DEFINITION OF SPECIES OF POUCHED 4-EYED OPOSSUMS (DIDELPHIDAE, PHILANDER)

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.