Molecular phylogeny and biogeography of the native rodents of Madagascar (Muridae : Nesomyinae): A test of the single-origin hypothesis

Complete nucleotide sequences from the mitochondrial cytochrome b gene (114 3 bp) were used to investigate the phylogenetic relationships among the nat ive rodents of Madagascar. Specifically, this study examines whether the ni ne genera of nesomyines form a monophyletic group relative to other Old Wor ld murids. All nine of the nesomyine genera, including multiple individuals from 15 of the 21 described species, were included in the analysis, and th eir monophyly was assessed relative to the murid subfamilies Mystromyinae, Petromyscinae, Dendromurinae, Cricetomyinae, Murinae, Rhizomyinae, and Calo myscinae. Phylogenetic analysis of the resulting 95 taxa and 540 characters resulted in 502 equally parsimonious cladograms. The strict consensus tree weakly refutes the monophyly of Nesomyinae and suggests that the Malagasy rodents form a clade with dendromurines (as represented by Steatomys) and t he African rhizomyine Tachyoryctes. The cladogram strongly refutes the asso ciation of the South African genus Mystromys with the Malagasy genera and s uggests that Petromyscus and Mystromys form a monophyletic group. We provid e the first explicitly phylogenetic scenario for the biogeographic history of nesomyine rodents. Our phylogenetic hypothesis indicates: (1) rodents in vaded Madagascar only once, (2) they came from Asia not from Africa as is c ommonly assumed, and (3) there was a secondary invasion of rodents from Mad agascar into Africa. (C) 1999 The Willi Hennig society.