SYSTEMATICS OF MAXOMYS SODY, 1936 (RODENTIA, MURIDAE, MURINAE) - DNA DNA HYBRIDIZATION STUDIES OF SOME BORNEO-JAVAN SPECIES AND ALLIED SUNDAIC AND AUSTRALO-PAPUAN GENERA/

We compared five species of the murine genus Maxomys and representativ es of nine other murid genera in a complete 15 x 15 DNA-hybridization matrix. FITCH trees were calculated for the entire suite of taxa and f or subsets including only the five Maxomys and these together with the four nearest outgroups. All trees were validated by 'bootstrapping' a nd by jackknifing, performing bath single- and multiple-deletions of t axa. The full 15 x 15 data set indicated a sister-group relationship b etween Maxomys and two pairs of genera (Sundamps-Rattus sensu stricto and Niviventer-Leopoldamys) that are more closely related to each othe r than to Maxomys; addition of data on Bandicota and Berylmys from ano ther recent DNA-hybridization study confirmed that these genera are su ccessive sister-taxa to the Sundamys-Rattus pair. Mus-Myomys and Uromy s-Melomys were each distinct lineages from the above grouping of Rattu s sensu late species, and from the putative outgroup sigmodontine Pero myscus, but the interrelations of the three murine clades were unresol ved. Within Maxomys, M. surifer and M. bartelsii are a related pair, a nd M. ochraceiventer probably forms an unresolved trio with M. rajah a nd M. whiteheadi. Calibration of a tree generated from saturation-corr ected distances against a likely divergence-date of 12.2 Mybp for the separation of Mus and Rattus confirms a high rate of single-copy DNA c hange in murids (2.1%/Myr); and suggests that Sigmodontinae and Murina e diverged at around 15.3 Mybp, that Maxomys and the group of six othe r Ratius sensu lato separated approximately 7.6 Myr ago, and that Maxo mys began to diversify 4.8 Myr ago. (C) 1997 The Linnean Society of Lo ndon.