Empirical Approaches to Infer Fitness from Traits

Abstract

Abstract The fitness of a single species varies along environmental gradients. The fitness of multiple species along environmental gradients can be modeled as a non-linear interaction between their traits and the environment. Changes in demographic rates will determine whether species ranges shift in response to climate change. Observational approaches to modeling fitness can leverage long-term monitoring datasets and population models. Intrinsic and invasion growth rates can be computed after accounting for conspecific and heterospecific neighborhood densities, although these methods differ from those in modern coexistence theory. Observations of failed introductions into unsuitable habitats are just as important as observations of stable and growing populations. Observational demographic datasets often lack measurements of population declines outside their natural range of environmental conditions precisely because the species cannot live in those conditions. Experiments are useful to identify the environments in which populations decline by forcing the filtering process to occur, although large observational datasets may have enough variation in them to still be useful. Common gardens beyond species ranges are the gold standard because they provide experimental control over environmental conditions and competitive interactions. Integrative measures of fitness are superior to single demographic rates at detecting reductions in performance beyond species ranges.