Pollen performance of Raphanus sativus (Brassicaceae) declines in response to elevated [CO(2)].

Although increases in atmospheric [CO(2)] are known to affect plant physiology, growth and reproduction, understanding of these effects is limited because most studies of reproductive consequences focus solely on female function. Therefore, we examined the effects of CO(2) enrichment on male function in the annual Raphanus sativus. Pollen donors grown under elevated [CO(2)] initially sired a higher proportion of seeds per fruit than ambient [CO(2)]-grown plants when each was tested against two different standard competitors; however, by the end of the 5-month experiment, these pollen donors sired fewer seeds than ambient [CO(2)]-grown plants and produced a lower proportion of viable pollen grains. The results of this experiment confirm that elevated [CO(2)] can alter reproductive success. Additionally, the change in response to elevated [CO(2)] over time varied among pollen donor families; thus, changes in [CO(2)] could act as a selective force on this species.

Phylogeny of the Callandrena subgenus of Andrena (Hymenoptera: Andrenidae) based on mitochondrial and nuclear DNA data: polyphyly and convergent evolution.

We propose a phylogenetic hypothesis of relationships within Callandrena, a North American subgenus of the bee genus Andrena, based on both mitochondrial and nuclear DNA sequences. Our data included 695 aligned base pairs comprising parts of the mitochondrial genes cytochrome oxidase subunits I and II and the intervening tRNA-leucine and 767 aligned base pairs of the F2 copy of the nuclear gene elongation factor-1alpha. We also suggest a preliminary hypothesis of relationships of the North American subgenera in the genus. Our analyses included 54 species of Callandrena, 42 species of Andrena representing 24 additional subgenera, and 11 outgroup species in the family Andrenidae. Parsimony analyses of each marker separately suggested that Callandrena was polyphyletic, with a combined analysis suggesting that there were at least two phylogenetically independent clades of bees with similar morphological features. Maximum likelihood and Bayesian analyses supported this conclusion, as did the non-parametric bootstrapping SOWH test. Convergence in morphological characters was likely due to their common use of members of Asteraceae as pollen hosts.