The surgeonfish Acanthurus lineatus grows hedgerows of Macroalgae

Robertson, D. Ross

doi:10.1007/bf00304686

Cited by 5 publications

(3 citation statements)

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“…Only rarely have models incorporated the effects of social behavior on herbivore distributions and dynamics (but see Seabloom and Reichman 2001). However, territoriality is a common social behavior that can have large impacts on the distribution of herbivores and their prey by creating refuges along the peripheries of adjacent territories (, Robertson 1989). In addition, by creating a zone of repulsion around each animal, territorial behavior lowers the maximum density of animals that can coexist (Vaughan 1967, Nevo 1979, Seabloom and Reichman 2001), and hence the maximum disturbance rate.…”

Section: Discussionmentioning

confidence: 99%

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Multiple Stable Equilibria in Grasslands Mediated by Herbivore Population Dynamics and Foraging Behavior

Seabloom

Richards

2003

Ecology

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Plant community structure is often the result of interactions between succession, disturbance, and dispersal. While some disturbances may be highly stochastic (e.g., flooding or landslides), other types of disturbance are closely linked to the current successional state of the community (e.g., fire or herbivory). For example, when herbivores preferentially feed on early successional species they may generate conditions favorable for these species and thus create a positive feedback. Positive feedbacks may create multiple stable equilibria within plant communities. We demonstrate the presence of these positive feedbacks using experiments conducted in a restored California grassland. We found that pocket gophers (Thomomys bottae) preferentially forage in areas dominated by annual species, and gopher foraging activity increases the abundance of annual plants. We use a Markov chain model to identify how the foraging behavior, dispersal behavior, and population dynamics of territorial herbivores can structure a plant community across multiple spatial scales. The model is loosely based on the biology of pocket gophers, though it is general enough to be applicable to other territorial herbivores with foraging preferences. We find that a foraging preference for early successional species can generate multiple plant communities that persist within a herbivore's territory. If juveniles are selective when searching for territories during their dispersal phase, then herbivores can also generate persistent and distinct plant communities over larger spatial scales. In this case, fixed regions of the landscape may become occupied by herbivores for long periods (many herbivore generations) and be composed of a range of successional plant species, whereas the remaining landscape is abandoned by herbivores and becomes dominated by late successional species. This structuring of the landscape occurs even though we assume that the entire landscape is intrinsically identical.

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Section: Discussionmentioning

confidence: 99%

“…On the other hand, if herbivores form territories, local biomass loss may be less rapid but spread over a large area. Social interactions that result in herbivores avoiding each other may create refuges for plants along the boundaries of adjacent territories (Robertson 1989, Seabloom and Reichman 2001).…”

Section: Introductionmentioning

confidence: 99%

Multiple Stable Equilibria in Grasslands Mediated by Herbivore Population Dynamics and Foraging Behavior

Seabloom

Richards

2003

Ecology

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“…Brawley and Adey (1977), Brock (1979) and other citations therein and in many parts of the world showed that herbivorous damselfish defend their territories against other herbivorous species, resulting in heavily grazed plant communities outside the territories with different physiognomy and species composition. Surgeonfish leave ungrazed 'hedgerows' of algae as buffer zones between their territories (Robertson 1989). There are numerous examples from marine environments where risk of predation on a herbivore constrains the herbivore's foraging of otherwise similar habitat, thereby influencing the risk of defoliation (Randall 1965, Ogden et al 1973, Hay et al 1983, Leber 1985, Irvine et al 1990, Stachowicz and Hay 1995, Stansfield et al 1995.…”

Section: Indirect A6oidancesmentioning

confidence: 99%

Grazing refuges, external avoidance of herbivory and plant diversity

Milchunas¹,

Noy‐Meir²

2002

Oikos

287

243

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Avoidance and tolerance are the two means by which plants cope with herbivores. Avoidances internal to the plant, such as morphology, chemical repellants, thorns, etc., have received considerable attention in the plant‐herbivore literature, but relatively little consideration has been given to avoidances external to the plant. We develop a conceptual framework of external plant avoidances of herbivory based on foraging selection impedances (associational avoidances), behavioral impedances (indirect avoidances), and physical impedances (refuges) organized along axes of efficiency, degree of protection, and necessity of tolerance characteristics. Associational avoidances are uncommon for terrestrial mammalian herbivores compared to plant‐insect or marine situations. Indirect avoidances mediated through herbivore territoriality, predator avoidance, and other behaviors independent of foraging decisions are probably common in nature, but few have been formally documented. Biotic and geologic refuges providing a physical impedance are the only avoidances shown to have implications for plant biodiversity. This is particularly true for geologic refuges, where there is not a tradeoff between competition and the refuge effect. Small geologic refuges (rock outcrops, cliffs, etc.) are more likely to also positively or negatively alter associated plant microenvironments than large geologic refuges (mesas, islands, etc.). In a survey, 86% of small refuge studies reported positive effects on plant diversity compared to 50% for large refuges. Geologic refuges in more productive environments were more important in protecting diversity than refuges in less productive, semiarid environments, and the effects of protection were greater in communities with short compared to long evolutionary histories of grazing. Other characteristics of refuges such as extent across the landscape and the manner they alter or ameliorate the environment, as well as characteristics of the herbivore such as small or large, generalist or specialist may also determine the effectiveness of refuges, but there are too few studies to assess these factors.

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