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Facilitative Effect of a Generalist Herbivore on the Recovery of a Perennial Alga: Consequences for Persistence at the Edge of Their Geographic Range.

Aguilera MA, Valdivia N, Broitman BR - PLoS ONE (2015)

Bottom Line: Here, we examined if consumptive effects of the intertidal grazer Scurria viridula positively influences the abundance and recovery from disturbances of the alga Mazzaella laminarioides at the edge of its geographic distributions in northern-central Chilean rocky shores.We found that S. viridula had positive net effects on M. laminarioides by increasing its cover and re-growth from perennial basal crusts.The negative effect of S. viridula on the percentage cover of opportunistic green algae-shown to compete for space with corticated algae-suggests that competitive release may be part of the mechanism driving the positive effect of the limpet on the abundance and recovery from disturbance of M. laminarioides.

View Article: PubMed Central - PubMed

Affiliation: Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Universidad Católica del Norte, Ossandón 877, Coquimbo, Chile.

ABSTRACT
Understanding the impacts of consumers on the abundance, growth rate, recovery and persistence of their resources across their distributional range can shed light on the role of trophic interactions in determining species range shifts. Here, we examined if consumptive effects of the intertidal grazer Scurria viridula positively influences the abundance and recovery from disturbances of the alga Mazzaella laminarioides at the edge of its geographic distributions in northern-central Chilean rocky shores. Through field experiments conducted at a site in the region where M. laminarioides overlaps with the polar range edge of S. viridula, we estimated the effects of grazing on different life stages of M. laminarioides. We also used long-term abundance surveys conducted across ~700 km of the shore to evaluate co-occurrence patterns of the study species across their range overlap. We found that S. viridula had positive net effects on M. laminarioides by increasing its cover and re-growth from perennial basal crusts. Probability of occurrence of M. laminarioides increased significantly with increasing density of S. viridula across the range overlap. The negative effect of S. viridula on the percentage cover of opportunistic green algae-shown to compete for space with corticated algae-suggests that competitive release may be part of the mechanism driving the positive effect of the limpet on the abundance and recovery from disturbance of M. laminarioides. We suggest that grazer populations contribute to enhance the abundance of M. laminarioides, facilitating its recolonization and persistence at its distributional range edge. Our study highlights that indirect facilitation can determine the recovery and persistence of a resource at the limit of its distribution, and may well contribute to the ecological mechanisms governing species distributions and range shifts.

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Related in: MedlinePlus

Predicted probability (± 95% CI) of occurrence of the corticated algae Mazzaella laminarioides determined by density of the grazer Scurria viridula found at four sites located within the range overlap estimated through logistic regressions.
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pone.0146069.g002: Predicted probability (± 95% CI) of occurrence of the corticated algae Mazzaella laminarioides determined by density of the grazer Scurria viridula found at four sites located within the range overlap estimated through logistic regressions.

Mentions: In order to estimate grazing intensity in experimental “open access areas” and to follow algal settlement, we measured every two months the density of herbivores and both adult and juvenile M. laminarioides in the experimental platforms (Fig 2A). The percentage cover of bare space in enclosure and control was considered as a direct measure of foraging rate of the focal grazer species in each experimental set compared with exclusions (grazer-free areas). Thus, this measure can be considered as a net effect of the focal grazer integrating positive indirect effect on M. laminarioides through foraging on competitors. Monthly from December 2009 to May 2010, we monitored the percentage cover of all macrobenthic (> 3 cm) sessile organisms occurring in each experimental area by means of 25 × 25 cm quadrats (81 uniformly spaced intersection points). At each sampling date, the whole benthic community in each plot was photographed with a high-resolution digital camera and percentage cover estimations were conducted in the laboratory. Monthly, we also measured the length of all M. laminarioides fronds re-grown from trimmed clumps. The area of each basal crust, and the number of fronds regrowth from them were measured at the end of the experiments.


Facilitative Effect of a Generalist Herbivore on the Recovery of a Perennial Alga: Consequences for Persistence at the Edge of Their Geographic Range.

Aguilera MA, Valdivia N, Broitman BR - PLoS ONE (2015)

Predicted probability (± 95% CI) of occurrence of the corticated algae Mazzaella laminarioides determined by density of the grazer Scurria viridula found at four sites located within the range overlap estimated through logistic regressions.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4696856&req=5

pone.0146069.g002: Predicted probability (± 95% CI) of occurrence of the corticated algae Mazzaella laminarioides determined by density of the grazer Scurria viridula found at four sites located within the range overlap estimated through logistic regressions.
Mentions: In order to estimate grazing intensity in experimental “open access areas” and to follow algal settlement, we measured every two months the density of herbivores and both adult and juvenile M. laminarioides in the experimental platforms (Fig 2A). The percentage cover of bare space in enclosure and control was considered as a direct measure of foraging rate of the focal grazer species in each experimental set compared with exclusions (grazer-free areas). Thus, this measure can be considered as a net effect of the focal grazer integrating positive indirect effect on M. laminarioides through foraging on competitors. Monthly from December 2009 to May 2010, we monitored the percentage cover of all macrobenthic (> 3 cm) sessile organisms occurring in each experimental area by means of 25 × 25 cm quadrats (81 uniformly spaced intersection points). At each sampling date, the whole benthic community in each plot was photographed with a high-resolution digital camera and percentage cover estimations were conducted in the laboratory. Monthly, we also measured the length of all M. laminarioides fronds re-grown from trimmed clumps. The area of each basal crust, and the number of fronds regrowth from them were measured at the end of the experiments.

Bottom Line: Here, we examined if consumptive effects of the intertidal grazer Scurria viridula positively influences the abundance and recovery from disturbances of the alga Mazzaella laminarioides at the edge of its geographic distributions in northern-central Chilean rocky shores.We found that S. viridula had positive net effects on M. laminarioides by increasing its cover and re-growth from perennial basal crusts.The negative effect of S. viridula on the percentage cover of opportunistic green algae-shown to compete for space with corticated algae-suggests that competitive release may be part of the mechanism driving the positive effect of the limpet on the abundance and recovery from disturbance of M. laminarioides.

View Article: PubMed Central - PubMed

Affiliation: Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Universidad Católica del Norte, Ossandón 877, Coquimbo, Chile.

ABSTRACT
Understanding the impacts of consumers on the abundance, growth rate, recovery and persistence of their resources across their distributional range can shed light on the role of trophic interactions in determining species range shifts. Here, we examined if consumptive effects of the intertidal grazer Scurria viridula positively influences the abundance and recovery from disturbances of the alga Mazzaella laminarioides at the edge of its geographic distributions in northern-central Chilean rocky shores. Through field experiments conducted at a site in the region where M. laminarioides overlaps with the polar range edge of S. viridula, we estimated the effects of grazing on different life stages of M. laminarioides. We also used long-term abundance surveys conducted across ~700 km of the shore to evaluate co-occurrence patterns of the study species across their range overlap. We found that S. viridula had positive net effects on M. laminarioides by increasing its cover and re-growth from perennial basal crusts. Probability of occurrence of M. laminarioides increased significantly with increasing density of S. viridula across the range overlap. The negative effect of S. viridula on the percentage cover of opportunistic green algae-shown to compete for space with corticated algae-suggests that competitive release may be part of the mechanism driving the positive effect of the limpet on the abundance and recovery from disturbance of M. laminarioides. We suggest that grazer populations contribute to enhance the abundance of M. laminarioides, facilitating its recolonization and persistence at its distributional range edge. Our study highlights that indirect facilitation can determine the recovery and persistence of a resource at the limit of its distribution, and may well contribute to the ecological mechanisms governing species distributions and range shifts.

Show MeSH
Related in: MedlinePlus