Phylogeny, ecology, and the coupling of comparative and experimental approaches. Trends in ecology & evolution 27

Recent progress in the development of phylogenetic methods and access to molecular phylogenies has made comparative biology more popular than ever before. However, determining cause and effect in phylogenetic comparative studies is inherently difficult without experimentation and evolutionary replication. Here, we provide a roadmap for linking comparative phylogenetic patterns with ecological experiments to test causal hypotheses across ecological and evolutionary scales. As examples, we consider five cornerstones of ecological and evolutionary research: tests of adaptation, tradeoffs and synergisms among traits, coevolution due to species interactions, trait influences on lineage diversification, and community assembly and composition. Although several scenarios can result in a lack of concordance between historical patterns and contemporary experiments, we argue that the coupling of phylogenetic and experimental methods is an increasingly revealing approach to hypothesis testing in evolutionary ecology. Why integrate phylogenies and experiments? The joint application of comparative phylogenetic and experimental methods has been advocated since at least the 1990s as a way to generate and evaluate causal hypotheses in evolutionary ecology We begin with a general conceptual framework for integrating manipulative experiments with comparative phylogenetics. However, because the methods, benefits and challenges associated with coupling these approaches change with the hypothesis being addressed, we consider five major areas in evolutionary ecology: tests of adaptation, trait tradeoffs and synergisms, coevolution and cospeciation, trait influences on lineage diversification, and ecological community structure. A conceptual roadmap for integrative, reciprocal hypothesis testing When used in isolation, phylogenetic and experimental approaches can each generate hypotheses that are then testable using the alternative approach Despite the benefits of integrating approaches, the reconciliation of results from contemporary and historical studies can present logistical and interpretational challenges. For example, the comparison of experimental results across multiple species within a clade often involves a common garden design, which can lead to variable results simply because species are removed from the ecological context in which they evolved. Furthermore, interpretational issues arise when experimental and comparative results conflict Review Corresponding author: Weber, M.G. (mgw58@cornell.edu)