  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.
