Domains of Life: Plants
Hybridization and polyploidy have played a key role in plant speciation, complicating the reconstruction of their phylogenetic histories (Bergthorsson et al. 2003). However, the impact of these processes on species identification will be small unless they have led to many cases of recent (<100K years) speciation or to the regular genesis of F1 hybrids. As this does not seem to be the case, DNA-based approaches to species identification should be effective.
Projects such as Deep Green have provided a comprehensive understanding of the patterning of genetic diversity in the plant kingdom (Barkman et al. 2000), information useful in designing a DNA barcoding system for plants. For example, past work has revealed that rates of mitochondrial evolution are far slower in plants than animals, making COI an unlikely candidate. Fortunately, rates of evolution in the chloroplast genome are higher (Wolfe et al. 1987). Much past work has focused on the analysis of sequence diversity in rbcL and this gene is able to deliver generic-level identifications (Mark Chase, pers. comm.). Other chloroplast genes, such as mat-K, show promise in generating species identifications.
References
- Barkman, T. J. et al. 2000. Independent and combined analyses of sequences from all three genomic compartments converge on the root of flowering plant phylogeny. Proc. Natl. Acad. Sci USA 97: 13166-13171.
- Bergthorsson, U., K. L. Adams, B. Thomason and J. D. Palmer. 2003. Widespread horizontal transfer of mitochondrial genes in flowering plants. Nature 424:197-201.
- Wolfe, K. H., W. S. Li and P. M. Sharpe. 1987. Rates of nucleotide substitution vary greatly among plant mitochondrial, chloroplast, and nuclear DNAs. Proc. Natl. Acad. Sci USA 84:9054-9058.