Learning from dynamic traits: Seasonal shifts yield insights into ecophysiological tradeoffs across scales from macroevolutionary to intra-individual
Mason, Chase et al. (2019), Learning from dynamic traits: Seasonal shifts yield insights into ecophysiological tradeoffs across scales from macroevolutionary to intra-individual, Dryad, Dataset, https://doi.org/10.5061/dryad.wh70rxwhr
Premise of the Research. Phylogenetic comparative methods provide a powerful approach for exploring the macroevolution of plant functional traits. Such approaches can uncover trait-trait correlations through evolutionary time, as well as provide evidence of the role of traits in adaptation across environmental gradients. For continuous traits, most phylogenetic comparative approaches to date employ a single trait value per species, often a mean of sampled individuals, or alternatively incorporate intraspecific variation as a distribution around such a mean. It has been known for quite some time that many of the most physiologically and ecologically important plant traits are actually highly plastic, changing dynamically across a growing season, with whole-plant development, or in response to environmental conditions. Here we demonstrate one possible approach to assessing the evolution of such dynamic traits, the use of function-valued phylogenetic comparative methods.
Methodology. Leaf traits were sampled across 25 taxa in the genus Cornus at six time points throughout the growing season in a common garden context, followed by contrasting sets of alternative analyses to demonstrate the consequences of researcher decisions on study conclusions.
Pivotal Results. The vast majority of assessed traits exhibit substantial seasonal shifts. These shifts cause traditional macroevolutionary correlations assessed at different sampling dates to yield conflicting results. Function-valued approaches indicate that seasonal shifts in many traits are evolutionarily correlated, with implications for the origin of trait-trait tradeoffs. Seasonal trait plasticity is also evolutionarily correlated with native habitat environmental gradients across Cornus.
Conclusions. Because a very large number of plant functional traits are not fixed, but vary dynamically over time or with environmental conditions, stronger insights into the evolution of plant functional traits can emerge when this dynamism is explicitly incorporated into phylogenetic comparative approaches. We encourage the adoption of such approaches, as well as the development of better tools for doing so.
Leaf trait data sampled from the collections of the Arnold Arboretum over the 2015 growing season. Missing data is indicated by a period. See article full text for details. Native habitat climate and soil data derived from global climate and soil data layers using occurrence data from digitized herbarium records housed on GBIF and iDigBio. See article full text for details. Results of phylogenetic comparative analyses also included, analyzed as described in the article full text.
The unique plant identification numbers used in the data presented here refer to the Arnold Arboretum plant accession naming system, and can be cross-referenced with ArbExplorer and other public resources about the collections.
Arnold Arboretum, Award: Katharine H. Putnam Fellowship in Plant Science