Background/Question/Methods Biotic resistance refers to the joint negative effects of native comp... more Background/Question/Methods Biotic resistance refers to the joint negative effects of native competitors and enemies on exotic success. However, what strength of biotic resistance is meaningful, and the appropriate stage of invasion where it is best examined remains unresolved. One fruitful approach is to examine biotic resistance at the initial colonizing stages of invasion, where its significance can be tied to the degree to which biotic interactions limit colonization success, ultimate plant abundance, and impacts on community productivity. Taking this approach, in grasslands in western Montana we staged experimental invasions to examine how strongly competition from resident vegetation and rodent consumers influenced the abundance of added species. To contrast the effects of biotic filters on exotics versus natives, we added seeds of 19 species of exotics or natives to separate subplots that were either cleared of resident competitors or not and that were embedded in and outside...
Serpentine soils are considerably less invaded by alien species than nonserpentine soils in Calif... more Serpentine soils are considerably less invaded by alien species than nonserpentine soils in California’s North Coast Ranges. However, alien species are significantly more prevalent on small patches of serpentine (100 m from edges) of very large ones (>1 km2). We studied reasons for this pattern, focusing on the Mediterranean annual grasses Avena fatua L. and Bromus hordeaceus L. Using field transects, we
Background / Purpose: In a common garden experiment we tested the performance of giant goldenrod ... more Background / Purpose: In a common garden experiment we tested the performance of giant goldenrod ( Solidago gigantea ) grown from seeds collected from six populations in the native North American and six populations in the non-native European ranges. In a greenhouse experiment, we also tested whether the competitive ability of 15 native and invasive populations differed when matched against 11 common native North American competitors. Main conclusion: Our results suggest a rapid and biogeographically-based response in S. gigantea plants abroad, but a response that was environmentally and context dependent and that came at a strong cost to performance when reintroduced to the native range.
Empirical studies of spatial heterogeneity in parasitism by insect parasitoids have focused large... more Empirical studies of spatial heterogeneity in parasitism by insect parasitoids have focused largely on patterns, while the many possible underlying mechanisms have been little studied in the field. We conducted experimental and observational studies on Tachinomyia similis (Diptera: Tachinidae) attacking western tussock moths ( Orgyia vetusta; Lepidoptera: Lymantriidae) on lupine bushes at Bodega Bay, Calif., USA. We examined several foraging
Spatial patterns in population turnover were analyzed for five plant species confined to a patchy... more Spatial patterns in population turnover were analyzed for five plant species confined to a patchy and isolated habitat, serpentine seeps: annuals Helianthus exilis and Mimulus nudatus and perennials Senecio clevelandii , Astragalus clevelandii , and Delphinium uliginosum . A 3-year survey showed that, over a preceding 15-year period, 32 of 132 known populations in a 4200-ha area disappeared, and 65
Proceedings of the Royal Society B: Biological Sciences, 2006
Plants are attacked by many different consumers. A critical question is how often, and under what... more Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular consumers have predictably more or less influence on plant abundance, (ii) whether particular plant life-history types are predictably more vulnerable to herbivory at the population level, (iii) whether the strength of plant-consumer interactions shifts predictably across environmental gradients and (iv) the role of consumers in influencing plant distributional limits. Existing studies demonstrate numerous examples of consumers limiting local plant abundance and distribution. We found larger effects of consumers on grassland than woodland forbs, stronger effects of herbivory in areas with high versus low disturbance, but no systematic or unambiguous differences in the impact of consumers based on plant life-history or herbivore feeding mode. However, our ability to evaluate these and other patterns is limited by the small (but growing) number of studies in this area. As an impetus for further study, we review strengths and challenges of population-level studies, such as interpreting net impacts of consumers in the presence of density dependence and seed bank dynamics.
... Grosholz, Edwin D., Gregory M. Ruiz, Cheryl A. Dean, Kim A. Shirley, John L. Maron, and Peter... more ... Grosholz, Edwin D., Gregory M. Ruiz, Cheryl A. Dean, Kim A. Shirley, John L. Maron, and Peter G. Connors. 2000. ... Edwin D. Grosholz 1, 4 , Gregory M. Ruiz 2 , Cheryl A. Dean 3 , Kim A. Shirley 3 , John L. Maron 3 , and Peter G. Connors 3 ...
Background/Question/Methods Biotic resistance refers to the joint negative effects of native comp... more Background/Question/Methods Biotic resistance refers to the joint negative effects of native competitors and enemies on exotic success. However, what strength of biotic resistance is meaningful, and the appropriate stage of invasion where it is best examined remains unresolved. One fruitful approach is to examine biotic resistance at the initial colonizing stages of invasion, where its significance can be tied to the degree to which biotic interactions limit colonization success, ultimate plant abundance, and impacts on community productivity. Taking this approach, in grasslands in western Montana we staged experimental invasions to examine how strongly competition from resident vegetation and rodent consumers influenced the abundance of added species. To contrast the effects of biotic filters on exotics versus natives, we added seeds of 19 species of exotics or natives to separate subplots that were either cleared of resident competitors or not and that were embedded in and outside...
Serpentine soils are considerably less invaded by alien species than nonserpentine soils in Calif... more Serpentine soils are considerably less invaded by alien species than nonserpentine soils in California’s North Coast Ranges. However, alien species are significantly more prevalent on small patches of serpentine (100 m from edges) of very large ones (>1 km2). We studied reasons for this pattern, focusing on the Mediterranean annual grasses Avena fatua L. and Bromus hordeaceus L. Using field transects, we
Background / Purpose: In a common garden experiment we tested the performance of giant goldenrod ... more Background / Purpose: In a common garden experiment we tested the performance of giant goldenrod ( Solidago gigantea ) grown from seeds collected from six populations in the native North American and six populations in the non-native European ranges. In a greenhouse experiment, we also tested whether the competitive ability of 15 native and invasive populations differed when matched against 11 common native North American competitors. Main conclusion: Our results suggest a rapid and biogeographically-based response in S. gigantea plants abroad, but a response that was environmentally and context dependent and that came at a strong cost to performance when reintroduced to the native range.
Empirical studies of spatial heterogeneity in parasitism by insect parasitoids have focused large... more Empirical studies of spatial heterogeneity in parasitism by insect parasitoids have focused largely on patterns, while the many possible underlying mechanisms have been little studied in the field. We conducted experimental and observational studies on Tachinomyia similis (Diptera: Tachinidae) attacking western tussock moths ( Orgyia vetusta; Lepidoptera: Lymantriidae) on lupine bushes at Bodega Bay, Calif., USA. We examined several foraging
Spatial patterns in population turnover were analyzed for five plant species confined to a patchy... more Spatial patterns in population turnover were analyzed for five plant species confined to a patchy and isolated habitat, serpentine seeps: annuals Helianthus exilis and Mimulus nudatus and perennials Senecio clevelandii , Astragalus clevelandii , and Delphinium uliginosum . A 3-year survey showed that, over a preceding 15-year period, 32 of 132 known populations in a 4200-ha area disappeared, and 65
Proceedings of the Royal Society B: Biological Sciences, 2006
Plants are attacked by many different consumers. A critical question is how often, and under what... more Plants are attacked by many different consumers. A critical question is how often, and under what conditions, common reductions in growth, fecundity or even survival that occur due to herbivory translate to meaningful impacts on abundance, distribution or dynamics of plant populations. Here, we review population-level studies of the effects of consumers on plant dynamics and evaluate: (i) whether particular consumers have predictably more or less influence on plant abundance, (ii) whether particular plant life-history types are predictably more vulnerable to herbivory at the population level, (iii) whether the strength of plant-consumer interactions shifts predictably across environmental gradients and (iv) the role of consumers in influencing plant distributional limits. Existing studies demonstrate numerous examples of consumers limiting local plant abundance and distribution. We found larger effects of consumers on grassland than woodland forbs, stronger effects of herbivory in areas with high versus low disturbance, but no systematic or unambiguous differences in the impact of consumers based on plant life-history or herbivore feeding mode. However, our ability to evaluate these and other patterns is limited by the small (but growing) number of studies in this area. As an impetus for further study, we review strengths and challenges of population-level studies, such as interpreting net impacts of consumers in the presence of density dependence and seed bank dynamics.
... Grosholz, Edwin D., Gregory M. Ruiz, Cheryl A. Dean, Kim A. Shirley, John L. Maron, and Peter... more ... Grosholz, Edwin D., Gregory M. Ruiz, Cheryl A. Dean, Kim A. Shirley, John L. Maron, and Peter G. Connors. 2000. ... Edwin D. Grosholz 1, 4 , Gregory M. Ruiz 2 , Cheryl A. Dean 3 , Kim A. Shirley 3 , John L. Maron 3 , and Peter G. Connors 3 ...
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