Convergent evolution of a complex fruit structure in the tribe Brassiceae (Brassicaceae).

Premise Of Study: Many angiosperms have fruit morphologies that result in seeds from the same plant having different dispersal capabilities. A prime example is found in the Brassiceae (Brassicaceae), which has many members with segmented or heteroarthrocarpic fruits. Since only 40% of the genera are heteroarthrocarpic, this tribe provides an opportunity to study the evolution of an ecologically significant novelty and its variants.

Natural variation in germination responses of Arabidopsis to seasonal cues and their associated physiological mechanisms.

Background And Aims: Despite the intense interest in phenological adaptation to environmental change, the fundamental character of natural variation in germination is almost entirely unknown. Specifically, it is not known whether different genotypes within a species are germination specialists to particular conditions, nor is it known what physiological mechanisms of germination regulation vary in natural populations and how they are associated with responses to particular environmental factors.

Methods: We used a set of recombinant inbred genotypes of Arabidopsis thaliana, in which linkage disequilibrium has been disrupted over seven generations, to test for genetic variation and covariation in germination responses to distinct environmental factors.