Before beginning to reconstruct the species' evolutionary history, the team had to decide which model of evolution would inform their project. "There are a number of models out there that talk about how evolution occurs. They represent the different general principles that evolution might have followed," says David A. Bader, an electrical and computer engineering professor at the University of New Mexico.

Some models figure the likelihood of given events within the species' history, such as duplications, deletions, and insertions of genes, and use that information to create possible histories. These methods are computationally expensive, and gathering the data necessary to run them is difficult.

Rather than taking a statistical approach, however, the model used by Bader and Moret's team was built on an idea known as parsimony. "By saying parsimony, we're basically saying that nature is efficient," says Moret. "It gives rise to new species through the least amount of change. Parsimony is founded on the same principle as Occam's razor: the simplest explanation is the best. Here, the shortest evolutionary path is the best."

The team arrived at this theory by following the lead of biologists like their colleague Robert Jansen, chairman of the University of Texas at Austin's Section of Integrative Biology, who studies evolution and collects the gene data used by the team. The gene data are taken from the chloroplast of each species of Campanulaceae. Chloroplasts provide energy for the plant cells and do not occur independently outside of cells. They also make excellent candidates for phylogenic reconstruction because each chloroplast has a single chromosome. The genes on the chloroplasts' chromosomes have been sequenced, and biologists like Jansen hypothesize that evolution occurs through a mechanism known as inversion. Inversion contributes to evolution by changing the order and orientation of a sequence of genes within a genome. At times inversions may even undo themselves, returning the order of genes on the chloroplast chromosome to its former state.