Data from: Luck or pluck: does trait variation or chance drive variation in lifetime reproductive success?

While there has been extensive interest in how intraspecific trait variation affects ecological processes,
outcomes are highly variable even when individuals are identical: some are
lucky while others are not. Trait variation is therefore only important if it adds substantially to the
variability produced by luck. We ask when trait variation has a substantial effect on variability in
lifetime reproductive success (LRS), using two approaches: 1) we partition the variation in LRS into
contributions from luck and trait variation; 2) we ask what can be inferred about an individual's
traits, and with what certainty, given their observed LRS. In theoretical stage- and size-structured models,
and two empirical case studies, we find that luck usually dominates the variance of LRS. Even when individuals
differ substantially in ways that affect expected LRS, unless the effects of luck are substantially
reduced (e.g. low variability in reproductive lifespan or in annual fecundity), most variance in
lifetime outcomes is due to luck, implying that departures from "null" models omitting trait
variation will be hard to detect. Luck also obscures the relationship between realized LRS
and individual traits. While trait variation may influence the fate of populations, luck
often governs the lives of individuals.