Picante: R tools for integrating phylogenies and ecology.

SUMMARY: Picante is a software package that provides a comprehensive set of tools for analyzing the phylogenetic and trait diversity of ecological communities. The package calculates phylogenetic diversity metrics, performs trait comparative analyses, manipulates phenotypic and phylogenetic data, and performs tests for phylogenetic signal in trait distributions, community structure and species interactions. AVAILABILITY: Picante is a package for the R statistical language and environment written in R and C, released under a GPL v2 open-source license, and freely available on the web (http://picante.r-forge.r-project.org) and from CRAN (http://cran.r-project.org).

The major veins of mesomorphic leaves revisited: tests for conductive overload in Acer saccharum (Aceraceae) and Quercus rubra (Fagaceae).

Many leaves survive the severing of their major veins in apparently excellent health. According to the classical explanation, the leaf minor veins provide "conductive overload," an excess of parallel conductive paths, rendering the major veins hydraulically dispensable. Whether such an excess of conductive paths exists has important implications for vascular design and for leaf response to vascular damage. We subjected leaves of Acer saccharum and Quercus rubra to cutting treatments that disrupted the major vein system and determined leaf survival, stomatal conductance (g), quantum yield of photosystem II (Φ(PSII)), and leaf hydraulic conductance (K(leaf)). For A. saccharum, the cuts led to the death of distal lamina. For Q. rubra, however, the treated leaves typically remained apparently healthy. Despite their appearance, the treated Q. rubra leaves had a strongly reduced K(leaf), relative to control leaves, and g and Φ(PSII) were reduced distal to the cuts, respectively, by 75-97% and 48-76%. Gas exchange proximal to the cuts was unaffected, indicating the independence of lamina regions and their local stomata. Analogous results were obtained with excised Q. rubra leaves. These studies demonstrate an indispensable, vital role of the major veins in conducting water throughout the lamina.