Figure 3
From: GIGA: a simple, efficient algorithm for gene tree inference in the genomic age
GIGA rules for duplication events. GIGA infers that a duplication must have occurred using Rule 2, as the two OS's being joined contain two genes from both Baker's yeast (YEAST) and fission yeast (SCHPO). It then places the duplication just prior to the most recent MRCA speciation event (fungi, in this case), which is the most parsimonious solution with respect to gene deletion events (Rule 3). Note that many other solutions are possible (two examples are shown below the most parsimonious case), but they require an increasing number of independent gene deletion events.