2007
McNeely, C.; Finlay, J. F.; Power, M. E.
Grazer traits, competition, and carbon sources to a headwater stream food web Journal Article
In: Ecology, vol. 88, no. 2, pp. 391-401, 2007.
Abstract | Links | BibTeX | Tags: carbon, competition, grazer
@article{McNeely2007b,
title = {Grazer traits, competition, and carbon sources to a headwater stream food web},
author = {C. McNeely and J. F. Finlay and M. E. Power},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/McNeely_2007_Ecology2.pdf},
doi = {10.1890/0012-9658(2007)88[391:GTCACS]2.0.CO;2},
year = {2007},
date = {2007-02-01},
journal = {Ecology},
volume = {88},
number = {2},
pages = {391-401},
abstract = {We investigated the effect of grazing by a dominant invertebrate grazer (the caddisfly Glossosoma penitum) on the energy sources used by other consumers in a headwater-stream food web. Stable isotope studies in small, forested streams in northern California have shown that G. penitum larvae derive most of their carbon from algae, despite low algal standing crops. We hypothesized that the caddisfly competes with other primary consumers (including mayflies) for algal food and increases their reliance on terrestrial detritus. Because Glossosoma are abundant and defended from predators by stone cases, their consumption of algal energy may reduce its transfer up the food chain. We removed Glossosoma (natural densities >1000 caddisflies/m2) from five approximately 4 m2) stream sections during the summer of 2000 and measured responses of algae, invertebrate primary consumers, and invertebrate predators. The treatment reduced Glossosoma biomass by 80-90%. We observed a doubling in chlorophyll a per area in sections with reduced Glossosoma abundance and aggregative increases in the biomass of undefended primary consumers. Heptageniid mayfly larvae consumed more algae (as measured by stable carbon isotope ratios and gut content analysis) in caddisfly removal plots at the end of the 60-day experiment, although not after one month. We did not see isotopic evidence of increased algal carbon in invertebrate predators, however. Patterns of caddisfly and mayfly diets in the surrounding watershed suggested that mayfly diets are variable and include algae and detrital carbon in variable proportions, but scraping caddisflies consume primarily algae. Caddisfly and mayfly diets are more similar in larger, more productive streams where the mayflies assimilate more algae. Isotopic analysis, in combination with measurements of macroinvertebrate abundance and biomass in unmanipulated plots, suggested that a substantial portion of the invertebrate community (>50% of biomass) was supported, at least partially, by local algal carbon during midsummer. These data suggest that algae may be more important to community dynamics in headwater streams than their relatively low productivity would suggest. Through their high densities and relative invulnerability to predation, armored grazers may also affect community structure and flow of algal and detrital carbon in headwater streams.},
keywords = {carbon, competition, grazer},
pubstate = {published},
tppubtype = {article}
}
We investigated the effect of grazing by a dominant invertebrate grazer (the caddisfly Glossosoma penitum) on the energy sources used by other consumers in a headwater-stream food web. Stable isotope studies in small, forested streams in northern California have shown that G. penitum larvae derive most of their carbon from algae, despite low algal standing crops. We hypothesized that the caddisfly competes with other primary consumers (including mayflies) for algal food and increases their reliance on terrestrial detritus. Because Glossosoma are abundant and defended from predators by stone cases, their consumption of algal energy may reduce its transfer up the food chain. We removed Glossosoma (natural densities >1000 caddisflies/m2) from five approximately 4 m2) stream sections during the summer of 2000 and measured responses of algae, invertebrate primary consumers, and invertebrate predators. The treatment reduced Glossosoma biomass by 80-90%. We observed a doubling in chlorophyll a per area in sections with reduced Glossosoma abundance and aggregative increases in the biomass of undefended primary consumers. Heptageniid mayfly larvae consumed more algae (as measured by stable carbon isotope ratios and gut content analysis) in caddisfly removal plots at the end of the 60-day experiment, although not after one month. We did not see isotopic evidence of increased algal carbon in invertebrate predators, however. Patterns of caddisfly and mayfly diets in the surrounding watershed suggested that mayfly diets are variable and include algae and detrital carbon in variable proportions, but scraping caddisflies consume primarily algae. Caddisfly and mayfly diets are more similar in larger, more productive streams where the mayflies assimilate more algae. Isotopic analysis, in combination with measurements of macroinvertebrate abundance and biomass in unmanipulated plots, suggested that a substantial portion of the invertebrate community (>50% of biomass) was supported, at least partially, by local algal carbon during midsummer. These data suggest that algae may be more important to community dynamics in headwater streams than their relatively low productivity would suggest. Through their high densities and relative invulnerability to predation, armored grazers may also affect community structure and flow of algal and detrital carbon in headwater streams.
Thomsen, M. A.; D’Antonio, C. M.
In: Oikos, vol. 116, no. 1, pp. 17-30, 2007.
Abstract | Links | BibTeX | Tags: competition, grassland, invasion
@article{Thomsen2007,
title = {Mechanisms of resistance to invasion in a California grassland: the roles of competitor identity, resource availability, and environmental gradients},
author = {M. A. Thomsen and C. M. D'Antonio},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Thomsen_2007_Oikos.pdf},
doi = {10.1111/j.2006.0030-1299.14929.x},
year = {2007},
date = {2007-01-01},
journal = {Oikos},
volume = {116},
number = {1},
pages = {17-30},
abstract = {Resistance to the invasion of exotic plants may sometimes result from the strong effects of a relatively small number of resident species. Understanding the mechanisms by which such species resist invasion could provide important insights for the management of invaded ecosystems. Furthermore, the individualistic responses of community members to resource availability and environmental gradients could drive spatial variation in resistance at the local to landscape scales. We tested the resistance of monoculture plots of three native perennial grasses from the California coastal prairie to the invasion of the European perennial grass Holcus lanatus. We also used a watering treatment that increased early summer water availability and a natural elevational gradient in resource availability and soil texture to evaluate how resident identity interacted with abiotic resistance to affect Holcus establishment. Two native species, Festuca rubra and Calamagrostis nutkaensis, exhibited strong resistance, correlated with their negative effects on light availability. A third native grass, Bromus carinatus var. maritimus, had either no effect or a weakly facultative effect on Holcus performance relative to bare plots. Water addition did not alter the resistance of these species, but the elevation gradient did. Holcus invasion increased with improving abiotic conditions towards the slope bottom in bare and Bromus plots, but invasion decreased towards the bottom in Calamagrostis plots, where better conditions favored competitive residents. These results support the idea that resistance to invasion can sometimes be due to a subset of native species, and that the resistance provided by even a single species is likely to vary across the landscape. Identifying the mechanisms by which species resist invasion could facilitate the selection of management strategies that at best increase, or at worst do not decrease, natural resistance.},
keywords = {competition, grassland, invasion},
pubstate = {published},
tppubtype = {article}
}
Resistance to the invasion of exotic plants may sometimes result from the strong effects of a relatively small number of resident species. Understanding the mechanisms by which such species resist invasion could provide important insights for the management of invaded ecosystems. Furthermore, the individualistic responses of community members to resource availability and environmental gradients could drive spatial variation in resistance at the local to landscape scales. We tested the resistance of monoculture plots of three native perennial grasses from the California coastal prairie to the invasion of the European perennial grass Holcus lanatus. We also used a watering treatment that increased early summer water availability and a natural elevational gradient in resource availability and soil texture to evaluate how resident identity interacted with abiotic resistance to affect Holcus establishment. Two native species, Festuca rubra and Calamagrostis nutkaensis, exhibited strong resistance, correlated with their negative effects on light availability. A third native grass, Bromus carinatus var. maritimus, had either no effect or a weakly facultative effect on Holcus performance relative to bare plots. Water addition did not alter the resistance of these species, but the elevation gradient did. Holcus invasion increased with improving abiotic conditions towards the slope bottom in bare and Bromus plots, but invasion decreased towards the bottom in Calamagrostis plots, where better conditions favored competitive residents. These results support the idea that resistance to invasion can sometimes be due to a subset of native species, and that the resistance provided by even a single species is likely to vary across the landscape. Identifying the mechanisms by which species resist invasion could facilitate the selection of management strategies that at best increase, or at worst do not decrease, natural resistance.
2006
Thomsen, M. A.; D’Antonio, C. M.; Suttle, K. B.; Sousa, W. P.
Ecological resistance, seed density and their interactions determine patterns of invasion in a California coastal grassland Journal Article
In: Ecology Letters, vol. 9, no. 2, pp. 160-170, 2006.
Abstract | Links | BibTeX | Tags: Climate, competition, exotic, invasibility, Mediterranean, propagule supply, wateravailability
@article{Thomsen2006,
title = {Ecological resistance, seed density and their interactions determine patterns of invasion in a California coastal grassland},
author = {M. A. Thomsen and C. M. D'Antonio and K. B. Suttle and W. P. Sousa},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Thomsen_2006_EcoLetters.pdf},
doi = {10.1111/j.1461-0248.2005.00857.x},
year = {2006},
date = {2006-02-01},
journal = {Ecology Letters},
volume = {9},
number = {2},
pages = {160-170},
abstract = {Relatively little experimental evidence is available regarding how ecological resistance and propagule density interact in their effects on the establishment of invasive exotic species. We examined the independent and interactive effects of neighbour cover (biotic resistance), winter vs. spring water addition (abiotic resistance) and seed density on the invasion of the European perennial grass Holcus lanatus into a California coastal grassland dominated by exotic annual grasses. We found that decreased competition from resident exotic grasses had no effect. In contrast, increased late-season water availability eroded the abiotic resistance offered by naturally dry conditions, facilitating invasion. Finally, watering treatment and seed density interacted strongly in determining seedling survival: while seedling mortality was close to 100% in ambient and winter water addition plots, survivor numbers increased with seed density in spring-watered plots. Thus, decreased abiotic resistance can amplify the effect of increased propagule density on seedling establishment, thereby increasing the likelihood of invasion.},
keywords = {Climate, competition, exotic, invasibility, Mediterranean, propagule supply, wateravailability},
pubstate = {published},
tppubtype = {article}
}
Relatively little experimental evidence is available regarding how ecological resistance and propagule density interact in their effects on the establishment of invasive exotic species. We examined the independent and interactive effects of neighbour cover (biotic resistance), winter vs. spring water addition (abiotic resistance) and seed density on the invasion of the European perennial grass Holcus lanatus into a California coastal grassland dominated by exotic annual grasses. We found that decreased competition from resident exotic grasses had no effect. In contrast, increased late-season water availability eroded the abiotic resistance offered by naturally dry conditions, facilitating invasion. Finally, watering treatment and seed density interacted strongly in determining seedling survival: while seedling mortality was close to 100% in ambient and winter water addition plots, survivor numbers increased with seed density in spring-watered plots. Thus, decreased abiotic resistance can amplify the effect of increased propagule density on seedling establishment, thereby increasing the likelihood of invasion.
2001
Hunter, John C.; Barbour, Michael G.
Through-growth by Pseudotsuga menziesii: A mechanism for change in forest composition without canopy gaps Journal Article
In: Journal of Vegetation Science, vol. 12, no. 4, pp. 445-452, 2001, ISSN: 1100-9233.
Abstract | Links | BibTeX | Tags: acer-saccharum, competition, disturbance, light, morphology, northern California, patterns, recruitment, stands, trees
@article{Hunter2001,
title = {Through-growth by Pseudotsuga menziesii: A mechanism for change in forest composition without canopy gaps},
author = {John C. Hunter and Michael G. Barbour},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Through-Growth-by-Pseudotsuga-menziesii-A-Mechanism-for-Change-in-Forest-Composition-without-Canopy-Gaps_Hunter_Barbour_2001.pdf},
doi = {10.2307/3236996},
issn = {1100-9233},
year = {2001},
date = {2001-08-00},
journal = {Journal of Vegetation Science},
volume = {12},
number = {4},
pages = {445-452},
abstract = {exception. In California's Pseudotsuga-mixed hardwood forests, crowns of Pseudotsuga menziesii (Douglas fir) are within those of angiosperm trees (Arbutus menziesii and Quercus species). In the forests we examined, every Pseudotsuga was younger and all but one were growing more rapidly in girth than the Arbutus or Quercus whose crown it had penetrated. Furthermore, as saplings. the Pseudotsuga had grown at rates between those of suppressed saplings and canopy dominants, The recruitment of emergent Pseudotsuga substantially alters these canopies because of the large size Pseudotsuga attains. Given the density of Pseudotsuga growing in canopy crowns, such recruitment is likely. As a mechanism of recruitment, this through-growth differs from gap recruitment in that the turnover of canopy trees is determined by an understory species' growth rate rather than the overstory species' longevity, and community attributes may change rapidly by replacement of canopy dominants with a dissimilar species. Pseudotsuga could grow through the canopy because of its greater potential height (> 60m vs. 20-40m for the angio-perms). narrower crown and its branches suffering less mechanical damage than those of the angiosperms. In general, resource levels in the understory, canopy height, and interspecific differences in maximum height and crown architecture all influence the likelihood of through-growth. Therefore, for vegetation types whose dominants differ substantially in growth form, through-growth may be a mechanism for rapid ecosystem change.},
keywords = {acer-saccharum, competition, disturbance, light, morphology, northern California, patterns, recruitment, stands, trees},
pubstate = {published},
tppubtype = {article}
}
exception. In California’s Pseudotsuga-mixed hardwood forests, crowns of Pseudotsuga menziesii (Douglas fir) are within those of angiosperm trees (Arbutus menziesii and Quercus species). In the forests we examined, every Pseudotsuga was younger and all but one were growing more rapidly in girth than the Arbutus or Quercus whose crown it had penetrated. Furthermore, as saplings. the Pseudotsuga had grown at rates between those of suppressed saplings and canopy dominants, The recruitment of emergent Pseudotsuga substantially alters these canopies because of the large size Pseudotsuga attains. Given the density of Pseudotsuga growing in canopy crowns, such recruitment is likely. As a mechanism of recruitment, this through-growth differs from gap recruitment in that the turnover of canopy trees is determined by an understory species’ growth rate rather than the overstory species’ longevity, and community attributes may change rapidly by replacement of canopy dominants with a dissimilar species. Pseudotsuga could grow through the canopy because of its greater potential height (> 60m vs. 20-40m for the angio-perms). narrower crown and its branches suffering less mechanical damage than those of the angiosperms. In general, resource levels in the understory, canopy height, and interspecific differences in maximum height and crown architecture all influence the likelihood of through-growth. Therefore, for vegetation types whose dominants differ substantially in growth form, through-growth may be a mechanism for rapid ecosystem change.
d’Antonio, Carla; Levine, Jonathan; Thomsen, Meredith
Ecosystem resistance to invasion and the role of propagule supply: a California perspective Journal Article
In: International Journal of Mediterranean Ecology, vol. 27, pp. 233-245, 2001.
Abstract | Links | BibTeX | Tags: alien species, competition, disturbance, exotic invaders, non-indigenous plants.
@article{d'Antonio2001,
title = {Ecosystem resistance to invasion and the role of propagule supply: a California perspective},
author = {Carla d'Antonio and Jonathan Levine and Meredith Thomsen},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/dantonio_levine_thomsen_2001.pdf},
year = {2001},
date = {2001-00-00},
journal = {International Journal of Mediterranean Ecology},
volume = {27},
pages = {233-245},
abstract = {The concept of ecological resistance includes both abiotic and biotic features of a recipient environment that influence the success of propagules of a species that has not previously occurred on a site. Despite broad interest in this topic by ecologists and land managers, we lack an understanding of what factors contribute to ecological resistance and how processes influencing resistance interact with the supply of propagules to determine invasion success. Here we present a simple conceptual framework for examining how variation in propagule supply should interact with ecosystem resistance to influence the rate at which exotic invaders enter a habitat. We suggest that when resistance is low, it takes very few propagules for an invader to become established and that rates of invasion will be fast regardless of propagule supply. As resistance increases, however, it takes proportionally more propagules for the invader to establish. When resistance is high invasion will occur only when propagule pressure is high or when invaders themselves can alter resistance as they get a toehold in the community. When resistance is controlled largely by biotic factors we believe that it can be overcome by high rates of propagule supply even if initially appears to be strong, because over space and time biological sources of resistance are likely to be variable allowing windows when a site has moved to a region of the propagule supply axis where many fewer propagules are required for invasion to occur. By contrast, strong abiotic resistance is less likely to be overwhelmed by high propagule pressure and if determined largely by soil factors, is likely to be relatively constant over space and time. We also suggest, that some invaders of harsh environments are successful because of their own ability to modify abiotic conditions thus decreasing the number of propagules needed to promote further invasion. We review examples of resistance in California plant communities and where possible show how resistance interacts with propagule supply. Overall, we found very few studies that measure or consider the role of propagule supply and how it interacts with resistance factors and we believe that such studies are badly needed if we are to advance our understanding of controls over biological invasion.},
keywords = {alien species, competition, disturbance, exotic invaders, non-indigenous plants.},
pubstate = {published},
tppubtype = {article}
}
The concept of ecological resistance includes both abiotic and biotic features of a recipient environment that influence the success of propagules of a species that has not previously occurred on a site. Despite broad interest in this topic by ecologists and land managers, we lack an understanding of what factors contribute to ecological resistance and how processes influencing resistance interact with the supply of propagules to determine invasion success. Here we present a simple conceptual framework for examining how variation in propagule supply should interact with ecosystem resistance to influence the rate at which exotic invaders enter a habitat. We suggest that when resistance is low, it takes very few propagules for an invader to become established and that rates of invasion will be fast regardless of propagule supply. As resistance increases, however, it takes proportionally more propagules for the invader to establish. When resistance is high invasion will occur only when propagule pressure is high or when invaders themselves can alter resistance as they get a toehold in the community. When resistance is controlled largely by biotic factors we believe that it can be overcome by high rates of propagule supply even if initially appears to be strong, because over space and time biological sources of resistance are likely to be variable allowing windows when a site has moved to a region of the propagule supply axis where many fewer propagules are required for invasion to occur. By contrast, strong abiotic resistance is less likely to be overwhelmed by high propagule pressure and if determined largely by soil factors, is likely to be relatively constant over space and time. We also suggest, that some invaders of harsh environments are successful because of their own ability to modify abiotic conditions thus decreasing the number of propagules needed to promote further invasion. We review examples of resistance in California plant communities and where possible show how resistance interacts with propagule supply. Overall, we found very few studies that measure or consider the role of propagule supply and how it interacts with resistance factors and we believe that such studies are badly needed if we are to advance our understanding of controls over biological invasion.
2000
Levine, Jonathan M.
Complex interactions in a streamside plant community Journal Article
In: Ecology, vol. 81, no. 12, pp. 3431-3444, 2000, ISSN: 0012-9658.
Abstract | Links | BibTeX | Tags: associational defense, Carex, competition, facilitation, Junonia, Mimulus, riparian community
@article{Levine2000,
title = {Complex interactions in a streamside plant community},
author = {Jonathan M. Levine},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Complex-interactions-in-a-streamside-plant-community_Levine_2000.pdf},
doi = {10.1890/0012-9658(2000)081[3431:CIIASP]2.0.CO;2},
issn = {0012-9658},
year = {2000},
date = {2000-12-00},
journal = {Ecology},
volume = {81},
number = {12},
pages = {3431-3444},
abstract = {Ecologists are increasingly finding that complex combinations of competitive and facilitative interactions influence the distribution and abundance of plants. I conducted a two-year field experiment to explore these processes in a streamside community lining the South Fork Eel River in northern California. Specifically, I tested the hypothesis that the sedge Carex nudata provides critical stable substrate for other plants during winter floods and protection from herbivores over the growing season. In addition to these facilitative effects, Carer is also hypothesized to compete with the associated species, and thus limit their size and reproduction.
To evaluate these hypotheses, I followed the performance of transplanted individuals of Mimulus guttatus, M. cardinalis, Juncus covillei, Conocephalum conicum, and Brachythecium frigidum and naturally occurring individuals of Epipactis gigantea on Carer tussocks with dense, thinned, pinned back, or completely clipped Carer stems. The five transplanted species were also planted directly onto the emergent streambed. Though streambed transplants grew as well as those on tussocks over the summer, they experienced significantly greater winter mortality, up to 100%, supporting the hypothesis that tussocks provide a critical stable substrate. In contrast, growing season competition by Carer reduced biomass by over 50% for five of the six species and reduced reproductive performance by over 60%. Also, over the growing season, Carex protected M. guttatus and Epipactis from insect larvae and deer, respectively, reducing herbivory by >75%. Additional results from a deer exclosure treatment showed that the positive effects of this "associational defense" were equal in magnitude to the negative effects of Carer competition on Epipactis biomass. The mechanisms underlying these associational defenses and the implications of my results for the relationship between disturbance and facilitation are discussed. I suggest that regarding plant interactions as combinations of facilitative and competitive components may enhance our understanding of natural communities.},
keywords = {associational defense, Carex, competition, facilitation, Junonia, Mimulus, riparian community},
pubstate = {published},
tppubtype = {article}
}
Ecologists are increasingly finding that complex combinations of competitive and facilitative interactions influence the distribution and abundance of plants. I conducted a two-year field experiment to explore these processes in a streamside community lining the South Fork Eel River in northern California. Specifically, I tested the hypothesis that the sedge Carex nudata provides critical stable substrate for other plants during winter floods and protection from herbivores over the growing season. In addition to these facilitative effects, Carer is also hypothesized to compete with the associated species, and thus limit their size and reproduction.
To evaluate these hypotheses, I followed the performance of transplanted individuals of Mimulus guttatus, M. cardinalis, Juncus covillei, Conocephalum conicum, and Brachythecium frigidum and naturally occurring individuals of Epipactis gigantea on Carer tussocks with dense, thinned, pinned back, or completely clipped Carer stems. The five transplanted species were also planted directly onto the emergent streambed. Though streambed transplants grew as well as those on tussocks over the summer, they experienced significantly greater winter mortality, up to 100%, supporting the hypothesis that tussocks provide a critical stable substrate. In contrast, growing season competition by Carer reduced biomass by over 50% for five of the six species and reduced reproductive performance by over 60%. Also, over the growing season, Carex protected M. guttatus and Epipactis from insect larvae and deer, respectively, reducing herbivory by >75%. Additional results from a deer exclosure treatment showed that the positive effects of this “associational defense” were equal in magnitude to the negative effects of Carer competition on Epipactis biomass. The mechanisms underlying these associational defenses and the implications of my results for the relationship between disturbance and facilitation are discussed. I suggest that regarding plant interactions as combinations of facilitative and competitive components may enhance our understanding of natural communities.
To evaluate these hypotheses, I followed the performance of transplanted individuals of Mimulus guttatus, M. cardinalis, Juncus covillei, Conocephalum conicum, and Brachythecium frigidum and naturally occurring individuals of Epipactis gigantea on Carer tussocks with dense, thinned, pinned back, or completely clipped Carer stems. The five transplanted species were also planted directly onto the emergent streambed. Though streambed transplants grew as well as those on tussocks over the summer, they experienced significantly greater winter mortality, up to 100%, supporting the hypothesis that tussocks provide a critical stable substrate. In contrast, growing season competition by Carer reduced biomass by over 50% for five of the six species and reduced reproductive performance by over 60%. Also, over the growing season, Carex protected M. guttatus and Epipactis from insect larvae and deer, respectively, reducing herbivory by >75%. Additional results from a deer exclosure treatment showed that the positive effects of this “associational defense” were equal in magnitude to the negative effects of Carer competition on Epipactis biomass. The mechanisms underlying these associational defenses and the implications of my results for the relationship between disturbance and facilitation are discussed. I suggest that regarding plant interactions as combinations of facilitative and competitive components may enhance our understanding of natural communities.
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.
Levine, Jonathan M.
Indirect facilitation: evidence and predictions from a riparian community Journal Article
In: Ecology, vol. 80, no. 5, pp. 1762-1769, 1999, ISSN: 0012-9658.
Abstract | Links | BibTeX | Tags: Carex, competition, facilitation, facilitation in plant communities, indirect effects, Mimulus, plant competition, riparian plant communities, species diversity
@article{Levine1999b,
title = {Indirect facilitation: evidence and predictions from a riparian community},
author = {Jonathan M. Levine},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Indirect-facilitation-evidence-and-predictions-from-a-riparian-community_Levine_1999.pdf},
doi = {10.1890/0012-9658(1999)080[1762:IFEAPF]2.0.CO;2},
issn = {0012-9658},
year = {1999},
date = {1999-07-00},
journal = {Ecology},
volume = {80},
number = {5},
pages = {1762-1769},
abstract = {Indirect facilitation occurs when the indirect positive effect of one species on another, via the suppression of a shared competitor, is stronger than the direct competitive effect. Although theory predicts that these interactions may be common in assemblages of three or more competitors, experimental studies of this process are rare. Here, I report a study of a northern California riparian community, where I tested the hypothesis that the sedge Carex nudata had direct competitive effects on other plant species, as well as indirect facilitative effects, by suppressing a second competitor, the common monkey-flower Mimulus guttatus. Results of a field experiment, in which I manipulated the presence of Cares and M. guttatus in a factorial design, uncovered three qualitatively different interactions between Carer and three target species. I found evidence of indirect facilitation for the liverwort Conocephalum conicum, such that Carex "facilitated" Conocephalum in the presence of M. guttatus, while Carer competed with Conocephalum in the absence of M. guttatus. Plant distribution patterns supported the widespread occurrence of this interaction. Carer also had an indirect positive effect on the scarlet monkey-flower M. cardinalis, though the magnitude of this effect was similar to direct Carex competition. Lastly, Carex had no influence on the moss Brachythecium frigidum. The mechanisms underlying the plant interactions in this study are discussed and incorporated into a general hypothesis that indirect facilitation among competitors is most important in assemblages of species that vary in competitive mechanism.},
keywords = {Carex, competition, facilitation, facilitation in plant communities, indirect effects, Mimulus, plant competition, riparian plant communities, species diversity},
pubstate = {published},
tppubtype = {article}
}
Indirect facilitation occurs when the indirect positive effect of one species on another, via the suppression of a shared competitor, is stronger than the direct competitive effect. Although theory predicts that these interactions may be common in assemblages of three or more competitors, experimental studies of this process are rare. Here, I report a study of a northern California riparian community, where I tested the hypothesis that the sedge Carex nudata had direct competitive effects on other plant species, as well as indirect facilitative effects, by suppressing a second competitor, the common monkey-flower Mimulus guttatus. Results of a field experiment, in which I manipulated the presence of Cares and M. guttatus in a factorial design, uncovered three qualitatively different interactions between Carer and three target species. I found evidence of indirect facilitation for the liverwort Conocephalum conicum, such that Carex “facilitated” Conocephalum in the presence of M. guttatus, while Carer competed with Conocephalum in the absence of M. guttatus. Plant distribution patterns supported the widespread occurrence of this interaction. Carer also had an indirect positive effect on the scarlet monkey-flower M. cardinalis, though the magnitude of this effect was similar to direct Carex competition. Lastly, Carex had no influence on the moss Brachythecium frigidum. The mechanisms underlying the plant interactions in this study are discussed and incorporated into a general hypothesis that indirect facilitation among competitors is most important in assemblages of species that vary in competitive mechanism.
1997
Kupferberg, Sarah J.
Facilitation of periphyton production by tadpole grazing: functional differences between species Journal Article
In: Freshwater Biology, vol. 37, no. 2, pp. 427-439, 1997.
Abstract | Links | BibTeX | Tags: AQUATIC INSECTS, bottom-up, competition, epiphytes, food webs, herbivores, nutrient, stream periphyton, top-down, trophic cascades
@article{Kupferberg1997c,
title = {Facilitation of periphyton production by tadpole grazing: functional differences between species},
author = {Sarah J. Kupferberg},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/KUPFERBERG_Freshwater_Biology1997.pdf},
year = {1997},
date = {1997-04-00},
journal = {Freshwater Biology},
volume = {37},
number = {2},
pages = {427-439},
abstract = {1. This study examined how interactions between resources that vary in edibility, and herbivores that vary in ability to acquire resources, control primary productivity. In a northern California river, grazing on Cladophora glomerata, a relatively inedible filamentous green alga, and its more nutritious epiphytic diatoms, was manipulated by exposing cobbles to tadpoles (Rana boylii or Hyla regilla) or excluding tadpoles.
2. Rana indirectly facilitated Cladophora by removing diatoms, whereas Hyla did not significantly change biomass relative to controls. Algal ash-free dry mass on cobbles in Rana treatments was 65 and 72% greater than on controls in two years of investigation (1991 and 1993). Rana decreased epiphytic diatom biovolume by 56% and detritus by 87%.
3. Because nitrogen excretion rates of Hyla and Rana were similar, the differences in effect between the two species were probably due to their roles as consumers rather than as recyclers.
4. The net effect of Rana on periphyton was a 10% increase in areal specific primary productivity (mg O-2 h(-1) m(-2)); Hyla caused an 18% decrease. Rana decreased biomass-specific productivity (mg O-2 h(-1) g(-1)) 44%; Hyla had no effect.
5. In tadpole exclosures, grazers such as baetid mayfly larvae (mostly Centroptilum sp.) were 4.7 (1991) and 1.8 (1993) times more abundant, and midge larvae (Chironomidae) were 2.5 (1991) and 2 (1993) times more abundant than in Rana enclosures. Invertebrate assemblages in Hyla enclosures, however, were similar to exclosures. Few predatory insects and fish colonized Rana enclosures. Path analyses indicated that Rana affected macroinvertebrates via both interference and exploitation of epiphytic diatoms.},
keywords = {AQUATIC INSECTS, bottom-up, competition, epiphytes, food webs, herbivores, nutrient, stream periphyton, top-down, trophic cascades},
pubstate = {published},
tppubtype = {article}
}
1. This study examined how interactions between resources that vary in edibility, and herbivores that vary in ability to acquire resources, control primary productivity. In a northern California river, grazing on Cladophora glomerata, a relatively inedible filamentous green alga, and its more nutritious epiphytic diatoms, was manipulated by exposing cobbles to tadpoles (Rana boylii or Hyla regilla) or excluding tadpoles.
2. Rana indirectly facilitated Cladophora by removing diatoms, whereas Hyla did not significantly change biomass relative to controls. Algal ash-free dry mass on cobbles in Rana treatments was 65 and 72% greater than on controls in two years of investigation (1991 and 1993). Rana decreased epiphytic diatom biovolume by 56% and detritus by 87%.
3. Because nitrogen excretion rates of Hyla and Rana were similar, the differences in effect between the two species were probably due to their roles as consumers rather than as recyclers.
4. The net effect of Rana on periphyton was a 10% increase in areal specific primary productivity (mg O-2 h(-1) m(-2)); Hyla caused an 18% decrease. Rana decreased biomass-specific productivity (mg O-2 h(-1) g(-1)) 44%; Hyla had no effect.
5. In tadpole exclosures, grazers such as baetid mayfly larvae (mostly Centroptilum sp.) were 4.7 (1991) and 1.8 (1993) times more abundant, and midge larvae (Chironomidae) were 2.5 (1991) and 2 (1993) times more abundant than in Rana enclosures. Invertebrate assemblages in Hyla enclosures, however, were similar to exclosures. Few predatory insects and fish colonized Rana enclosures. Path analyses indicated that Rana affected macroinvertebrates via both interference and exploitation of epiphytic diatoms.
2. Rana indirectly facilitated Cladophora by removing diatoms, whereas Hyla did not significantly change biomass relative to controls. Algal ash-free dry mass on cobbles in Rana treatments was 65 and 72% greater than on controls in two years of investigation (1991 and 1993). Rana decreased epiphytic diatom biovolume by 56% and detritus by 87%.
3. Because nitrogen excretion rates of Hyla and Rana were similar, the differences in effect between the two species were probably due to their roles as consumers rather than as recyclers.
4. The net effect of Rana on periphyton was a 10% increase in areal specific primary productivity (mg O-2 h(-1) m(-2)); Hyla caused an 18% decrease. Rana decreased biomass-specific productivity (mg O-2 h(-1) g(-1)) 44%; Hyla had no effect.
5. In tadpole exclosures, grazers such as baetid mayfly larvae (mostly Centroptilum sp.) were 4.7 (1991) and 1.8 (1993) times more abundant, and midge larvae (Chironomidae) were 2.5 (1991) and 2 (1993) times more abundant than in Rana enclosures. Invertebrate assemblages in Hyla enclosures, however, were similar to exclosures. Few predatory insects and fish colonized Rana enclosures. Path analyses indicated that Rana affected macroinvertebrates via both interference and exploitation of epiphytic diatoms.
1987
Hill, W. R.; Knight, A. W.
Experimental analysis of the grazing interaction between a mayfly and stream algae Journal Article
In: Ecology, vol. 68, no. 6, pp. 1955-1965, 1987.
Abstract | Links | BibTeX | Tags: algae, Ameletus, assemblage structure, competition, diatoms, grazing, indirect effects, mayfly, periphyton, standing crop, streams
@article{Hill1987,
title = {Experimental analysis of the grazing interaction between a mayfly and stream algae},
author = {W. R. Hill and A. W. Knight},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Hill_1987_Eco.pdf},
doi = {10.2307/1939886},
year = {1987},
date = {1987-12-01},
journal = {Ecology},
volume = {68},
number = {6},
pages = {1955-1965},
abstract = {The interaction between the grazing mayfly Ameletus validus and periphyton in a small, northern California stream was examined by manipulating the density of the mayfly in flow—through plexiglass channels. Containing natural cobble substrate and located in situ, the channels established an initial gradient of A. validus at 0, 0.5, 1, and 4 times the average density of the mayfly in Barnwell Creek. After 23 d, A. validus significantly depressed periphyton standing crop: ash—free dry mass (AFDM) at the 0, 0.5, 1, and 4 N grazer densities was 5.067 ± 1.389 (se), 1.829 ± 0.173, 1.741 ± 0.325, and 1.009 ± 0.199 g/m2 (ANOVA: P < .01). The mayfly also influenced two structural attributes of the periphyton, increasing the amount of chlorophyll a per unit biomass and decreasing the relative contribution of the loose, upper layer to total periphyton biomass. Principal component analysis of algal relative abundances contrasted the effect of grazing on two groups of diatoms. A group of species found primarily in the loose layer of periphyton (Nitzschia spp., Surirella spiralis, Cymatopleura elliptica, and Navicula cryptocephala) was disproportionately reduced in abundance, while an adnate group (Gomphonema clevei, Achnanthes minutissima, Synedra ulna, Rhoicosphenia curvata, and an undescribed species of Epithemia) increased its relative abundance with increasing grazing pressure. The decline in relative abundance of the loose layer diatoms did not appear to result from selective consumption by A. validus, but may have been mediated by a reduction of inorganic sediment in the periphyton by A. validus. Inorganic sediment was highly correlated with the relative abundances of the loose layer group of diatoms, a group of species that are adapted for locomotion on sediment substrates. A. validus growth in the experimental channels was strongly density dependent. Growth in length over 23 d for the 0.5, 1, and 4 N treatments was 2.24 ± 0.17, 1.80 ± 0.23, and 1.15 ± 0.25 mm (ANOVA: P < .01). The significantly greater growth of A. validus at subnormal densities in the experimental channels suggested that the A. validus population in Barnwell Creek was food—limited.},
keywords = {algae, Ameletus, assemblage structure, competition, diatoms, grazing, indirect effects, mayfly, periphyton, standing crop, streams},
pubstate = {published},
tppubtype = {article}
}
The interaction between the grazing mayfly Ameletus validus and periphyton in a small, northern California stream was examined by manipulating the density of the mayfly in flow—through plexiglass channels. Containing natural cobble substrate and located in situ, the channels established an initial gradient of A. validus at 0, 0.5, 1, and 4 times the average density of the mayfly in Barnwell Creek. After 23 d, A. validus significantly depressed periphyton standing crop: ash—free dry mass (AFDM) at the 0, 0.5, 1, and 4 N grazer densities was 5.067 ± 1.389 (se), 1.829 ± 0.173, 1.741 ± 0.325, and 1.009 ± 0.199 g/m2 (ANOVA: P < .01). The mayfly also influenced two structural attributes of the periphyton, increasing the amount of chlorophyll a per unit biomass and decreasing the relative contribution of the loose, upper layer to total periphyton biomass. Principal component analysis of algal relative abundances contrasted the effect of grazing on two groups of diatoms. A group of species found primarily in the loose layer of periphyton (Nitzschia spp., Surirella spiralis, Cymatopleura elliptica, and Navicula cryptocephala) was disproportionately reduced in abundance, while an adnate group (Gomphonema clevei, Achnanthes minutissima, Synedra ulna, Rhoicosphenia curvata, and an undescribed species of Epithemia) increased its relative abundance with increasing grazing pressure. The decline in relative abundance of the loose layer diatoms did not appear to result from selective consumption by A. validus, but may have been mediated by a reduction of inorganic sediment in the periphyton by A. validus. Inorganic sediment was highly correlated with the relative abundances of the loose layer group of diatoms, a group of species that are adapted for locomotion on sediment substrates. A. validus growth in the experimental channels was strongly density dependent. Growth in length over 23 d for the 0.5, 1, and 4 N treatments was 2.24 ± 0.17, 1.80 ± 0.23, and 1.15 ± 0.25 mm (ANOVA: P < .01). The significantly greater growth of A. validus at subnormal densities in the experimental channels suggested that the A. validus population in Barnwell Creek was food—limited.