Jeannine Cavender-Bares

The worldwide leaf economics spectrum

Bringing together leaf trait data spanning 2,548 species and 175 sites we describe, for the first time at global scale, a universal spectrum of leaf economics consisting of key chemical, structural and physiological properties. The spectrum runs from quick to slow return on investments of nutrients and dry mass in leaves, and operates largely independently of growth form, plant functional type or biome. Categories along the spectrum would, in general, describe leaf economic variation at the global scale better than plant functional types, because functional types overlap substantially in their leaf traits. Overall, modulation of leaf traits and trait relationships by climate is surprisingly modest, although some striking and significant patterns can be seen. Reliable quantification of the leaf economics spectrum and its interaction with climate will prove valuable for modelling nutrient fluxes and vegetation boundaries under changing land-use and climate.

The merging of community ecology and phylogenetic biology

The increasing availability of phylogenetic data, computing power and informatics tools has facilitated a rapid expansion of studies that apply phylogenetic data and methods to community ecology. Several key areas are reviewed in which phylogenetic information helps to resolve long-standing controversies in community ecology, challenges previous assumptions, and opens new areas of investigation. In particular, studies in phylogenetic community ecology have helped to reveal the multitude of processes driving community assembly and have demonstrated the importance of evolution in the assembly process. Phylogenetic approaches have also increased understanding of the consequences of community interactions for speciation, adaptation and extinction. Finally, phylogenetic community structure and composition holds promise for predicting ecosystem processes and impacts of global change. Major challenges to advancing these areas remain. In particular, determining the extent to which ecologically relevant traits are phylogenetically conserved or convergent, and over what temporal scale, is critical to understanding the causes of community phylogenetic structure and its evolutionary and ecosystem consequences. Harnessing phylogenetic information to understand and forecast changes in diversity and dynamics of communities is a critical step in managing and restoring the Earths biota in a time of rapid global change.

The Evolution of Plant Functional Variation: Traits, Spectra, and Strategies

Variation in plant functional traits results from evolutionary and environmental drivers that operate at a variety of different scales, which makes it a challenge to differentiate among them. In this article we describe patterns of functional trait variation and trait correlations within and among habitats in relation to several environmental and trade‐off axes. We then ask whether such patterns reflect natural selection and can be considered plant strategies. In so doing we highlight evidence that demonstrates that (1) patterns of trait variation across resource and environmental gradients (light, water, nutrients, and temperature) probably reflect adaptation, (2) plant trait variation typically involves multiple‐correlated traits that arise because of inevitable trade‐offs among traits and across levels of whole‐plant integration and that must be understood from a whole‐plant perspective, and (3) such adaptation may be globally generalizable for like conditions; i.e., the set of traits (collections of traits in syndromes) of taxa can be considered as “plant strategies.”

Phylogenetic Overdispersion in Floridian Oak Communities

Closely related species that occur together in communities and experience similar environmental conditions are likely to share phenotypic traits because of the process of environmental filtering. At the same time, species that are too similar are unlikely to co‐occur because of competitive exclusion. In an effort to explain the coexistence of 17 oak species within forest communities in North Central Florida, we examined correlations between the phylogenetic relatedness of oak species, their degree of co‐occurrence within communities and niche overlap across environmental gradients, and their similarity in ecophysiological and life‐history traits. We show that the oaks are phylogenetically overdispersed because co‐occurring species are more distantly related than expected by chance, and oaks within the same clade show less niche overlap than expected. Hence, communities are more likely to include members of both the red oak and the \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape

Phylogenetic structure of floridian plant communities depends on taxonomic and spatial scale

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\end{document} oak clades than only members of one clade. This pattern of phylogenetic overdispersion arises because traits important for habitat specialization show evolutionary convergence. We hypothesize further that certain conserved traits permit coexistence of distantly related congeners. These results provide an explanation for how oak diversity is maintained at the community level in North Central Florida.

A Framework Phylogeny of the American Oak Clade Based on Sequenced RAD Data

Background Two decades of research showing that increasing plant diversity results in greater community productivity has been predicated on greater functional diversity allowing access to more of the total available resources. Thus, understanding phenotypic attributes that allow species to partition resources is fundamentally important to explaining diversity-productivity relationships. Methodology/Principal Findings Here we use data from a long-term experiment (Cedar Creek, MN) and compare the extent to which productivity is explained by seven types of community metrics of functional variation: 1) species richness, 2) variation in 10 individual traits, 3) functional group richness, 4) a distance-based measure of functional diversity, 5) a hierarchical multivariate clustering method, 6) a nonmetric multidimensional scaling approach, and 7) a phylogenetic diversity measure, summing phylogenetic branch lengths connecting community members together and may be a surrogate for ecological differences. Although most of these diversity measures provided significant explanations of variation in productivity, the presence of a nitrogen fixer and phylogenetic diversity were the two best explanatory variables. Further, a statistical model that included the presence of a nitrogen fixer, seed weight and phylogenetic diversity was a better explanation of community productivity than other models. Conclusions Evolutionary relationships among species appear to explain patterns of grassland productivity. Further, these results reveal that functional differences among species involve a complex suite of traits and that perhaps phylogenetic relationships provide a better measure of the diversity among species that contributes to productivity than individual or small groups of traits.

Monitoring plant functional diversity from space

Consideration of the scale at which communities are defined both taxonomically and spatially can reconcile apparently contradictory results on the extent to which plants show phylogenetic niche conservatism. In plant communities in north central Florida, we collected species abundances in 55 0.1-ha plots in several state parks. When communities were defined narrowly to include a single phylogenetic lineage, such as Quercus, Pinus, or Ilex, neighbors tended to be less related than expected (phylogenetic overdispersion) or there was no pattern. If the same communities were defined more broadly, such as when all seed plants were included, neighbors tended to be more related than expected (phylogenetic clustering). These results provide evidence that species interactions among close relatives influence community structure, but they also show that niche conservatism is increasingly evident as communities are defined to include greater phylogenetic diversity. We also found that, as the spatial scale is increased to encompass greater environmental heterogeneity, niche conservatism emerges as the dominant pattern. We then examined patterns of trait evolution in relation to trait similarity within communities for 11 functional traits for a single phylogenetic lineage (Quercus) and for all woody plants. Among the oaks, convergent evolution of traits important for environmental filtering contributes to the observed pattern of phylogenetic overdispersion. At the broader taxonomic scale, traits tend to be conserved, giving rise to phylogenetic clustering. The shift from overdispersion to clustering can be explained by the increasing conservatism of traits at broader phylogenetic scales.