2021
Power, Mary E.
Synthetic threads through the web of life Journal Article
In: PNAS, 2021.
Abstract | Links | BibTeX | Tags: CRISPR, ecological impacts, gene drives, interaction strength, scale linkages
@article{Power2021,
title = {Synthetic threads through the web of life},
author = {Mary E. Power},
doi = {10.1073/pnas.2004833118},
year = {2021},
date = {2021-04-30},
journal = {PNAS},
abstract = {CRISPR-Cas gene editing tools have brought us to an era of synthetic biology that will change the world. Excitement over the breakthroughs these tools have enabled in biology and medicine is balanced, justifiably, by concern over how their applications might go wrong in open environments. We do not know how genomic processes (including regulatory and epigenetic processes), evolutionary change, ecosystem interactions, and other higher order processes will affect traits, fitness, and impacts of edited organisms in nature. However, anticipating the spread, change, and impacts of edited traits or organisms in heterogeneous, changing environments is particularly important with “gene drives on the horizon.” To anticipate how “synthetic threads” will affect the web of life on Earth, scientists must confront complex system interactions across many levels of biological organization. Currently, we lack plans, infrastructure, and funding for field science and scientists to track new synthetic organisms, with or without gene drives, as they move through open environments.},
keywords = {CRISPR, ecological impacts, gene drives, interaction strength, scale linkages},
pubstate = {published},
tppubtype = {article}
}
CRISPR-Cas gene editing tools have brought us to an era of synthetic biology that will change the world. Excitement over the breakthroughs these tools have enabled in biology and medicine is balanced, justifiably, by concern over how their applications might go wrong in open environments. We do not know how genomic processes (including regulatory and epigenetic processes), evolutionary change, ecosystem interactions, and other higher order processes will affect traits, fitness, and impacts of edited organisms in nature. However, anticipating the spread, change, and impacts of edited traits or organisms in heterogeneous, changing environments is particularly important with “gene drives on the horizon.” To anticipate how “synthetic threads” will affect the web of life on Earth, scientists must confront complex system interactions across many levels of biological organization. Currently, we lack plans, infrastructure, and funding for field science and scientists to track new synthetic organisms, with or without gene drives, as they move through open environments.
2013
Power, Mary E.; Holomuzki, Joseph R.; Lowe, Rex L.
Food webs in Mediterranean rivers Journal Article
In: Hydrobiologia, vol. 719, no. 1, pp. 119-136, 2013.
Abstract | Links | BibTeX | Tags: Algal production, Cross-ecosystem fluxes, Detritus Disturbance, Drought, fate Carbon sources, Floods, Food quality, food webs, hydrology, Insect emergence, interaction strength, Mediterranean rivers, River-to-ocean fluxes, seasonality
@article{Power2013,
title = {Food webs in Mediterranean rivers},
author = {Mary E. Power and Joseph R. Holomuzki and Rex L. Lowe},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_2013_Hydrobio.pdf},
doi = {10.1007/s10750-013-1510-0},
year = {2013},
date = {2013-05-28},
journal = {Hydrobiologia},
volume = {719},
number = {1},
pages = {119-136},
abstract = {River food webs are subject to two regimes of longitudinally varying ecological control: productivity and disturbance. Light-limited productivity increases as channels widen downstream. Time windows for growth, however, shrink as discharge increases, substrate particle size decreases, and the frequency of flood-driven bed mobilization increases downstream. Mediterranean rivers are periodically reset by hydrologic events with somewhat predictable timing. Typically, a rainy winter with high river discharge is followed by summer drought with little or no rainfall and slowly declining river flow. The magnitude and timing of winter floods and severity of subsequent summer drought can vary considerably from year to year, however. Episodic scouring floods or prolonged periods of drought are experienced as disturbances, stressors, or opportunities by river biota. The timing, duration, and intensity of these hydrologic controls affect performances of individuals, distribution and abundances of populations, and outcomes and consequences of species interactions. These interactions in turn determine how river food webs will assemble, develop, and reconfigure after disturbance. We discuss how spatial variation in solar radiation and spatial and temporal variations in disturbance affects river food webs under Mediterranean climate seasonality, focusing primarily on long-term observations in the Eel River of northwestern California, USA},
keywords = {Algal production, Cross-ecosystem fluxes, Detritus Disturbance, Drought, fate Carbon sources, Floods, Food quality, food webs, hydrology, Insect emergence, interaction strength, Mediterranean rivers, River-to-ocean fluxes, seasonality},
pubstate = {published},
tppubtype = {article}
}
River food webs are subject to two regimes of longitudinally varying ecological control: productivity and disturbance. Light-limited productivity increases as channels widen downstream. Time windows for growth, however, shrink as discharge increases, substrate particle size decreases, and the frequency of flood-driven bed mobilization increases downstream. Mediterranean rivers are periodically reset by hydrologic events with somewhat predictable timing. Typically, a rainy winter with high river discharge is followed by summer drought with little or no rainfall and slowly declining river flow. The magnitude and timing of winter floods and severity of subsequent summer drought can vary considerably from year to year, however. Episodic scouring floods or prolonged periods of drought are experienced as disturbances, stressors, or opportunities by river biota. The timing, duration, and intensity of these hydrologic controls affect performances of individuals, distribution and abundances of populations, and outcomes and consequences of species interactions. These interactions in turn determine how river food webs will assemble, develop, and reconfigure after disturbance. We discuss how spatial variation in solar radiation and spatial and temporal variations in disturbance affects river food webs under Mediterranean climate seasonality, focusing primarily on long-term observations in the Eel River of northwestern California, USA
2008
Power, Mary E.; Parker, Michael S.; Dietrich, William E.
Seasonal Reassembly of a River Food Web: Floods, Droughts, and Impacts of Fish Journal Article
In: Ecological Monographs, vol. 78, no. 2, pp. 263–282, 2008, ISSN: 0012-9615.
Abstract | Links | BibTeX | Tags: Cladophora glomerata, context dependency, effect sizes, flood scour, food chain length, interaction strength, Lavinia (Hesperoleucas) symmetricus, long-term studies, Mediterranean hydrologic regimes, Oncorhynchus mykiss, population, predator impacts
@article{Power2008,
title = {Seasonal Reassembly of a River Food Web: Floods, Droughts, and Impacts of Fish},
author = {Mary E. Power and Michael S. Parker and William E. Dietrich},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_2008_EcoMono.pdf
https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_FoodWebDrouFloodFish_EcoMono2008.pdf
https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_AppA_EcoMono2008.pdf
https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_AppB_EcoMono2008.pdf},
doi = {10.1890/06-0902.1},
issn = {0012-9615},
year = {2008},
date = {2008-05-01},
journal = {Ecological Monographs},
volume = {78},
number = {2},
pages = {263–282},
abstract = {Eighteen years of field observations and five summer field experiments in a coastal California river suggest that hydrologic regimes influence algal blooms and the impacts of fish on algae, cyanobacteria, invertebrates, and small vertebrates. In this Mediterranean climate, rainy winters precede the biologically active summer low-flow season. Cladophora glomerata, the filamentous green alga that dominates primary producer biomass during summer, reaches peak biomass during late spring or early summer. Cladophora blooms are larger if floods during the preceding winter attained or exceeded ‘‘bankfull discharge’’ (sufficient to mobilize much of the river bed, estimated at 120 m3/s). In 9 out of 12 summers preceded by large bed-scouring floods, the average peak height of attached Cladophora turfs equaled or exceeded 50 cm. In five out of six years when flows remained below bankfull, Cladophora biomass peaked at lower levels. Flood effects on algae were partially mediated through impacts on consumers in food webs. In three experiments that followed scouring winter floods, juvenile steelhead (Oncorhynchus mykiss) and roach (Lavinia (Hesperoleucas) symmetricus) suppressed certain insects and young-of-the-year fish fry, affecting persistence or accrual of algae positively or negatively, depending on the predator-specific vulnerabilities of primary consumers capable of suppressing algae during a given year. During two post-flood years, these grazers were more vulnerable to small predators (odonates and fish fry, which stocked steelhead always suppressed) than to experimentally manipulated, larger fish, which had adverse effects on algae in those years. During one post-flood year, all enclosed grazers capable of suppressing algae were consumed by steelhead, which therefore had positive effects on algae. During drought years, when no bed-scouring winter flows occurred, large armored caddisflies (Dicosmoecus gilvipes) were more abundant during the subsequent summer. In drought-year experiments, stocked fish had little or no influence on algal standing crops, which increased only when Dicosmoecus were removed from enclosures. Flood scour, by suppressing invulnerable grazers, set the stage for fish mediated effects on algae in this river food web. Whether these effects were positive or negative depended on the predator-specific vulnerabilities of primary consumers that dominated during a given summer.},
keywords = {Cladophora glomerata, context dependency, effect sizes, flood scour, food chain length, interaction strength, Lavinia (Hesperoleucas) symmetricus, long-term studies, Mediterranean hydrologic regimes, Oncorhynchus mykiss, population, predator impacts},
pubstate = {published},
tppubtype = {article}
}
Eighteen years of field observations and five summer field experiments in a coastal California river suggest that hydrologic regimes influence algal blooms and the impacts of fish on algae, cyanobacteria, invertebrates, and small vertebrates. In this Mediterranean climate, rainy winters precede the biologically active summer low-flow season. Cladophora glomerata, the filamentous green alga that dominates primary producer biomass during summer, reaches peak biomass during late spring or early summer. Cladophora blooms are larger if floods during the preceding winter attained or exceeded ‘‘bankfull discharge’’ (sufficient to mobilize much of the river bed, estimated at 120 m3/s). In 9 out of 12 summers preceded by large bed-scouring floods, the average peak height of attached Cladophora turfs equaled or exceeded 50 cm. In five out of six years when flows remained below bankfull, Cladophora biomass peaked at lower levels. Flood effects on algae were partially mediated through impacts on consumers in food webs. In three experiments that followed scouring winter floods, juvenile steelhead (Oncorhynchus mykiss) and roach (Lavinia (Hesperoleucas) symmetricus) suppressed certain insects and young-of-the-year fish fry, affecting persistence or accrual of algae positively or negatively, depending on the predator-specific vulnerabilities of primary consumers capable of suppressing algae during a given year. During two post-flood years, these grazers were more vulnerable to small predators (odonates and fish fry, which stocked steelhead always suppressed) than to experimentally manipulated, larger fish, which had adverse effects on algae in those years. During one post-flood year, all enclosed grazers capable of suppressing algae were consumed by steelhead, which therefore had positive effects on algae. During drought years, when no bed-scouring winter flows occurred, large armored caddisflies (Dicosmoecus gilvipes) were more abundant during the subsequent summer. In drought-year experiments, stocked fish had little or no influence on algal standing crops, which increased only when Dicosmoecus were removed from enclosures. Flood scour, by suppressing invulnerable grazers, set the stage for fish mediated effects on algae in this river food web. Whether these effects were positive or negative depended on the predator-specific vulnerabilities of primary consumers that dominated during a given summer.
- https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_2008_EcoMono.pdf
- https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_FoodWebDrouFloodFi[…]
- https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_AppA_EcoMono2008.p[…]
- https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_AppB_EcoMono2008.p[…]
- doi:10.1890/06-0902.1
1999
Berlow, Eric L.; Navarrete, Sergio A.; Briggs, Cheryl J.; Power, Mary E.; Menge, Bruce A.
Quantifying variation in the strengths of species interactions Journal Article
In: Ecology, vol. 80, no. 7, pp. 2206-2224, 1999, ISSN: 0012-9658.
Abstract | Links | BibTeX | Tags: density dependence, food web, functional response, interaction strength, keystone species, per capita effects, predator–prey interaction, simulation, species impact, species interactions
@article{Berlow1999,
title = {Quantifying variation in the strengths of species interactions},
author = {Eric L. Berlow and Sergio A. Navarrete and Cheryl J. Briggs and Mary E. Power and Bruce A. Menge},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/QUANTIFYING-VARIATION-IN-THE-STRENGTHS-OF-SPECIES-INTERACTIONS_Berlow_1999.pdf},
doi = {10.1890/0012-9658(1999)080[2206:QVITSO]2.0.CO;2},
issn = {0012-9658},
year = {1999},
date = {1999-10-00},
journal = {Ecology},
volume = {80},
number = {7},
pages = {2206-2224},
abstract = {Understanding how the strengths of species interactions are distributed among species is critical for developing predictive models of natural food webs as well as for developing management and conservation strategies. Recently a number of ecologists have attempted to clarify the concepts of "strong-" and "weak-interactors" in a community, and to derive techniques for quantifying interaction strengths in the field, using metrics that are consistent, comparable, and of relevance to theoreticians. In this paper we examine potential biases in different empirical approaches to quantifying variation in interaction strengths within and among natural communities.
Using both simulated and published data, we explore the behavior of four commonly used or recently proposed empirical measures of the strength of consumer-prey interactions. The type of index used, the experimental protocol, and the underlying model of predator-prey interaction all strongly influence one's perception of both (1) the distribution of interaction strengths among species (e.g., presence of "keystone" species), and (2) the specific identity of the interactions that appear to be most important. Raw treatment differences tend to emphasize effects on very abundant prey, while the three proportional indices tend to emphasize effects on extremely rare prey. Two of the proportional indices are inherently asymmetric about zero, and they inflate positive or negative effects, respectively. When predators exhibit a saturating functional response, the three proportional measures of per capita effect are biased toward a skewed distribution of interaction strengths dominated by effects on the rarest prey. Predator interference causes the per capita measures to emphasize the effects of rare predators. Estimates of per capita effects are also problematic when (1) the per capita effects are back-calculated from experiments designed to measure collective effects (e.g., predator exclusions), and (2) the collective effect of a predator is constant across a wide range of predator densities, as may be common for keystone predators. Finally, since all of the indices show time-dependent behavior, they are differentially suited fur different experimental protocols (e.g., short-term vs, long-term results, or community initially near vs. far from equilibrium). All the indices explored here have the potential to provide useful, complementary information about ecological impacts of species in natural communities. In this analysis, we attempt to clarify what each index actually measures and the conditions under which each is most revealing.},
keywords = {density dependence, food web, functional response, interaction strength, keystone species, per capita effects, predator–prey interaction, simulation, species impact, species interactions},
pubstate = {published},
tppubtype = {article}
}
Understanding how the strengths of species interactions are distributed among species is critical for developing predictive models of natural food webs as well as for developing management and conservation strategies. Recently a number of ecologists have attempted to clarify the concepts of “strong-” and “weak-interactors” in a community, and to derive techniques for quantifying interaction strengths in the field, using metrics that are consistent, comparable, and of relevance to theoreticians. In this paper we examine potential biases in different empirical approaches to quantifying variation in interaction strengths within and among natural communities.
Using both simulated and published data, we explore the behavior of four commonly used or recently proposed empirical measures of the strength of consumer-prey interactions. The type of index used, the experimental protocol, and the underlying model of predator-prey interaction all strongly influence one’s perception of both (1) the distribution of interaction strengths among species (e.g., presence of “keystone” species), and (2) the specific identity of the interactions that appear to be most important. Raw treatment differences tend to emphasize effects on very abundant prey, while the three proportional indices tend to emphasize effects on extremely rare prey. Two of the proportional indices are inherently asymmetric about zero, and they inflate positive or negative effects, respectively. When predators exhibit a saturating functional response, the three proportional measures of per capita effect are biased toward a skewed distribution of interaction strengths dominated by effects on the rarest prey. Predator interference causes the per capita measures to emphasize the effects of rare predators. Estimates of per capita effects are also problematic when (1) the per capita effects are back-calculated from experiments designed to measure collective effects (e.g., predator exclusions), and (2) the collective effect of a predator is constant across a wide range of predator densities, as may be common for keystone predators. Finally, since all of the indices show time-dependent behavior, they are differentially suited fur different experimental protocols (e.g., short-term vs, long-term results, or community initially near vs. far from equilibrium). All the indices explored here have the potential to provide useful, complementary information about ecological impacts of species in natural communities. In this analysis, we attempt to clarify what each index actually measures and the conditions under which each is most revealing.
Using both simulated and published data, we explore the behavior of four commonly used or recently proposed empirical measures of the strength of consumer-prey interactions. The type of index used, the experimental protocol, and the underlying model of predator-prey interaction all strongly influence one’s perception of both (1) the distribution of interaction strengths among species (e.g., presence of “keystone” species), and (2) the specific identity of the interactions that appear to be most important. Raw treatment differences tend to emphasize effects on very abundant prey, while the three proportional indices tend to emphasize effects on extremely rare prey. Two of the proportional indices are inherently asymmetric about zero, and they inflate positive or negative effects, respectively. When predators exhibit a saturating functional response, the three proportional measures of per capita effect are biased toward a skewed distribution of interaction strengths dominated by effects on the rarest prey. Predator interference causes the per capita measures to emphasize the effects of rare predators. Estimates of per capita effects are also problematic when (1) the per capita effects are back-calculated from experiments designed to measure collective effects (e.g., predator exclusions), and (2) the collective effect of a predator is constant across a wide range of predator densities, as may be common for keystone predators. Finally, since all of the indices show time-dependent behavior, they are differentially suited fur different experimental protocols (e.g., short-term vs, long-term results, or community initially near vs. far from equilibrium). All the indices explored here have the potential to provide useful, complementary information about ecological impacts of species in natural communities. In this analysis, we attempt to clarify what each index actually measures and the conditions under which each is most revealing.
1996
Power, Mary E.; Tilman, David; Estes, James A.; Menge, Bruce A.; Bond, L. Scott Mills William J.; Daily, Gretchen; Castilla, Juan Carlos; Lubchenco, Jane; Paine, Robert T.
Challenges in the quest for keystones Journal Article
In: BioScience, vol. 46, no. 8, pp. 609-620, 1996, ISSN: 0006-3568, (File size exceeds Angelo maximum; see the stable link attached.).
Links | BibTeX | Tags: biological invasions, fish community, interaction strength, Lake Michigan, mass mortality, pocket gophers, river food webs, rocky intertidal community, sea otter predation, species concept
@article{Power1996b,
title = {Challenges in the quest for keystones},
author = {Mary E. Power and David Tilman and James A. Estes and Bruce A. Menge and L. Scott Mills William J. Bond and Gretchen Daily and Juan Carlos Castilla and Jane Lubchenco and Robert T. Paine},
url = {http://www.jstor.org/stable/1312990},
doi = {10.2307/1312990},
issn = {0006-3568},
year = {1996},
date = {1996-09-00},
journal = {BioScience},
volume = {46},
number = {8},
pages = {609-620},
note = {File size exceeds Angelo maximum; see the stable link attached.},
keywords = {biological invasions, fish community, interaction strength, Lake Michigan, mass mortality, pocket gophers, river food webs, rocky intertidal community, sea otter predation, species concept},
pubstate = {published},
tppubtype = {article}
}