks are mainly determined by dietary specialization
Oikos, 2015Co-Authors: Marco A. R. Mello, Francisco Aparecido Rodrigues, Luciano Da Fontoura Costa, Daniel W Kissling, Cagan H Sekercioglu, Flavia Maria Darcie Marquitti, Elisabeth K V KalkoAbstract:A central issue in ecology is the definition and identification of Keystone Species, i.e. Species that are relatively more important than others for maintaining community structure and ecosystem functioning. Network theory has been pointed out as a robust theoretical framework to enhance the operationality of the Keystone Species concept. We used the concept of centrality as a proxy for a Species’ relative importance for the structure of seed dispersal networks composed of either frugivorous bats or birds and their food-plants. Centrality was expected to be determined mainly by dietary specialization, but also by body mass and geographic range size. Across 15 Neotropical datasets, only specialized frugivore Species reached the highest values of centrality. Furthermore, the centrality of specialized frugivores varied widely within and among networks, whereas that of secondary and opportunistic frugivores was consistently low. A mixed-effects model showed that centrality was best explained by dietary specialization, but not by body mass or range size. Furthermore, the relationship between centrality and those three ecological correlates differed between bat- and bird-fruit networks. Our findings suggest that dietary specialization is key to understand what makes a frugivore Species a Keystone in seed dispersal networks, and that taxonomic identity also plays a significant role. Specialized frugivores may play a central role in network structuring and ecosystem functioning, which has important implications for conservation and restoration.
