Grazing mosaics: Seascape attributes drive differences in herbivory in seagrass meadows
You can access the full text published in Functional Ecology or the pre-print version through Researchgate.
Even the simplest ecosystems exist as a patchwork of connected habitats forming a complex matrix through which animals have to navigate. The configuration of this mosaic can seriously affect both the number of species that can use the landscape, as well as their abundances. Some of these species may themselves be important actors in ecosystem processes, performing critical roles as herbivores or predators. By modifying how these species use the ecosystem, these landscape characteristics could have important implications for ecosystem functioning.
In our study, we looked at how differences in seagrass meadow mosaics could influence the way herbivory (a key process in these systems) was distributed across the landscape. Our principal herbivores were a mobile fish and a much less-mobile sea urchin. If these species were being influenced by the configuration of the patchwork, we hypothesised that differences in their interaction with landscape attributes would significantly influence herbivory rates.
To do this we measured rates of herbivory in seagrass patches that were embedded either in rocky substrates or on sand (the matrix attribute), close or far from rocky reefs (the distance attribute), and in the interior of meadows or at their edges (the edge attribute). We found that herbivory was higher in patches set in a rocky matrix compared to those on sand, and that the centres of meadows received higher rates of herbivory than their edges. These patterns were not influenced by the distance of the patches to rocky reefs. In itself this shows that landscape configurations can play an important role in determining how vital functions are distributed across the ecosystem.
To understand if herbivore numbers or food quality could explain these patterns, we measured herbivore abundances, seagrass production and plant quality in all the studied patches. Interestingly, the patches did not show significant differences in these variables. This suggests that the most likely reason for the patterns we recorded in herbivory lie in behavioural differences between species in their evaluation of risk, movement and food preference in relation to landscape configuration. Our results indicate that species richness and abundance patterns may not be sufficient to predict the impact of key species on the functioning of ecosystems within a mosaic of habitats.
Even the simplest ecosystems exist as a patchwork of connected habitats forming a complex matrix through which animals have to navigate. The configuration of this mosaic can seriously affect both the number of species that can use the landscape, as well as their abundances. Some of these species may themselves be important actors in ecosystem processes, performing critical roles as herbivores or predators. By modifying how these species use the ecosystem, these landscape characteristics could have important implications for ecosystem functioning.In our study, we looked at how differences in seagrass meadow mosaics could influence the way herbivory (a key process in these systems) was distributed across the landscape. Our principal herbivores were a mobile fish and a much less-mobile sea urchin. If these species were being influenced by the configuration of the patchwork, we hypothesised that differences in their interaction with landscape attributes would significantly influence herbivory rates.
To do this we measured rates of herbivory in seagrass patches that were embedded either in rocky substrates or on sand (the matrix attribute), close or far from rocky reefs (the distance attribute), and in the interior of meadows or at their edges (the edge attribute). We found that herbivory was higher in patches set in a rocky matrix compared to those on sand, and that the centres of meadows received higher rates of herbivory than their edges. These patterns were not influenced by the distance of the patches to rocky reefs. In itself this shows that landscape configurations can play an important role in determining how vital functions are distributed across the ecosystem.
To understand if herbivore numbers or food quality could explain these patterns, we measured herbivore abundances, seagrass production and plant quality in all the studied patches. Interestingly, the patches did not show significant differences in these variables. This suggests that the most likely reason for the patterns we recorded in herbivory lie in behavioural differences between species in their evaluation of risk, movement and food preference in relation to landscape configuration. Our results indicate that species richness and abundance patterns may not be sufficient to predict the impact of key species on the functioning of ecosystems within a mosaic of habitats.
