Allozyme genetic distances and evolutionary relationships in marsupials of North and South America

AUozyme genetic distances and variability were studied by horizontal starch gel electrophoresis in 6 species of marsupials from North and South America representing 4 different genera. Twenty-one presumptive loci were assessed in a total of 151 specimens. Only 1 of 21 loci was found to be monomorphic in the whole sample. Phenetic and cladistic interspecific analysis coincided in rendering two sharply dif­ferentiated subgroups: one comprising species of the genus Didelphis Linnaeus, 1758 CD. marsupialis Linnaeus, 1758, D. virginiana Kerr, 1792 and D. albiventris Lund, 1840), and the other comprising Monodelphis dimidiata fWagner, 1847}, Lestodelphys halli (Thomas, 1921) and Lutreolina crassicaudata (Desmarest, 1804). No relationships between the bradytelic condition, the karyotype stability of this group, and genetic variability were found. On the other hand, the existence of species with brief life span such as Lestodelphys halli and Monodelphis dimidiata (Marmosini tribe) and species with long life span (Didelphini tribe) allowed us to test the hypothesis which correlates generation-time with genetic variability. We conclude that a general explanation for genetic variability must involve more than just generation-time,