2002
Sabo, John L.; Power, Mary E.
River-watershed exchange: Effects of riverine subsidies on riparian lizards and their terrestrial prey Journal Article
In: Ecology, vol. 83, no. 7, pp. 1860-1869, 2002, ISSN: 0012-9658.
Abstract | Links | BibTeX | Tags: APPARENT COMPETITION, AQUATIC INSECTS, BENTHIC-PELAGIC LINKS, COMMUNITIES, FOOD-WEB, invertebrates, ISLANDS, MARINE, SECONDARY PRODUCTION, STREAM
@article{Sabo2002,
title = {River-watershed exchange: Effects of riverine subsidies on riparian lizards and their terrestrial prey},
author = {John L. Sabo and Mary E. Power},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/River-watershed-exchange-Effects-of-riverine-subsidies-on-riparian-lizards-and-their-terrestrial-prey_Sabo_2002.pdf},
issn = {0012-9658},
year = {2002},
date = {2002-07-00},
journal = {Ecology},
volume = {83},
number = {7},
pages = {1860-1869},
abstract = {Resource subsidies from external habitats can enhance the performance or population density of local consumers, altering their effects on in situ prey. Indirect effects of subsidies may be either positive or negative depending on the behavior of the shared consumer. Here we document strong links between riverine insects, riparian lizards (Sceloporus occidentalis), and terrestrial invertebrates. We hypothesized that aquatic insects subsidize riparian lizard populations leading to higher growth rates of these lizards in near-river habitats, and that subsidies exert short-term positive effects on terrestrial resources as a result of diet shifts by lizards to aquatic insects. To test these hypotheses, we used 2 m high fences, or "subsidy shields," to experimentally reduce aquatic insect flux to large (91 m 2) enclosures of lizards. Subsidy shields reduced aquatic insect flux by 55-65%. Growth rates of lizards were 7X higher in subsidized (no-shield) enclosures during the early summer but were not significantly different later in the summer, when ambient fluxes of aquatic insects dropped to 20% of their early season levels. Within the watershed, lizard growth rates (in mass) were positively correlated with the numerical abundance of aquatic insects. Thus, lizard growth rates tracked both seasonal and spatial availability of riverine insect subsidies during our experiment. Subsidies also had indirect effects on the ground-dwelling, terrestrial prey of lizards. Declines of diurnal terrestrial invertebrates Were significantly higher in shield than no-shield enclosures, and the most common ground spider (Arctosa sp. [Lycosidae]) disappeared completely from shield enclosures by the end of the experiment. Declines in terrestrial invertebrate abundance did not differ between no-shield enclosures and lizard exclosures. These data suggest that riverine insects subsidize riparian Sceloporus and, in the short term, reduce their predation on terrestrial arthropods.},
keywords = {APPARENT COMPETITION, AQUATIC INSECTS, BENTHIC-PELAGIC LINKS, COMMUNITIES, FOOD-WEB, invertebrates, ISLANDS, MARINE, SECONDARY PRODUCTION, STREAM},
pubstate = {published},
tppubtype = {article}
}
Resource subsidies from external habitats can enhance the performance or population density of local consumers, altering their effects on in situ prey. Indirect effects of subsidies may be either positive or negative depending on the behavior of the shared consumer. Here we document strong links between riverine insects, riparian lizards (Sceloporus occidentalis), and terrestrial invertebrates. We hypothesized that aquatic insects subsidize riparian lizard populations leading to higher growth rates of these lizards in near-river habitats, and that subsidies exert short-term positive effects on terrestrial resources as a result of diet shifts by lizards to aquatic insects. To test these hypotheses, we used 2 m high fences, or “subsidy shields,” to experimentally reduce aquatic insect flux to large (91 m 2) enclosures of lizards. Subsidy shields reduced aquatic insect flux by 55-65%. Growth rates of lizards were 7X higher in subsidized (no-shield) enclosures during the early summer but were not significantly different later in the summer, when ambient fluxes of aquatic insects dropped to 20% of their early season levels. Within the watershed, lizard growth rates (in mass) were positively correlated with the numerical abundance of aquatic insects. Thus, lizard growth rates tracked both seasonal and spatial availability of riverine insect subsidies during our experiment. Subsidies also had indirect effects on the ground-dwelling, terrestrial prey of lizards. Declines of diurnal terrestrial invertebrates Were significantly higher in shield than no-shield enclosures, and the most common ground spider (Arctosa sp. [Lycosidae]) disappeared completely from shield enclosures by the end of the experiment. Declines in terrestrial invertebrate abundance did not differ between no-shield enclosures and lizard exclosures. These data suggest that riverine insects subsidize riparian Sceloporus and, in the short term, reduce their predation on terrestrial arthropods.
1999
Levine, Jonathan M.; D’Antonio, Carla M.
Elton revisited: a review of evidence linking diversity and invasibility Journal Article
In: Oikos, vol. 87, no. 1, pp. 15-26, 1999, ISSN: 0030-1299, (File size exceeds maximum allowable for Angelo’s website. Please see the attached stable link for PDF.).
Abstract | Links | BibTeX | Tags: biodiversity, biological invasions, California, COMMUNITIES, competition, exotic plants, grassland, introduced Hawaiian avifauna, New Zealand, positive interactions, riparian zones
@article{Levine1999,
title = {Elton revisited: a review of evidence linking diversity and invasibility},
author = {Jonathan M. Levine and Carla M. D'Antonio},
url = {http://www.jstor.org/stable/3546992},
doi = {10.2307/3546992},
issn = {0030-1299},
year = {1999},
date = {1999-10-00},
journal = {Oikos},
volume = {87},
number = {1},
pages = {15-26},
abstract = {It is commonly believed that diverse communities better resist invasion by exotic species than do simple communities. We examined the history of this notion, and evaluated theoretical and empirical work linking diversity and invasions. We found that much of the historical work that has contributed to the perception that diverse communities are less invasible, including Elton's observations and MacArthur's species-packing and diversity-stability models, is based on controversial premises. Nevertheless, more recent theoretical studies consistently supported the predicted negative relationship between diversity and invasibility. The results of empirical studies, however, were decidedly mixed. Constructed community studies directly manipulating diversity found both positive and negative effects of diversity on invasibility in both field and microcosm settings. Other empirical studies tracking the assembly of ecological communities generally suggested that communities decline in invasibility as species accumulate over time, though the role of diversity itself was often ambiguous. Studies of the spatial correlation between diversity and invasion and studies experimentally adding invaders to natural systems indicated that diverse communities tend to be more invasible. We argue that these results most likely reflect environmental factors spatially covarying with diversity in natural communities (e.g. resources, disturbance), and not the effects of diversity itself as uncovered by constructed community studies. Nevertheless, the consistent positive relationship between exotic species abundance and resident species diversity found in spatial pattern studies suggests that invaders and resident species are more similar than often believed, and the implications of this for theories of invasion are discussed.},
note = {File size exceeds maximum allowable for Angelo's website. Please see the attached stable link for PDF.},
keywords = {biodiversity, biological invasions, California, COMMUNITIES, competition, exotic plants, grassland, introduced Hawaiian avifauna, New Zealand, positive interactions, riparian zones},
pubstate = {published},
tppubtype = {article}
}
It is commonly believed that diverse communities better resist invasion by exotic species than do simple communities. We examined the history of this notion, and evaluated theoretical and empirical work linking diversity and invasions. We found that much of the historical work that has contributed to the perception that diverse communities are less invasible, including Elton’s observations and MacArthur’s species-packing and diversity-stability models, is based on controversial premises. Nevertheless, more recent theoretical studies consistently supported the predicted negative relationship between diversity and invasibility. The results of empirical studies, however, were decidedly mixed. Constructed community studies directly manipulating diversity found both positive and negative effects of diversity on invasibility in both field and microcosm settings. Other empirical studies tracking the assembly of ecological communities generally suggested that communities decline in invasibility as species accumulate over time, though the role of diversity itself was often ambiguous. Studies of the spatial correlation between diversity and invasion and studies experimentally adding invaders to natural systems indicated that diverse communities tend to be more invasible. We argue that these results most likely reflect environmental factors spatially covarying with diversity in natural communities (e.g. resources, disturbance), and not the effects of diversity itself as uncovered by constructed community studies. Nevertheless, the consistent positive relationship between exotic species abundance and resident species diversity found in spatial pattern studies suggests that invaders and resident species are more similar than often believed, and the implications of this for theories of invasion are discussed.
1988
Power, Mary E.; Stout, R. Jean; Cushing, Colbert E.; Harper, Peter P.; Hauer, F. Richard; Matthews, William J.; Moyle, Peter B.; Statzner, Bernhard; Badgen, Irene R. Wais De
Biotic and abiotic controls in river and stream communities Journal Article
In: Journal of the North American Benthological Society, vol. 7, no. 4, pp. 456-479, 1988.
Abstract | Links | BibTeX | Tags: algae, COMMUNITIES, discharge, disturbance., fish, life histories, rivers, streams, zoobenthos
@article{Power1988,
title = {Biotic and abiotic controls in river and stream communities},
author = {Mary E. Power and R. Jean Stout and Colbert E. Cushing and Peter P. Harper and F. Richard Hauer and William J. Matthews and Peter B. Moyle and Bernhard Statzner and Irene R. Wais De Badgen},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Power_1988_BenthoSoc.pdf},
doi = {10.2307/1467301},
year = {1988},
date = {1988-12-00},
journal = {Journal of the North American Benthological Society},
volume = {7},
number = {4},
pages = {456-479},
abstract = {Lotic ecologists share a major goal of explaining the distribution and abundance of biota in the world's rivers and streams, and of predicting how this biota will respond to change in fluvial ecosystems. We discuss five areas of research that would contribute to our pursuit of this goal. For mechanistic understanding of lotic community dynamics, we need more information on:
1. Physical conditions impinging on lotic biota, measured on temporal and spatial scales relevant to the organisms.
2. Responses of lotic biota to discharge fluctuations, including the processes that mediate community recovery following resets caused by spates or droughts.
3. Movements of lotic organisms that mediate gene flow, resource tracking, and multilevel species interactions.
4. Life history patterns, with special emphasis on ontogenetic bottlenecks that determine the vulnerability of populations confronting environmental perturbation.
5. Consequences of species interactions for community- and ecosystem-level processes in rivers and streams.
Without attempting to be comprehensive in our review, we discuss limits and limitations of our knowledge in these areas. We also suggest types of data and technological development that would advance our understanding. While we appreciate the value and need for empirical and comparative information, we advocate search for key mechanisms underlying community interactions as the crucial step toward developing general predictions of responses to environmental change. These mechanisms are likely to be complex, and elucidation of interacting bilateral, or multilateral, biotic and abiotic controls will progress only with the continuing synthesis of community- and ecosystem-level approaches in lotic ecology.},
keywords = {algae, COMMUNITIES, discharge, disturbance., fish, life histories, rivers, streams, zoobenthos},
pubstate = {published},
tppubtype = {article}
}
Lotic ecologists share a major goal of explaining the distribution and abundance of biota in the world’s rivers and streams, and of predicting how this biota will respond to change in fluvial ecosystems. We discuss five areas of research that would contribute to our pursuit of this goal. For mechanistic understanding of lotic community dynamics, we need more information on:
1. Physical conditions impinging on lotic biota, measured on temporal and spatial scales relevant to the organisms.
2. Responses of lotic biota to discharge fluctuations, including the processes that mediate community recovery following resets caused by spates or droughts.
3. Movements of lotic organisms that mediate gene flow, resource tracking, and multilevel species interactions.
4. Life history patterns, with special emphasis on ontogenetic bottlenecks that determine the vulnerability of populations confronting environmental perturbation.
5. Consequences of species interactions for community- and ecosystem-level processes in rivers and streams.
Without attempting to be comprehensive in our review, we discuss limits and limitations of our knowledge in these areas. We also suggest types of data and technological development that would advance our understanding. While we appreciate the value and need for empirical and comparative information, we advocate search for key mechanisms underlying community interactions as the crucial step toward developing general predictions of responses to environmental change. These mechanisms are likely to be complex, and elucidation of interacting bilateral, or multilateral, biotic and abiotic controls will progress only with the continuing synthesis of community- and ecosystem-level approaches in lotic ecology.
1. Physical conditions impinging on lotic biota, measured on temporal and spatial scales relevant to the organisms.
2. Responses of lotic biota to discharge fluctuations, including the processes that mediate community recovery following resets caused by spates or droughts.
3. Movements of lotic organisms that mediate gene flow, resource tracking, and multilevel species interactions.
4. Life history patterns, with special emphasis on ontogenetic bottlenecks that determine the vulnerability of populations confronting environmental perturbation.
5. Consequences of species interactions for community- and ecosystem-level processes in rivers and streams.
Without attempting to be comprehensive in our review, we discuss limits and limitations of our knowledge in these areas. We also suggest types of data and technological development that would advance our understanding. While we appreciate the value and need for empirical and comparative information, we advocate search for key mechanisms underlying community interactions as the crucial step toward developing general predictions of responses to environmental change. These mechanisms are likely to be complex, and elucidation of interacting bilateral, or multilateral, biotic and abiotic controls will progress only with the continuing synthesis of community- and ecosystem-level approaches in lotic ecology.