Kevin Mccann - Academia.edu (original) (raw)
Papers by Kevin Mccann
Global change is fundamentally altering flows of natural and anthropogenic subsidies across space... more Global change is fundamentally altering flows of natural and anthropogenic subsidies across space and time. After a pointed call for research on subsidies in the 1990s, an industry of empirical work has documented the ubiquitous role subsidies play in ecosystem structure, stability and function. Here, we argue that physical constraints (e.g., water temperature) and species traits can govern a species’ accessibility to resource subsidies, and that these physical constraints have been largely overlooked in the subsidy literature. We examined the input of a high quality, point-source anthropogenic subsidy into a recipient freshwater lake food web (i.e., released net-pen aquaculture feed in Parry Sound, Lake Huron), to demonstrate the importance of subsidy accessibility in governing recipient whole food web responses. By using a combined bio-tracer approach, we detect a gradient in accessibility of the anthropogenic subsidy within the surrounding food web driven by the thermal tolerance...
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bioRxiv (Cold Spring Harbor Laboratory), Apr 15, 2020
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The ecological consequences of winter in freshwater systems are an understudied but rapidly emerg... more The ecological consequences of winter in freshwater systems are an understudied but rapidly emerging research area. Here, we argue that winter periods of reduced temperature and light (and potentially oxygen and resources) could play an underappreciated role in mediating the coexistence of species. This may be especially true for temperate and subarctic lakes, where seasonal changes in the thermal environment might fundamentally structure species interactions. With climate change already shortening ice-covered periods on temperate and polar lakes, consideration of how winter conditions shape biotic interactions is urgently needed. Using freshwater fishes in northern temperate lakes as a case study, we demonstrate how physiological trait differences (e.g., thermal preference, light sensitivity) drive differential behavioral responses to winter among competing species. Specifically, some species have a higher capacity for winter activity than others. Existing and new theory is present...
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Transactions of the American Fisheries Society, 2018
Northern Pike Esox lucius are important aquatic apex predators in freshwater ecosystems across th... more Northern Pike Esox lucius are important aquatic apex predators in freshwater ecosystems across the Canadian Boreal Shield. Although Northern Pike have historically been described as nearshore ambush predators, larger individuals have been anecdotally observed foraging in offshore habitats. We used two province‐wide data sets from Ontario, Canada, to investigate the degree to which Northern Pike are generalist predators by examining the influence of offshore prey fish densities on their life histories. To better understand whether the life history patterns observed were unique to Northern Pike or representative of aquatic apex predators generally, we compared Northern Pike life history and catch results to those of the Lake Trout Salvelinus namaycush, a well‐known pelagic apex predator. We found that the asymptotic lengths of both Northern Pike and Lake Trout were positively related to Cisco Coregonus artedi CPUE. Furthermore, both Northern Pike and Lake Trout occupied offshore habit...
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Food Webs, 2018
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Ecology, 2019
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Ecology letters, 2018
Classically, biomass partitioning across trophic levels was thought to add up to a pyramidal dist... more Classically, biomass partitioning across trophic levels was thought to add up to a pyramidal distribution. Numerous exceptions have, however, been noted including complete pyramidal inversions. Elevated levels of biomass top-heaviness (i.e. high consumer/resource biomass ratios) have been reported from Arctic tundra communities to Brazilian phytotelmata, and in species assemblages as diverse as those dominated by sharks and ants. We highlight two major pathways for creating top-heaviness, via: (1) endogenous channels that enhance energy transfer across trophic boundaries within a community and (2) exogenous pathways that transfer energy into communities from across spatial and temporal boundaries. Consumer-resource models and allometric trophic network models combined with niche models reveal the nature of core mechanisms for promoting top-heaviness. Outputs from these models suggest that top-heavy communities can be stable, but they also reveal sources of instability. Humans are bo...
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Nature, 1998
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Trends in Ecology & Evolution, 2015
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Canadian Journal of Fisheries and Aquatic Sciences, 2016
Here, we introduce a novel theory for multispecies fisheries that exploit fish stocks evenly with... more Here, we introduce a novel theory for multispecies fisheries that exploit fish stocks evenly within and across trophic levels in an entire ecosystem (i.e., fishery comprises all fleets). These “indiscriminate” fisheries may be common in developing countries where fish provide the main source of dietary protein. We show that simple food web modules, motivated by empirical patterns in body size and energy flow, yield general and robust predictions about the fate of such a fishery. Specifically, high and uniform fishing mortality modifies the fish community in a manner that leads to increased productive capacity from a low-diversity assemblage of small-bodied fish with rapid population growth and turnover (the productive monoculture effect). We then argue that catches are relatively indiscriminate in the Tonlé Sap, a highly productive inland fishery in Cambodia that feeds millions, and show consistent qualitative agreement between the theory of indiscriminate fishing and this existing ...
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F1000 - Post-publication peer review of the biomedical literature, 2005
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The American naturalist, 2015
Trophic cascades are indirect positive effects of predators on resources via control of intermedi... more Trophic cascades are indirect positive effects of predators on resources via control of intermediate consumers. Larger-bodied predators appear to induce stronger trophic cascades (a greater rebound of resource density toward carrying capacity), but how this happens is unknown because we lack a clear depiction of how the strength of trophic cascades is determined. Using consumer resource models, we first show that the strength of a trophic cascade has an upper limit set by the interaction strength between the basal trophic group and its consumer and that this limit is approached as the interaction strength between the consumer and its predator increases. We then express the strength of a trophic cascade explicitly in terms of predator body size and use two independent parameter sets to calculate how the strength of a trophic cascade depends on predator size. Both parameter sets predict a positive effect of predator size on the strength of a trophic cascade, driven mostly by the body ...
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Trends in Ecology & Evolution, 2012
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The American Naturalist, 1998
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Proceedings of the Royal Society of London. Series B: Biological Sciences, 1997
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Proceedings of the National Academy of Sciences, 2014
Significance Organisms may adjust their behavior to stay cool as natural habitats differentially ... more Significance Organisms may adjust their behavior to stay cool as natural habitats differentially warm with rising air temperature. Undoubtedly, fundamental ecosystem properties will change in turn, but the impact of the dynamic thermal mosaic on food web interactions is not considered in traditional climate change research. To demonstrate differential warming effects on food webs, we use boreal lakes to show that the energy pathways leading to an apex predator shift, according to thermal preference, and the vertical pathway lengthened in warmer climate. Such a fundamental food web restructuring is expected to increase predator contaminant levels and alter community dynamics in ecosystems—a particular concern for conservation of boreal lakes, which house a significant portion of Earth’s freshwater life.
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Proceedings of the National Academy of Sciences, 2007
Patterns in food-web structure have frequently been examined in static food webs, but few studies... more Patterns in food-web structure have frequently been examined in static food webs, but few studies have attempted to delineate patterns that materialize in food webs under nonequilibrium conditions. Here, using one of nature's classical nonequilibrium systems as the food-web database, we test the major assumptions of recent advances in food-web theory. We show that a complex web of interactions between insect herbivores and their natural enemies displays significant architectural flexibility over a large fluctuation in the natural abundance of the major herbivore, the spruce budworm ( Choristoneura fumiferana ). Importantly, this flexibility operates precisely in the manner predicted by recent foraging-based food-web theories: higher-order mobile generalists respond rapidly in time and space by converging on areas of increasing prey abundance. This “birdfeeder effect” operates such that increasing budworm densities correspond to a cascade of increasing diversity and food-web comp...
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Philosophical Transactions of the Royal Society B: Biological Sciences, 2009
Here, we synthesize a number of recent empirical and theoretical papers to argue that food-web dy... more Here, we synthesize a number of recent empirical and theoretical papers to argue that food-web dynamics are characterized by high amounts of spatial and temporal variability and that organisms respond predictably, via behaviour, to these changing conditions. Such behavioural responses on the landscape drive a highly adaptive food-web structure in space and time. Empirical evidence suggests that underlying attributes of food webs are potentially scale-invariant such that food webs are characterized by hump-shaped trophic structures with fast and slow pathways that repeat at different resolutions within the food web. We place these empirical patterns within the context of recent food-web theory to show that adaptable food-web structure confers stability to an assemblage of interacting organisms in a variable world. Finally, we show that recent food-web analyses agree with two of the major predictions of this theory. We argue that the next major frontier in food-web theory and applied ...
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Oikos, 2009
Habitat coupling is an ecosystem process whereby semi‐discontinuous habitats are connected throug... more Habitat coupling is an ecosystem process whereby semi‐discontinuous habitats are connected through the movement of energy and nutrients by chemical, physical or biological processes. One oft‐cited example is that of littoral–pelagic coupling in lakes. Theory has argued that such habitat coupling may be critical to food web dynamics, yet there have been few empirical studies that have quantified ecological factors that affect the degree of habitat coupling in ecosystems. Specifically, the degree to which habitat coupling occurs across important physical gradients has largely been ignored. To address this, we investigate the degree of littoral habitat coupling (i.e. the degree to which a top predator lake trout, Salvelinus namaycush, derives energy from the littoral zone) along a gradient of lake shape, where lake shape modifies the relative quantity of coupled epilimnetic benthic and pelagic habitats within each lake. Herein we demonstrate that littoral habitat coupling is intensifie...
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Nature Communications, 2012
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Global change is fundamentally altering flows of natural and anthropogenic subsidies across space... more Global change is fundamentally altering flows of natural and anthropogenic subsidies across space and time. After a pointed call for research on subsidies in the 1990s, an industry of empirical work has documented the ubiquitous role subsidies play in ecosystem structure, stability and function. Here, we argue that physical constraints (e.g., water temperature) and species traits can govern a species’ accessibility to resource subsidies, and that these physical constraints have been largely overlooked in the subsidy literature. We examined the input of a high quality, point-source anthropogenic subsidy into a recipient freshwater lake food web (i.e., released net-pen aquaculture feed in Parry Sound, Lake Huron), to demonstrate the importance of subsidy accessibility in governing recipient whole food web responses. By using a combined bio-tracer approach, we detect a gradient in accessibility of the anthropogenic subsidy within the surrounding food web driven by the thermal tolerance...
Bookmarks Related papers MentionsView impact
bioRxiv (Cold Spring Harbor Laboratory), Apr 15, 2020
Bookmarks Related papers MentionsView impact
The ecological consequences of winter in freshwater systems are an understudied but rapidly emerg... more The ecological consequences of winter in freshwater systems are an understudied but rapidly emerging research area. Here, we argue that winter periods of reduced temperature and light (and potentially oxygen and resources) could play an underappreciated role in mediating the coexistence of species. This may be especially true for temperate and subarctic lakes, where seasonal changes in the thermal environment might fundamentally structure species interactions. With climate change already shortening ice-covered periods on temperate and polar lakes, consideration of how winter conditions shape biotic interactions is urgently needed. Using freshwater fishes in northern temperate lakes as a case study, we demonstrate how physiological trait differences (e.g., thermal preference, light sensitivity) drive differential behavioral responses to winter among competing species. Specifically, some species have a higher capacity for winter activity than others. Existing and new theory is present...
Bookmarks Related papers MentionsView impact
Transactions of the American Fisheries Society, 2018
Northern Pike Esox lucius are important aquatic apex predators in freshwater ecosystems across th... more Northern Pike Esox lucius are important aquatic apex predators in freshwater ecosystems across the Canadian Boreal Shield. Although Northern Pike have historically been described as nearshore ambush predators, larger individuals have been anecdotally observed foraging in offshore habitats. We used two province‐wide data sets from Ontario, Canada, to investigate the degree to which Northern Pike are generalist predators by examining the influence of offshore prey fish densities on their life histories. To better understand whether the life history patterns observed were unique to Northern Pike or representative of aquatic apex predators generally, we compared Northern Pike life history and catch results to those of the Lake Trout Salvelinus namaycush, a well‐known pelagic apex predator. We found that the asymptotic lengths of both Northern Pike and Lake Trout were positively related to Cisco Coregonus artedi CPUE. Furthermore, both Northern Pike and Lake Trout occupied offshore habit...
Bookmarks Related papers MentionsView impact
Food Webs, 2018
Bookmarks Related papers MentionsView impact
Ecology, 2019
Bookmarks Related papers MentionsView impact
Ecology letters, 2018
Classically, biomass partitioning across trophic levels was thought to add up to a pyramidal dist... more Classically, biomass partitioning across trophic levels was thought to add up to a pyramidal distribution. Numerous exceptions have, however, been noted including complete pyramidal inversions. Elevated levels of biomass top-heaviness (i.e. high consumer/resource biomass ratios) have been reported from Arctic tundra communities to Brazilian phytotelmata, and in species assemblages as diverse as those dominated by sharks and ants. We highlight two major pathways for creating top-heaviness, via: (1) endogenous channels that enhance energy transfer across trophic boundaries within a community and (2) exogenous pathways that transfer energy into communities from across spatial and temporal boundaries. Consumer-resource models and allometric trophic network models combined with niche models reveal the nature of core mechanisms for promoting top-heaviness. Outputs from these models suggest that top-heavy communities can be stable, but they also reveal sources of instability. Humans are bo...
Bookmarks Related papers MentionsView impact
Nature, 1998
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Trends in Ecology & Evolution, 2015
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Canadian Journal of Fisheries and Aquatic Sciences, 2016
Here, we introduce a novel theory for multispecies fisheries that exploit fish stocks evenly with... more Here, we introduce a novel theory for multispecies fisheries that exploit fish stocks evenly within and across trophic levels in an entire ecosystem (i.e., fishery comprises all fleets). These “indiscriminate” fisheries may be common in developing countries where fish provide the main source of dietary protein. We show that simple food web modules, motivated by empirical patterns in body size and energy flow, yield general and robust predictions about the fate of such a fishery. Specifically, high and uniform fishing mortality modifies the fish community in a manner that leads to increased productive capacity from a low-diversity assemblage of small-bodied fish with rapid population growth and turnover (the productive monoculture effect). We then argue that catches are relatively indiscriminate in the Tonlé Sap, a highly productive inland fishery in Cambodia that feeds millions, and show consistent qualitative agreement between the theory of indiscriminate fishing and this existing ...
Bookmarks Related papers MentionsView impact
F1000 - Post-publication peer review of the biomedical literature, 2005
Bookmarks Related papers MentionsView impact
The American naturalist, 2015
Trophic cascades are indirect positive effects of predators on resources via control of intermedi... more Trophic cascades are indirect positive effects of predators on resources via control of intermediate consumers. Larger-bodied predators appear to induce stronger trophic cascades (a greater rebound of resource density toward carrying capacity), but how this happens is unknown because we lack a clear depiction of how the strength of trophic cascades is determined. Using consumer resource models, we first show that the strength of a trophic cascade has an upper limit set by the interaction strength between the basal trophic group and its consumer and that this limit is approached as the interaction strength between the consumer and its predator increases. We then express the strength of a trophic cascade explicitly in terms of predator body size and use two independent parameter sets to calculate how the strength of a trophic cascade depends on predator size. Both parameter sets predict a positive effect of predator size on the strength of a trophic cascade, driven mostly by the body ...
Bookmarks Related papers MentionsView impact
Trends in Ecology & Evolution, 2012
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The American Naturalist, 1998
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Proceedings of the Royal Society of London. Series B: Biological Sciences, 1997
Bookmarks Related papers MentionsView impact
Proceedings of the National Academy of Sciences, 2014
Significance Organisms may adjust their behavior to stay cool as natural habitats differentially ... more Significance Organisms may adjust their behavior to stay cool as natural habitats differentially warm with rising air temperature. Undoubtedly, fundamental ecosystem properties will change in turn, but the impact of the dynamic thermal mosaic on food web interactions is not considered in traditional climate change research. To demonstrate differential warming effects on food webs, we use boreal lakes to show that the energy pathways leading to an apex predator shift, according to thermal preference, and the vertical pathway lengthened in warmer climate. Such a fundamental food web restructuring is expected to increase predator contaminant levels and alter community dynamics in ecosystems—a particular concern for conservation of boreal lakes, which house a significant portion of Earth’s freshwater life.
Bookmarks Related papers MentionsView impact
Proceedings of the National Academy of Sciences, 2007
Patterns in food-web structure have frequently been examined in static food webs, but few studies... more Patterns in food-web structure have frequently been examined in static food webs, but few studies have attempted to delineate patterns that materialize in food webs under nonequilibrium conditions. Here, using one of nature's classical nonequilibrium systems as the food-web database, we test the major assumptions of recent advances in food-web theory. We show that a complex web of interactions between insect herbivores and their natural enemies displays significant architectural flexibility over a large fluctuation in the natural abundance of the major herbivore, the spruce budworm ( Choristoneura fumiferana ). Importantly, this flexibility operates precisely in the manner predicted by recent foraging-based food-web theories: higher-order mobile generalists respond rapidly in time and space by converging on areas of increasing prey abundance. This “birdfeeder effect” operates such that increasing budworm densities correspond to a cascade of increasing diversity and food-web comp...
Bookmarks Related papers MentionsView impact
Philosophical Transactions of the Royal Society B: Biological Sciences, 2009
Here, we synthesize a number of recent empirical and theoretical papers to argue that food-web dy... more Here, we synthesize a number of recent empirical and theoretical papers to argue that food-web dynamics are characterized by high amounts of spatial and temporal variability and that organisms respond predictably, via behaviour, to these changing conditions. Such behavioural responses on the landscape drive a highly adaptive food-web structure in space and time. Empirical evidence suggests that underlying attributes of food webs are potentially scale-invariant such that food webs are characterized by hump-shaped trophic structures with fast and slow pathways that repeat at different resolutions within the food web. We place these empirical patterns within the context of recent food-web theory to show that adaptable food-web structure confers stability to an assemblage of interacting organisms in a variable world. Finally, we show that recent food-web analyses agree with two of the major predictions of this theory. We argue that the next major frontier in food-web theory and applied ...
Bookmarks Related papers MentionsView impact
Oikos, 2009
Habitat coupling is an ecosystem process whereby semi‐discontinuous habitats are connected throug... more Habitat coupling is an ecosystem process whereby semi‐discontinuous habitats are connected through the movement of energy and nutrients by chemical, physical or biological processes. One oft‐cited example is that of littoral–pelagic coupling in lakes. Theory has argued that such habitat coupling may be critical to food web dynamics, yet there have been few empirical studies that have quantified ecological factors that affect the degree of habitat coupling in ecosystems. Specifically, the degree to which habitat coupling occurs across important physical gradients has largely been ignored. To address this, we investigate the degree of littoral habitat coupling (i.e. the degree to which a top predator lake trout, Salvelinus namaycush, derives energy from the littoral zone) along a gradient of lake shape, where lake shape modifies the relative quantity of coupled epilimnetic benthic and pelagic habitats within each lake. Herein we demonstrate that littoral habitat coupling is intensifie...
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Nature Communications, 2012
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