A phylogenetic network is any graph used to visualize evolutionary relationships (either abstractly or explicitly)[1] between nucleotide sequences, genes, chromosomes, genomes, or species.
Phylogenetic networks can be inferred and visualised with software such as SplitsTree,[4] the R-package, phangorn,[5][6] and, more recently, Dendroscope.
Phylogenetic trees also have trouble depicting microevolutionary events, for example the geographical distribution of muskrat or fish populations of a given species among river networks, because there is no species boundary to prevent gene flow between populations.
In most cases, such networks only depict relations between taxa, without giving information about the evolutionary history.
Although computational simplicity is the main goal, most of these classes have a biological justification as well.