We hypothesize phyletic relationships among taxa of the didelphid mars
upial genus Philander, based on sequences of the mitochondrial cytochr
ome b gene. Data are available for six taxa recognized at either the s
pecific or subspecific levels, P. opossum opossum Linneaus (eastern an
d northeastern Amazonia), P. opossum canus Osgood (western Amazonia),
P. opossum fuscogriseus J. A. Alien (southeastern Central America), P.
opossum frenata Olfers (southeastern Brazil), P. andersoni andersoni
Osgood (northwestern Amazonia), and P. andersoni mcilhennyi Gardner an
d Patton (west-central Amazonia). Haplotype divergence is minimal to n
on-existent (<1% on average) between individuals within and among loca
lities for each taxon. The taxon inhabiting the Atlantic forest of coa
stal Brazil (P. o. frenata) is highly divergent from all others, avera
ging nearly 14% in sequence divergence. Maximal divergence among haplo
types representative of the other taxa examined is <8%. The combinatio
n of phylogenetic relationships and local sympatry suggests a greater
degree of species diversity for the genus than the two species P. opos
sum and P. andersoni. We recognize the Brazilian coastal P. frenata, a
s well as both P. andersoni and P. mcilhennyi, as valid species in add
ition to P. opossum. It is possible P. opossum is a composite, and tha
t further studies will accord species status to the Middle American, w
estern Amazonian, and eastern Amazonian-Guianan gray four-eyed opossum
s.