The effect of environmental stochasticity on species richness in neutral communities

Danino, Matan; Shnerb, Nadav M.; Azaele, Sandro; Kunin, William E.; Kessler, David A.

doi:10.1016/j.jtbi.2016.08.029

Cited by 51 publications

(94 citation statements)

References 34 publications

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“…From a different perspective, the ubiquitous presence of environmental stochasticity leads to attempts to incorporate it into the neutral model -one of the main theoretical frameworks in both population genetics and community ecology [12,14,16,17]. Biodiversity under neutral dynamics relays on speciation-absorption equilibrium, and as we have seen here, environmental stochasticity affects strongly the absorption rates.…”

Section: Discussionmentioning

confidence: 97%

“…The situations described so far correspond to the standard neutral model (perfect demographic equivalence, zero fitness differences between species and individuals) and to the time-averaged neutral model (TNTB) [16,17], where the species have the same fitness on average, but at each moment one species has higher fitness. In both cases, stochasticity (demographic or environmental) is the only driver of abundance variations.…”

Section: F the Interplay Between Stochasticity And Selectionmentioning

confidence: 99%

“…η i,j = 0 if i and j are conspecific individuals, η i,j = γ if i belongs to species 1 and j to species 2, η i,j = −γ if j ∈ 1 and i ∈ 2. Here we are interested in the situation of time averaged neutrality considered in [16,17,22], meaning that both species have the same average fitness but η fluctuates in time (environmental stochasticity). The simplest way to model such a scenario is to consider a dichotomous noise: the fitness parameter may take only two values, η = −η j,i = ±γ and after each elementary step the chance of the environment to stay in the same state is 1 − 1/τ , while the chance of the environment to flip (i.e, ±γ → ∓γ) is 1/τ .…”

Section: Environmental Stochasticity Without Storage Mechanismmentioning

confidence: 99%

“…The conditions under which this "storage effect" takes place, and its dependence on the system parameters, were considered by us in [17]. Here we would like to find the persistence time obtained from this dynamics.…”

Section: Environmental Stochasticity With Storage Effectmentioning

confidence: 99%

“…Based on this observation, a time-averaged neutral theory of biodiversity has been suggested [16,17], where environmental stochasticity affects the system but species are still symmetric since each species' fitness, when averaged over time, is identical. Again, species go extinct at a certain rate, now determined by both demographic and environmental stochasticity, and biodiversity reflects the balance between extinction and speciation/migration rates.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Stability of two-species communities: Drift, environmental stochasticity, storage effect and selection

Danino

Kessler

Shnerb

2018

Theoretical Population Biology

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The dynamics of two competing species in a finite size community is one of the most studied problems in population genetics and community ecology. Stochastic fluctuations lead, inevitably, to the extinction of one of the species, but the relevant timescale depends on the underlying dynamics. The persistence time of the community has been calculated for neutral models, where the only drive of the system is drift (demographic stochasticity) and for models with strong selection. Following recent analyses that stress the importance of environmental stochasticity in empirical systems, we present here a general theory of persistence time of two-species community where drift, environmental variations and time independent selective advantage are all taken into account.

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Section: Discussionmentioning

confidence: 97%

Section: F the Interplay Between Stochasticity And Selectionmentioning

confidence: 99%

Section: Environmental Stochasticity Without Storage Mechanismmentioning

confidence: 99%

Section: Environmental Stochasticity With Storage Effectmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Stability of two-species communities: Drift, environmental stochasticity, storage effect and selection

Danino

Kessler

Shnerb

2018

Theoretical Population Biology

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Reexamining the storage effect: Why temporal variation in abiotic factors seems unlikely to cause coexistence

Stump

Vasseur

2023

Ecological Monographs

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The temporal storage effect—that species coexist by partitioning abiotic niches that vary in time—is thought to be an important explanation for how species coexist. However, empirical studies that measure multiple mechanisms often find the storage effect is weak. We believe this mismatch is because of a shortcoming of theoretical models used to study the storage effect: that while the storage effect is described as having just three requirements (partitioning of temporal variation, buffered population growth, and a covariance between environment and density‐dependence), models used to study the storage effect make four assumptions, which are mathematically subtle but biologically important. In this paper, we examine those assumptions. First, models assume that environmental variation leads to a rapid impact on density‐dependence. We find that delays in density‐dependence (including delays caused by competition between cohorts) weaken the storage effect. Second, models assume that intraspecific competition is almost identical to interspecific competition. We find that unless resource or predator partitioning are virtually absent, then variation‐independent mechanisms will overshadow the benefits of the storage effect. Third, models assume even though there is vast variation in the environment, species are equally adapted on average (i.e., zero fitness‐differences). We show that fitness differences are particularly problematic in the storage effect because specializing on temporally rare niches is far less effective than specializing on other types of rare niches. Finally, models assume that stochastic extinctions can be ignored, and invader growth can determine coexistence. We show that storage effects tend to reduce mean persistence times, even if invader growth rates are positive. These results suggest that the assumptions needed for the storage effect are strict: if the first or second assumption is relaxed, it will greatly weaken the stabilizing mechanism; if the third or fourth assumption is relaxed, it will create a diversity‐destroying effect that may undermine coexistence. We examine three real‐world communities—annual plants, tropical forests, and iguanid lizards—and find that empirical studies suggest that all three communities violate multiple assumptions. This suggests that the temporal storage effect is probably not an important explanation for species diversity in most systems.

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Stochasticity‐induced stabilization in ecology and evolution: a new synthesis

Dean

Shnerb

2020

Ecology

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The ability of random environmental variation to stabilize competitor coexistence was pointed out long ago and, in recent years, has received considerable attention. Analyses have focused on variations in the log abundances of species, with mean logarithmic growth rates when rare, Er, used as metrics for persistence. However, invasion probabilities and the times to extinction are not single‐valued functions of Er and, in some cases, decrease as Er increases. Here, we present a synthesis of stochasticity‐induced stabilization (SIS) phenomena based on the ratio between the expected arithmetic growth normalμ and its variance g. When the diffusion approximation holds, explicit formulas for invasion probabilities and persistence times are single‐valued, monotonic functions of μ/g. The storage effect in the lottery model, together with other well‐known examples drawn from population genetics, microbiology, and ecology (including discrete and continuous dynamics, with overlapping and non‐overlapping generations), are placed together, reviewed, and explained within this new, transparent theoretical framework. We also clarify the relationships between life‐history strategies and SIS, and study the dynamics of extinction when SIS fails.

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The effect of environmental stochasticity on species richness in neutral communities

Cited by 51 publications

References 34 publications

Stability of two-species communities: Drift, environmental stochasticity, storage effect and selection

Stability of two-species communities: Drift, environmental stochasticity, storage effect and selection

Reexamining the storage effect: Why temporal variation in abiotic factors seems unlikely to cause coexistence

Stochasticity‐induced stabilization in ecology and evolution: a new synthesis

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