These
rodents are clearly most closely related to some
muroid rodents found on the
African mainland. Some
molecular phylogeneticists consider this clade of Malagasy and African rodents to represent a distinct family, the
Nesomyidae. Other researchers place the Nesomyinae into a large family,
Muridae, along with all members of the superfamily
Muroidea.
It has been reported that the Nesomyinae is not
monophyletic,[2] but this has not been supported in other analyses. Additionally, there were problems with this particular study, notably the use of Calomyscus as an
outgroup while more distantly related
muroids (
rhyzomyines) were included in the
ingroup. It seems likely that all
rodents in
Madagascar are descendants from a single invasion of the island.
If monophyletic, the nesomyines represent one of only four colonization events of terrestrial mammals from mainland Africa. The other groups are
tenrecs,
lemurs and
Malagasy carnivorans.
Molecular clock analyses suggest that the ancestor of the nesomyines colonized Madagascar about 20-25 million years ago.[3] This is at approximately the same time as the Malagasy carnivorans, but is considerably more recent than the estimated colonization times of tenrecs and lemurs.
^Jansa, S.A.; Weksler, M. (2004). "Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences". Molecular Phylogenetics and Evolution. 31 (1): 256–276.
doi:
10.1016/j.ympev.2003.07.002.
PMID15019624.
Steppan, S. J.; Adkins, R. A.; Anderson, J. (2004). "Phylogeny and divergence date estimates of rapid radiations in muroid rodents based on multiple nuclear genes". Systematic Biology. 53 (4): 533–553.
doi:
10.1080/10635150490468701.
PMID15371245.