Angiosperms have become the dominant terrestrial plant group by diversifying for~145 million years into a broad range of environments. During the course of evolution, numerous morphological innovations arose, often preceded by whole genome duplications (WGD). The mustard family (Brassicaceae), a successful angiosperm clade with~4000 species, has been diversifying into many evolutionary lineages for more than 30 million years. Here we develop a species inventory, analyze morphological variation, and present a maternal, plastome-based genus-level phylogeny. We show that increased morphological disparity, despite an apparent absence of clade-specific morphological innovations, is found in tribes with WGDs or diversification rate shifts. Both are important processes in Brassicaceae, resulting in an overall high net diversification rate. Character states show frequent and independent gain and loss, and form varying combinations. Therefore, Brassicaceae pave the way to concepts of phylogenetic genome-wide association studies to analyze the evolution of morphological form and function.

Comparative mapping in cruciferous plants is ongoing, and recently two additional genetic maps of diploid Capsella and Arabidopsis lyrata subsp. petraea have been presented. We compared both maps with each other using the sequence map and genomic data resources from Arabidopsis thaliana as a reference. The ancestors of the species pair Capsella-Arabidopsis diverged from one another approximately 10-14 million years ago (mya), whereas Arabidopsis thaliana and Arabidopsis lyrata have been separated since roughly 5-6 mya. Our analysis indicated that among diploid Capsella and Arabidopsis lyrata all eight genetic linkage groups are totally colinear to each other, with only two inversions significantly differentiating these two species.By minimizing the number of chromosomal rearrangements during genome evolution, we presented a model of chromosome evolution involving all three species. From this scenario, it is obvious that Arabidopsis thaliana underwent a dramatic genome reconstruction, with a base chromosome number reduction from five to eight and with approximately 1.3 chromosomal rearrangements per million years. In contrast, the terminal lineage leading to Capsella has only undergone less than 0.09 rearrangements per million years. This is the same rate as calculated for Arabidopsis lyrata since its separation from the Capsella lineage 10-14 mya. These results are in strong contrast to all overestimated rates calculated from comparisons of the systems Arabidopsis thaliana and Brassica, and our data demonstrate the problematic nature of both model systems.

The Brassicaceae family (mustards or crucifers) includes Arabidopsis thaliana as one of the most important model species in plant biology and a number of important crop plants such as the various Brassica species (e.g. cabbage, canola and mustard). Moreover, the family comprises an increasing number of species that serve as study systems in many fields of plant science and evolutionary research. However, the systematics and taxonomy of the family are very complex and access to scientifically valuable and reliable information linked to species and genus names and its interpretation are often difficult. BrassiBase is a continuously developing and growing knowledge database (http://brassibase.cos.uni-heidelberg.de) that aims at providing direct access to many different types of information ranging from taxonomy and systematics to phylo- and cytogenetics. Providing critically revised key information, the database intends to optimize comparative evolutionary research in this family and supports the introduction of the Brassicaceae as the model family for evolutionary biology and plant sciences. Some features that should help to accomplish these goals within a comprehensive taxonomic framework have now been implemented in the new version 1.1.9. A 'Phylogenetic Placement Tool' should help to identify critical accessions and germplasm and provide a first visualization of phylogenetic relationships. The 'Cytogenetics Tool' provides in-depth information on genome sizes, chromosome numbers and polyploidy, and sets this information into a Brassicaceae-wide context.

Recently, we used the 5'-trnL(UAA)-trnF(GAA) region of the chloroplast DNA for phylogeographic reconstructions and phylogenetic analysis among the genera Arabidopsis, Boechera, Rorippa, Nasturtium, and Cardamine. Despite the fact that extensive gene duplications are rare among the chloroplast genome of higher plants, within these taxa the anticodon domain of the trnF(GAA) gene exhibit extensive gene duplications with one to eight tandemly repeated copies in close 5' proximity of the functional gene. Interestingly, even in Arabidopsis thaliana we found six putative pseudogenic copies of the functional trnF gene within the 5'-intergenic trnL-trnF spacer. A reexamination of trnL(UAA)-trnF(GAA) regions from numerous published phylogenetic studies among halimolobine, cardaminoid, and other cruciferous taxa revealed not only extensive trnF gene duplications but also favor the hypothesis about a single origin of trnF pseudogene formation during evolution of the Brassicaceae family 16-21 MYA. Conserved sequence motifs from this tandemly repeated region are codistributed nonrandomly throughout the plastome, and we found some similarities with a DNA sequence duplication in the rps7 gene and its adjacent spacer. Our results demonstrate the potential evolutionary dynamics of a plastidic region generally regarded as highly conserved and probably cotranscribed and, as shown here for several genera among cruciferous plants, greatly characterized by parallel gains and losses of duplicated trnF copies.

Different concentrations of 14 C radiolabeled cultures of the prymnesiophyte Isochrysis galbana (5.5 m in size), the prasinophyte Tetraselmis suecica (9.5 m), and the chlorophyte Chlorella sp. (3.5 m) were offered as food to groups of 2-5 Oikopleura dioica to determine the response of clearance (CR) and ingestion (IR) rates to food concentration (FC for the prey I. galbana, T. suecica, and Chlorella sp., respectively. The K m values are high and in two of three cases exceed the maximum concentration of ingestible particles found in the natural habitat, which suggests that O. dioica is adapted to high phytoplankton concentrations. In contrast with classical FR models, CR remained nearly constant for all concentrations. Particles cleared from suspension by O. dioica are ingested and transformed into fast-sinking fecal pellets at low FC, while they are mainly accumulated into slow to fast-sinking filter houses at high FC, which implies considerable shifts in the biogeochemical role of these animals with changing particle concentrations.