Phylogeny and growth strategy as predictors of differences in cobalt concentrations between plant species

Analyses reported here quantify the contribution of plant phylogeny and plant growth strategy to soil-to-plant transfer of Co. Estimated relative mean (ERM) Co concentrations in shoots of 241 species of flowering plant were derived using a residual maximum likelihood (REML) analysis. There were significant differences in, and a loge-normal frequency distribution of, ERM Co concentrations between species. A significant percentage of interspecies variance could be assigned to taxonomic categories above the species, (Family and above 21.5%; Order and above 12.22%). Time-series analysis of ERM Co concentrations ordered in the species-sequence of the Angiosperm Phylogeny Group (APG II (2003)) revealed significant autocorrelation with an increase from Commelinid Monocot to Asterid Eudicot and a pronounced peak in the Core Eudicots. ERM Co concentrations categorized by plant growth strategy sensu Grime (2001) showed an increase toward stress-tolerant strategies. Plant species are not, therefore, independent units of Co concentration--factors derived from higher levels of biological organization exert significant effects. These effects can provide the basis of new techniques for selecting plant species for biotechnologies and for predicting the exposure of organisms to Co. They show that plant phylogeny and growth strategy might help refine predictions of soil-to-plant transfer of a variety of pollutants, and suggest research that might link molecular and higher level processes in contaminated soil-plant systems.