2003
Suttle, Kenwyn B.
Pollinators as mediators of top-down effects on plants Journal Article
In: Ecology Letters, vol. 6, no. 8, pp. 688-694, 2003.
Abstract | Links | BibTeX | Tags: Crab spider, indirect effects, interaction web, Leucanthemum vulgare, Misumenops schlingeri, ox-eye daisy, pollen limitation, pollination, predation, risk effects
@article{Suttle2003,
title = {Pollinators as mediators of top-down effects on plants},
author = {Kenwyn B. Suttle},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Suttle-2003-Ecology_Letters.pdf},
doi = {DOI: 10.1046/j.1461-0248.2003.00490.x},
year = {2003},
date = {2003-07-07},
journal = {Ecology Letters},
volume = {6},
number = {8},
pages = {688-694},
abstract = {This paper explores the idea that predators may disrupt plant–pollinator relationships and consequently inhibit reproduction in flowering plants. Amidst growing evidence that predators influence plant–pollinator interactions, I suggest that such pollinator-mediated indirect effects may be a common feature of terrestrial communities, with implications for research into top-down effects and pollination ecology. Experimental evidence of such an effect from a riparian system in northern California is provided, where crab spiders decreased seed production in inflorescences of the invasive plant Leucanthemum vulgare by reducing the frequency and duration of floral visits by pollinating insects.},
keywords = {Crab spider, indirect effects, interaction web, Leucanthemum vulgare, Misumenops schlingeri, ox-eye daisy, pollen limitation, pollination, predation, risk effects},
pubstate = {published},
tppubtype = {article}
}
This paper explores the idea that predators may disrupt plant–pollinator relationships and consequently inhibit reproduction in flowering plants. Amidst growing evidence that predators influence plant–pollinator interactions, I suggest that such pollinator-mediated indirect effects may be a common feature of terrestrial communities, with implications for research into top-down effects and pollination ecology. Experimental evidence of such an effect from a riparian system in northern California is provided, where crab spiders decreased seed production in inflorescences of the invasive plant Leucanthemum vulgare by reducing the frequency and duration of floral visits by pollinating insects.
2002
Sabo, John L.; Power, Mary E.
Numerical response of riparian lizards to aquatic insects and the short-term consequences for alternate terrestrial prey Journal Article
In: Ecology, vol. 83, no. 11, pp. 3023-3036, 2002.
Abstract | Links | BibTeX | Tags: Carabidae, food web, indirect effects, insect, lizard, Lycosidae, numerical response, Riparian, river–watershed exchange, Sceloporus occidentalis, subsidy, Western fence lizard
@article{Sabo2002e,
title = {Numerical response of riparian lizards to aquatic insects and the short-term consequences for alternate terrestrial prey},
author = {John L. Sabo and Mary E. Power},
url = {https://angelo.berkeley.edu/wp-content/uploads/sites/59/Numerical-response-of-riparian-lizards-to-aquatic-insects-and-the-short-term-consequences-for-alternate-terrestrial-prey_Sabo_2002.pdf},
doi = {10.2307/3071839},
year = {2002},
date = {2002-00-00},
journal = {Ecology},
volume = {83},
number = {11},
pages = {3023-3036},
abstract = {Spatial subsidies, or inputs of resources from more productive donor habitats, can cause numerical responses in consumer populations via behavioral and demographic mechanisms. In addition, subsidies may have indirect effects on the in situ prey of these consumers. These indirect effects can be either negative (e.g., apparent competition) or positive (e.g., via diet shifts) depending on the relative strength of the predator’s functional and numerical responses to prey subsidies. Here we report a numerical response by a lizard (Western fence lizard, Sceloporus occidentalis) to experimental reductions in the flux of river-derived insects. Initially, equal densities of lizards declined significantly faster in plots in which aquatic insect abundance was reduced by nearly 50% (season average) relative to controls. Abundance and biomass of terrestrial arthropods declined significantly between the start and end of the experiment across treatments. Despite consistently lower lizard abundance in plots with reduced subsidy levels, however, relative declines in the abundance and biomass of in situ terrestrial arthropods (all taxa combined) were not significantly different between reduced- and ambient-subsidy plots. Relative declines in spider biomass differed significantly between treatments and were higher in reduced-subsidy than ambient-subsidy plots, but only over one of three 3-wk sampling intervals. Thus, over the biologically active summer season, aquatic subsidies exerted brief positive or no significant indirect effects on the in situ prey of riparian lizards. These results suggest that, although aquatic insect prey may determine the spatial distribution and local abundance of riparian predators, the effects of increased predator density on in situ prey may be offset by higher per capita predation by these consumers on in situ prey in subsidy-poor relative to subsidy-rich habitats.
Numerical response of lizards to aquatic insects and short-term consequences for terrestrial prey.},
keywords = {Carabidae, food web, indirect effects, insect, lizard, Lycosidae, numerical response, Riparian, river–watershed exchange, Sceloporus occidentalis, subsidy, Western fence lizard},
pubstate = {published},
tppubtype = {article}
}
Spatial subsidies, or inputs of resources from more productive donor habitats, can cause numerical responses in consumer populations via behavioral and demographic mechanisms. In addition, subsidies may have indirect effects on the in situ prey of these consumers. These indirect effects can be either negative (e.g., apparent competition) or positive (e.g., via diet shifts) depending on the relative strength of the predator’s functional and numerical responses to prey subsidies. Here we report a numerical response by a lizard (Western fence lizard, Sceloporus occidentalis) to experimental reductions in the flux of river-derived insects. Initially, equal densities of lizards declined significantly faster in plots in which aquatic insect abundance was reduced by nearly 50% (season average) relative to controls. Abundance and biomass of terrestrial arthropods declined significantly between the start and end of the experiment across treatments. Despite consistently lower lizard abundance in plots with reduced subsidy levels, however, relative declines in the abundance and biomass of in situ terrestrial arthropods (all taxa combined) were not significantly different between reduced- and ambient-subsidy plots. Relative declines in spider biomass differed significantly between treatments and were higher in reduced-subsidy than ambient-subsidy plots, but only over one of three 3-wk sampling intervals. Thus, over the biologically active summer season, aquatic subsidies exerted brief positive or no significant indirect effects on the in situ prey of riparian lizards. These results suggest that, although aquatic insect prey may determine the spatial distribution and local abundance of riparian predators, the effects of increased predator density on in situ prey may be offset by higher per capita predation by these consumers on in situ prey in subsidy-poor relative to subsidy-rich habitats.
Numerical response of lizards to aquatic insects and short-term consequences for terrestrial prey.
Numerical response of lizards to aquatic insects and short-term consequences for terrestrial prey.
1999
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.
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.