Comparative analyses of the sequence of entire genomes have shown that gene duplications, chromosomal segmental duplications, or even whole genome duplications (WGD) have played prominent roles in the evolution of many eukaryotic species.Here, we used the ancient duplication of a well known transcription factor in maize, encoded by the locus is contained within a 1.25 million base-pair (Mb) segment on chromosome 7, which was duplicated ≈56 million years ago (mya) before the split of rice and maize 50 mya.However, this approach can be difficult to interpret and is not always reliable (see Blanc and Wolfe, 2004; Patterson et al., 2004).
There are still several issues with the gene tree species tree mapping approach. These include ancient whole genome duplication (WGD) events in basal angiosperm lineages, as well as a proposed paleohexaploid event that may have occurred close to the eudicot divergence (Fig. The question is no longer “what proportion of angiosperms are polyploid? ” but “how many episodes of polyploidy characterize any given lineage? Polyploidy has long been recognized as a major force in angiosperm evolution. Recent genomic investigations employing sequenced genomes and large EST collections not only indicate that polyploidy is ubiquitous among angiosperms, but also suggest several ancient genome-doubling events.