Functional trait space and the latitudinal diversity gradient.

The processes causing the latitudinal gradient in species richness remain elusive. Ecological theories for the origin of biodiversity gradients, such as competitive exclusion, neutral dynamics, and environmental filtering, make predictions for how functional diversity should vary at the alpha (within local assemblages), beta (among assemblages), and gamma (regional pool) scales. We test these predictions by quantifying hypervolumes constructed from functional traits representing major axes of plant strategy variation (specific leaf area, plant height, and seed mass) in tree assemblages spanning the temperate and tropical New World. Alpha-scale trait volume decreases with absolute latitude and is often lower than sampling expectation, consistent with environmental filtering theory. Beta-scale overlap decays with geographic distance fastest in the temperate zone, again consistent with environmental filtering theory. In contrast, gamma-scale trait space shows a hump-shaped relationship with absolute latitude, consistent with no theory. Furthermore, the overall temperate trait hypervolume was larger than the overall tropical hypervolume, indicating that the temperate zone permits a wider range of trait combinations or that niche packing is stronger in the tropical zone. Although there are limitations in the data, our analyses suggest that multiple processes have shaped trait diversity in trees, reflecting no consistent support for any one theory.

Habitat area and climate stability determine geographical variation in plant species range sizes.

Despite being a fundamental aspect of biodiversity, little is known about what controls species range sizes. This is especially the case for hyperdiverse organisms such as plants. We use the largest botanical data set assembled to date to quantify geographical variation in range size for ~ 85 000 plant species across the New World. We assess prominent hypothesised range-size controls, finding that plant range sizes are codetermined by habitat area and long- and short-term climate stability. Strong short- and long-term climate instability in large parts of North America, including past glaciations, are associated with broad-ranged species. In contrast, small habitat areas and a stable climate characterise areas with high concentrations of small-ranged species in the Andes, Central America and the Brazilian Atlantic Rainforest region. The joint roles of area and climate stability strengthen concerns over the potential effects of future climate change and habitat loss on biodiversity.

Tetrahymena Genome Database Wiki: a community-maintained model organism database.

When funding for Tetrahymena Genome Database (TGD) ended in 2006, no further updates were made to this important community resource and the main database was taken offline in 2008. We have restored and updated this important resource for use by the Tetrahymena research community. We have also retooled the TGD website (now TGD Wiki) to allow members of the community to directly update the information presented for each gene, including gene names, descriptions and Gene Ontology annotations, from a web browser. Maintenance of genome annotations by the authors generating and publishing primary data, rather than dedicated scientific curators, is a viable alternative for the upkeep of genomes, particularly for organisms with smaller research communities. By combining simple, intuitive displays with the powerful search functions made possible by its underlying relational database, TGD Wiki has been designed to maximize participation by bench scientists in the development of their community bioinformatics resource. DATABASE URL: http://ciliate.org.