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Christian Smit - One of the best experts on this subject based on the ideXlab platform.
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nurse plants tree saplings and grazing pressure changes in facilitation along a biotic Environmental Gradient
Oecologia, 2007Co-Authors: Christian Smit, Charlotte Vandenberghe, Jan Den Ouden, Heinz MullerscharerAbstract:Current conceptual models predict that an increase in stress shifts interactions between plants from competitive to facilitative; hence, facilitation is expected to gain in ecological importance with increasing stress. Little is known about how facilitative interactions between plants change with increasing biotic stress, such as that incurred by consumer pressure or herbivory (i.e. disturbance sensu Grime). In grazed ecosystems, the presence of unpalatable plants is reported to protect tree saplings against cattle grazing and enhance tree establishment. In accordance with current conceptual facilitation-stress models, we hypothesised a positive relationship between facilitation and grazing pressure. We tested this hypothesis in a field experiment in which tree saplings of four different species (deciduous Fagus sylvatica, Acer pseudoplatanus and coniferous Abies alba, Picea abies) were planted either inside or outside of the canopy of the spiny nurse shrub Rosa rubiginosa in enclosures differing in grazing pressure (low and high) and in exclosures. During one grazing season we followed the survival of the different tree saplings and the level of browsing on these; we also estimated browsing damage to the nurse shrubs. Shrub damage was highest at the higher grazing pressure. Correspondingly, browsing increased and survival decreased in saplings located inside the canopy of the shrubs at the high grazing pressure compared to the low grazing pressure. Saplings of both deciduous species showed a higher survival than the evergreens, while sapling browsing did not differ between species. The relative facilitation of sapling browsing and sapling survival – i.e. the difference between saplings inside and outside the shrub canopy – decreased at high grazing pressure as the facilitative species became less protective. Interestingly, these findings do not agree with current conceptual facilitation-stress models predicting increasing facilitation with abiotic stress. We used our results to design a conceptual model of facilitation along a biotic Environmental Gradient. Empirical studies are needed to test the applicability of this model. In conclusion, we suggest that current conceptual facilitation models should at least consider the possibility of decreasing facilitation at high levels of stress.
Remi Mattheydoret - One of the best experts on this subject based on the ideXlab platform.
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local adaptation interacts with expansion load during range expansion maladaptation reduces expansion load
The American Naturalist, 2017Co-Authors: Kimberly J Gilbert, Amy L Angert, Nathaniel P Sharp, Gina L Conte, Jeremy A Draghi, Frederic Guillaume, Anna L Hargreaves, Remi MattheydoretAbstract:AbstractThe biotic and abiotic factors that facilitate or hinder species range expansions are many and complex. We examine the impact of two genetic processes and their interaction on fitness at expanding range edges: local maladaptation resulting from the presence of an Environmental Gradient and expansion load resulting from increased genetic drift at the range edge. Results from spatially explicit simulations indicate that the presence of an Environmental Gradient during range expansion reduces expansion load; conversely, increasing expansion load allows only locally adapted populations to persist at the range edge. Increased maladaptation reduces the speed of range expansion, resulting in less genetic drift at the expanding front and more immigration from the range center, therefore reducing expansion load at the range edge. These results may have ramifications for species being forced to shift their ranges because of climate change or other anthropogenic changes. If rapidly changing climate leads to ...
Heinz Mullerscharer - One of the best experts on this subject based on the ideXlab platform.
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nurse plants tree saplings and grazing pressure changes in facilitation along a biotic Environmental Gradient
Oecologia, 2007Co-Authors: Christian Smit, Charlotte Vandenberghe, Jan Den Ouden, Heinz MullerscharerAbstract:Current conceptual models predict that an increase in stress shifts interactions between plants from competitive to facilitative; hence, facilitation is expected to gain in ecological importance with increasing stress. Little is known about how facilitative interactions between plants change with increasing biotic stress, such as that incurred by consumer pressure or herbivory (i.e. disturbance sensu Grime). In grazed ecosystems, the presence of unpalatable plants is reported to protect tree saplings against cattle grazing and enhance tree establishment. In accordance with current conceptual facilitation-stress models, we hypothesised a positive relationship between facilitation and grazing pressure. We tested this hypothesis in a field experiment in which tree saplings of four different species (deciduous Fagus sylvatica, Acer pseudoplatanus and coniferous Abies alba, Picea abies) were planted either inside or outside of the canopy of the spiny nurse shrub Rosa rubiginosa in enclosures differing in grazing pressure (low and high) and in exclosures. During one grazing season we followed the survival of the different tree saplings and the level of browsing on these; we also estimated browsing damage to the nurse shrubs. Shrub damage was highest at the higher grazing pressure. Correspondingly, browsing increased and survival decreased in saplings located inside the canopy of the shrubs at the high grazing pressure compared to the low grazing pressure. Saplings of both deciduous species showed a higher survival than the evergreens, while sapling browsing did not differ between species. The relative facilitation of sapling browsing and sapling survival – i.e. the difference between saplings inside and outside the shrub canopy – decreased at high grazing pressure as the facilitative species became less protective. Interestingly, these findings do not agree with current conceptual facilitation-stress models predicting increasing facilitation with abiotic stress. We used our results to design a conceptual model of facilitation along a biotic Environmental Gradient. Empirical studies are needed to test the applicability of this model. In conclusion, we suggest that current conceptual facilitation models should at least consider the possibility of decreasing facilitation at high levels of stress.
Jeremy A Draghi - One of the best experts on this subject based on the ideXlab platform.
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local adaptation interacts with expansion load during range expansion maladaptation reduces expansion load
The American Naturalist, 2017Co-Authors: Kimberly J Gilbert, Amy L Angert, Nathaniel P Sharp, Gina L Conte, Jeremy A Draghi, Frederic Guillaume, Anna L Hargreaves, Remi MattheydoretAbstract:AbstractThe biotic and abiotic factors that facilitate or hinder species range expansions are many and complex. We examine the impact of two genetic processes and their interaction on fitness at expanding range edges: local maladaptation resulting from the presence of an Environmental Gradient and expansion load resulting from increased genetic drift at the range edge. Results from spatially explicit simulations indicate that the presence of an Environmental Gradient during range expansion reduces expansion load; conversely, increasing expansion load allows only locally adapted populations to persist at the range edge. Increased maladaptation reduces the speed of range expansion, resulting in less genetic drift at the expanding front and more immigration from the range center, therefore reducing expansion load at the range edge. These results may have ramifications for species being forced to shift their ranges because of climate change or other anthropogenic changes. If rapidly changing climate leads to ...
Anna L Hargreaves - One of the best experts on this subject based on the ideXlab platform.
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local adaptation interacts with expansion load during range expansion maladaptation reduces expansion load
The American Naturalist, 2017Co-Authors: Kimberly J Gilbert, Amy L Angert, Nathaniel P Sharp, Gina L Conte, Jeremy A Draghi, Frederic Guillaume, Anna L Hargreaves, Remi MattheydoretAbstract:AbstractThe biotic and abiotic factors that facilitate or hinder species range expansions are many and complex. We examine the impact of two genetic processes and their interaction on fitness at expanding range edges: local maladaptation resulting from the presence of an Environmental Gradient and expansion load resulting from increased genetic drift at the range edge. Results from spatially explicit simulations indicate that the presence of an Environmental Gradient during range expansion reduces expansion load; conversely, increasing expansion load allows only locally adapted populations to persist at the range edge. Increased maladaptation reduces the speed of range expansion, resulting in less genetic drift at the expanding front and more immigration from the range center, therefore reducing expansion load at the range edge. These results may have ramifications for species being forced to shift their ranges because of climate change or other anthropogenic changes. If rapidly changing climate leads to ...