1. In many grassland communities, the identity of dominant speciesmay be determined by initial frequency owing to priority effects. Yet, the conditions for these priority effects remain unclear. 2. Focusing on interactions between annual and perennial plants, we used a simulation model to investigate how longevity, fecundity, and the competitive ability of seedlings might affect the probability of equilibrium priority effects (alternative stable states) and transient priority effects (alternative transient states). 3. The model suggests that establishment-longevity tradeoff, in which annuals have competitive advantage over perennial seedlings, is a necessary condition for equilibrium priority effects. Equilibrium priority effects also require low fecundity in both annuals and perennials and small fitness differences, as determined by their relative fecundity, survival probability, and competitive ability at the seedling stage. 4. Transient priority effects need only small fitness differences. Furthermore, the model indicate that transient priority effects could last several decades under a range of the parameter space, exceeding the duration of typical experiments and observations. 5. Synthesis: Our results suggest that equilibrium priority effects driven by a life-history trade-off are possible but may be uncommon because they require unrealistically low fecundity . In contrast, transient priority effects should be more likely. Previous empirical findings of priority effects in grasslands may mostly indicate alternative transient , rather than stable , states, or other mechanisms than a life-history tradeoff .
Life-history tradeoffs among species are major drivers of community assembly. Most studies investigate how tradeoffs promote deterministic coexistence of species. It remains unclear how tradeoffs may instead promote historically contingent exclusion of species, where species dominance is affected by initial abundances, causing alternative community states. Focusing on the establishment-longevity tradeoff, we study the transient dynamics and equilibrium outcomes of competitive interactions in a simulation model of plant community assembly. We show that, in this model, the establishment-longevity tradeoff is a necessary but not sufficient condition for alternative stable equilibria that require also low fecundity for both species. An analytical approximation of our simulation model demonstrates that alternative stable equilibria are driven by demographic stochasticity in the number of seeds arriving at each establishment site. This site-scale stochasticity is only affected by fecundity and therefore occurs even in infinitely large communities. In many cases where the establishment-longevity tradeoff does not cause alternative stable equilibria, it still decreases the rate of convergence toward the single equilibrium, resulting in decades of transient dynamics that can appear indistinguishable from alternative stable equilibria in empirical studies .
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1. In many grassland communities, the identity of dominant speciesmay be determined by initial frequency owing to priority effects. Yet, the conditions for these priority effects remain unclear. 2. Focusing on interactions between annual and perennial plants, we used
Life-history tradeoffs among species are major drivers of community assembly. Most studies investigate how tradeoffs promote deterministic coexistence of species. It remains unclear how tradeoffs may instead promote historically contingent exclusion of species, where species dominance is affected by initial abundances, causing alternative community states. Focusing on the establishment-longevity tradeoff, we study the transient dynamics and equilibrium outcomes of competitive interactions in
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to investigate how longevity, fecundity, and the competitive ability of seedlings might affect the probability of equilibrium priority effects (alternative stable states) and transient priority effects (alternative transient states). 3. The model suggests that
of plant community assembly. We show that, in this model, the
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tradeoff, in which annuals have competitive advantage over perennial seedlings,
tradeoff
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condition for equilibrium priority effects. Equilibrium priority effects also require low
but not sufficient condition for alternative stable equilibria that require also low fecundity for both species. An analytical approximation of our simulation model demonstrates that alternative stable equilibria are driven by demographic stochasticity in the number of seeds arriving at each establishment site. This site-scale stochasticity is only affected by
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in both annuals and perennials and small fitness differences, as determined by their relative fecundity, survival probability, and competitive ability at the seedling stage. 4. Transient priority effects need only small fitness differences. Furthermore, the model indicate that transient priority effects could last several decades under a range of the parameter space, exceeding the duration of typical experiments and observations. 5. Synthesis: Our results suggest that equilibrium priority effects driven by a life-history trade-off are possible but may be uncommon because they require unrealistically low fecundity . In contrast, transient priority effects should be more likely. Previous empirical findings of priority effects in grasslands may mostly indicate alternative transient , rather than stable , states, or other mechanisms than a life-history tradeoff
and therefore occurs even in infinitely large communities. In many cases where the establishment-longevity tradeoff does not cause alternative stable equilibria, it still decreases the rate of convergence toward the single equilibrium, resulting in decades of transient dynamics that can appear indistinguishable from alternative stable equilibria in empirical studies