Measuring the Evolutionary Distances between Brassicaceae Species

Abstract

Evolutionary relationships can help us understand the history and evolution of a species. Evolutionary relationships are often discovered or confirmed by molecular phylogeny, which allows us to compare species by their genomes. About 9-15 million years ago, the Brassica genus, which includes canola, broccoli, mustards, and other plants, experienced a whole genome triplication event. This event not only increased the size of the genome, but also the number of duplicated genes within it. We used the Genome REarrangements with Duplications (GREDU) software package to find the double-cut-and-join edit distances between five Brassicaceae species, three of which were from the Brassica genus. GREDU rearranges genomes to find an approximation of the smallest number of rearrangements that must be made to transform one genome into the other. The smaller the number, the closer any two species are predicted to be. GREDU notably supports the comparison of genomes with duplicate genes included in the calculation, which is important when working with Brassica species. We were able to reconstruct the widely accepted phylogenetic tree of the species studied, however we discovered that the GREDU tool may not be best when comparing Brassica species due to the high number of duplicate genes. Future areas of research include determining the actual edit distances between species and analyzing whether GREDU is an appropriate package for conducting comparisons when species have a high number of duplicated genes.