Grazer behavior can regulate large-scale patterning of community states

AbstractEcosystem patterning can arise from environmental heterogeneity, biological feedbacks that produce multiple persistent ecological states, or their interaction. One source of feedbacks is density-dependent changes in behavior that regulates species interactions. By fitting dynamical models to large-scale (~500km) surveys on temperate rocky reefs, we find that behavioral feedbacks best explain why kelp and urchin barrens form either reef-wide patches or local mosaics. Best-supported models in California include feedbacks where starvation intensifies grazing across entire reefs create reef-scale, alternatively stable kelp- and urchin-dominated states (39% of sites). Best-fitting models in New Zealand include the feedback of urchins avoiding dense kelp stands that can increase abrasion and predation risk, which drives a transition from shallower urchin-dominated to deeper kelp-dominated zones, with patchiness at 3-8m depths with intermediate wave stress. Connecting locally-studied processes with region-wide data, we highlight how behavior can explain community patterning and why some systems exhibit community-wide alternative stable states.

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At what spatial scales are alternative stable states relevant in highly interconnected ecosystems?

10.1101/717504 ◽

2019 ◽

Cited By ~ 1

Author(s):

Vadim A. Karatayev ◽

Marissa L. Baskett

Keyword(s):

Spatial Scales ◽

Alternative Stable States ◽

Stable State ◽

Environmental Stochasticity ◽

Rocky Reef ◽

Alternative States ◽

Stable States ◽

Long Distance ◽

Rocky Reefs ◽

Model Predictions

AbstractWhether ecosystems recover from disturbance depends on the presence of alternative stable states, which are theoretically possible in simple models of many systems. However, definitive empirical evidence for this phenomenon remains limited to demographically closed ecosystems such as lakes. In more interconnected systems such as temperate rocky reefs, the local relevance of alternative stable states might erode as immigration overwhelms local feedbacks and produces a single stable state. At larger spatial scales, dispersal might counter localized disturbance and feedbacks to synchronize states throughout a region. Here, we quantify how interconnectedness affects the relevance of alternative stable states using dynamical models of California rocky reef communities that incorporate observed environmental stochasticity and feedback loops in kelp-urchin-predator interactions. Our models demonstrate the potential for localized alternative states despite high interconnectedness likely due to feedbacks affecting dispersers as they settle into local communities. Regionally, such feedbacks affecting settlement can produce a mosaic of alternative stable states that span local (10-20km) scales despite the synchronizing effect of long-distance dispersal. The specific spatial scale and duration of each state predominantly depend on the scales of environmental variation and on local dynamics (here, fishing). Model predictions reflect observed scales of community states in California rocky reefs and suggest how alternative states co-occur in the wide array of marine and terrestrial systems with settlement feedbacks.

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Untangling the complexity of priority effects in multi-species communities

10.1101/2021.03.29.437541 ◽

2021 ◽

Author(s):

Chuliang Song ◽

Tadashi Fukami ◽

Serguei Saavedra

Keyword(s):

Species Interactions ◽

Alternative Stable States ◽

Experimental Studies ◽

Theoretical Framework ◽

Priority Effects ◽

Ecological Communities ◽

Stable States ◽

Small Communities ◽

History Of ◽

Local Species

AbstractPriority effects arise when the history of species arrival influences local species interactions, thereby affecting the composition of ecological communities. The outcome of some priority effects may be more difficult to predict than others, but this possibility remains to be fully investigated. Here, we provide a graph-based, non-parametric, theoretical framework to understand the classification of priority effects and the predictability of multi-species communities. We show that we can classify priority effects by decomposing them into four basic dynamical sources: the number of alternative stable states, the number of alternative transient paths, the length of composition cycles, and the interaction between alternative stable states and composition cycles. Although the number of alternative stable states has received most of the attention, we show that the other three sources can contribute more to the predictability of community assembly, especially in small communities. We discuss how this theoretical framework can guide new experimental studies.

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Self-Organizing Processes in Landscape Pattern and Resilience: A Review

ISRN Ecology ◽

10.5402/2012/274510 ◽

2012 ◽

Vol 2012 ◽

pp. 1-18 ◽

Cited By ~ 2

Author(s):

Donald L. DeAngelis

Keyword(s):

Large Scale ◽

Alternative Stable States ◽

Bare Soil ◽

Landscape Patterns ◽

Vegetation Patterns ◽

Vegetation Types ◽

Stable States ◽

Common Basis ◽

Different Types ◽

Halophytic Plants

Environmental conditions influence the way different types of vegetation are distributed on various scales from the landscape to the globe. However, vegetation does not simply respond passively but may influence its environment in ways that shape those distributions. On the landscape scale, feedbacks from vegetation can lead to patterns that are not easily interpreted as merely reflecting external abiotic conditions. For example, sharp ecotones exist between two vegetation types, even if the basic abiotic gradient is slight, somewhere along the gradient. These are observed in transitions between numerous pairs of ecosystem types, such as tree/grassland, tree/mire, tree tundra, and halophytic plants/glycophytic plants. More complex spatial vegetation patterns may also exist, such as alternating stripes or irregular patterns of either two types of vegetation or vegetation and bare soil. One purpose of this paper is to emphasize that these two types of patterns, sharp ecotones between vegetation types and large-scale landscape patterns of vegetation, both have a common basis in the concept of bistability, in which alternative stable states can occur on an area of land. Another purpose is to note that an understanding of the basis of these patterns may ultimately help in management decisions.

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Floristic evidence for alternative biome states in tropical Africa

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2011515117 ◽

2020 ◽

Vol 117 (45) ◽

pp. 28183-28190

Author(s):

J. C. Aleman ◽

A. Fayolle ◽

C. Favier ◽

A. C. Staver ◽

K. G. Dexter ◽

...

Keyword(s):

Empirical Evidence ◽

Tree Species ◽

Large Scale ◽

Alternative Stable States ◽

Stable States ◽

Generalist Species ◽

Alternative Approach ◽

Species Lists ◽

Environmental Limits ◽

Structural Aspects

The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability.

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Species Diversity, Environmental Heterogeneity, and Species Interactions

Biodiversity in Drylands ◽

10.1093/oso/9780195139853.003.0009 ◽

2005 ◽

Author(s):

William A. Mitchell ◽

Burt P. Kotler

Keyword(s):

Species Interactions ◽

Large Scale ◽

Environmental Heterogeneity ◽

Species Coexistence ◽

Full Range ◽

Heterogeneous Environments ◽

Arid Environments ◽

Local Diversity ◽

Ecological Patterns ◽

Fitness Tradeoffs

Despite their apparent simplicity, arid environments can be quite heterogeneous. From small-scale variation in substrate and slope to large-scale geographic variation in solar input and productivity, drylands and deserts provide organisms with a tremendous range of ecological challenges (Schmidt-Nielsen 1964, Huggett 1995). Any single species is unable to meet all of these challenges equally well. A species will do better in some environments than others because evolution in heterogeneous environments is constrained by fitness tradeoffs. Such tradeoffs prevent the evolution of a versatile species, competitively superior to all other species across the entire spectrum of heterogeneity (Rosenzweig 1987). Although fitness tradeoffs may hinder species’ evolution in heterogeneous environments, they are a blessing for biodiversity. The source of biodiversity that we address in this chapter is the interplay of heterogeneity, tradeoffs, and density dependence. While we focus on species interactions at the local scale, our presentation includes a model that predicts changes in local diversity as a function of climate. The model’s predictions are based on changes in the nature of competition wrought by changes in productivity levels and climatic regimes. Cast in terms of evolutionary stable strategies (ESSs), the predictions refer to evolutionary as well as ecological patterns. A mechanism of coexistence consists of an axis of environmental heterogeneity together with an axis that indicates a tradeoff in the abilities of species to exploit different parts of the axis. In the absence of some kind of heterogeneity, there is only one environmental type, and whatever species is best adapted to it will competitively exclude others. In the absence of a tradeoff, one species could evolve competitive superiority over the full range of heterogeneity, again resulting in a monomorphic community. Consider some examples of mechanisms of species’ coexistence from dryland communities (Kotler and Brown 1988, Brown et al. 1994). For many taxa, spatial heterogeneity in predation risk is a consequence of the pattern of bushy and open areas common in drylands. In certain rodent communities, some species are able to exploit the relatively riskier open microhabitats by virtue of antipredator morphologies (Kotler 1984).

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Ecosystem context and historical contingency in apex predator recoveries

Science Advances ◽

10.1126/sciadv.1501769 ◽

2016 ◽

Vol 2 (5) ◽

pp. e1501769 ◽

Cited By ~ 32

Author(s):

Adrian C. Stier ◽

Jameal F. Samhouri ◽

Mark Novak ◽

Kristin N. Marshall ◽

Eric J. Ward ◽

...

Keyword(s):

Species Interactions ◽

Life Histories ◽

Restoration Ecology ◽

Alternative Stable States ◽

Unintended Consequences ◽

Apex Predator ◽

Historical Contingency ◽

Apex Predators ◽

Stable States ◽

Successful Recovery

Habitat loss, overexploitation, and numerous other stressors have caused global declines in apex predators. This “trophic downgrading” has generated widespread concern because of the fundamental role that apex predators can play in ecosystem functioning, disease regulation, and biodiversity maintenance. In attempts to combat declines, managers have conducted reintroductions, imposed stricter harvest regulations, and implemented protected areas. We suggest that full recovery of viable apex predator populations is currently the exception rather than the rule. We argue that, in addition to well-known considerations, such as continued exploitation and slow life histories, there are several underappreciated factors that complicate predator recoveries. These factors include three challenges. First, a priori identification of the suite of trophic interactions, such as resource limitation and competition that will influence recovery can be difficult. Second, defining and accomplishing predator recovery in the context of a dynamic ecosystem requires an appreciation of the timing of recovery, which can determine the relative density of apex predators and other predators and therefore affect competitive outcomes. Third, successful recovery programs require designing adaptive sequences of management strategies that embrace key environmental and species interactions as they emerge. Consideration of recent research on food web modules, alternative stable states, and community assembly offer important insights for predator recovery efforts and restoration ecology more generally. Foremost among these is the importance of a social-ecological perspective in facilitating a long-lasting predator restoration while avoiding unintended consequences.

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A shady phytoplankton paradox: when phytoplankton increases under low light

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.1067 ◽

2018 ◽

Vol 285 (1882) ◽

pp. 20181067 ◽

Cited By ~ 7

Author(s):

Masato Yamamichi ◽

Takehiro Kazama ◽

Kotaro Tokita ◽

Izumi Katano ◽

Hideyuki Doi ◽

...

Keyword(s):

Species Interactions ◽

Aquatic Ecosystems ◽

Nutrient Loading ◽

Scale Effects ◽

Harmful Algal Bloom ◽

Alternative Stable States ◽

Ecosystem Dynamics ◽

Light Limitation ◽

Phytoplankton Abundance ◽

Stable States

Light is a fundamental driver of ecosystem dynamics, affecting the rate of photosynthesis and primary production. In spite of its importance, less is known about its community-scale effects on aquatic ecosystems compared with those of nutrient loading. Understanding light limitation is also important for ecosystem management, as human activities have been rapidly altering light availability to aquatic ecosystems. Here we show that decreasing light can paradoxically increase phytoplankton abundance in shallow lakes. Our results, based on field manipulation experiments, field observations and models, suggest that, under competition for light and nutrients between phytoplankton and submersed macrophytes, alternative stable states are possible under high-light supply. In a macrophyte-dominated state, as light decreases phytoplankton density increases, because macrophytes (which effectively compete for nutrients released from the sediment) are more severely affected by light reduction. Our results demonstrate how species interactions with spatial heterogeneity can cause an unexpected outcome in complex ecosystems. An implication of our findings is that partial surface shading for controlling harmful algal bloom may, counterintuitively, increase phytoplankton abundance by decreasing macrophytes. Therefore, to predict how shallow lake ecosystems respond to environmental perturbations, it is essential to consider effects of light on the interactions between pelagic and benthic producers.

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Partnerships Generate Co-Benefits in Agricultural Stream Restoration (Canterbury, New Zealand)

Case Studies in the Environment ◽

10.1525/cse.2020.1229632 ◽

2020 ◽

Vol 4 (1) ◽

Author(s):

Catherine M. Febria ◽

Maggie Bayfield ◽

Kathryn E. Collins ◽

Hayley S. Devlin ◽

Brandon C. Goeller ◽

...

Keyword(s):

New Zealand ◽

Large Scale ◽

Agricultural Land ◽

Indigenous Rights ◽

Freshwater Ecosystem ◽

Reduced Pressure ◽

Ecosystem Integrity ◽

Riparian Management ◽

Scale Change ◽

Large Scale Change

In Aotearoa New Zealand, agricultural land-use intensification and decline in freshwater ecosystem integrity pose complex challenges for science and society. Despite riparian management programmes across the country, there is frustration over a lack in widespread uptake, upfront financial costs, possible loss in income, obstructive legislation and delays in ecological recovery. Thus, social, economic and institutional barriers exist when implementing and assessing agricultural freshwater restoration. Partnerships are essential to overcome such barriers by identifying and promoting co-benefits that result in amplifying individual efforts among stakeholder groups into coordinated, large-scale change. Here, we describe how initial progress by a sole farming family at the Silverstream in the Canterbury region, South Island, New Zealand, was used as a catalyst for change by the Canterbury Waterway Rehabilitation Experiment, a university-led restoration research project. Partners included farmers, researchers, government, industry, treaty partners (Indigenous rights-holders) and practitioners. Local capacity and capability was strengthened with practitioner groups, schools and the wider community. With partnerships in place, co-benefits included lowered costs involved with large-scale actions (e.g., earth moving), reduced pressure on individual farmers to undertake large-scale change (e.g., increased participation and engagement), while also legitimising the social contracts for farmers, scientists, government and industry to engage in farming and freshwater management. We describe contributions and benefits generated from the project and describe iterative actions that together built trust, leveraged and aligned opportunities. These actions were scaled from a single farm to multiple catchments nationally.

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