Evolutionary relationships among HIV-2 and SIVsmm Nef sequences. SIVsmm nef alleles newly analyzed in the present study and the SIVmac239 nef are highlighted by yellow and orange boxes, respectively. The tree in was inferred by the Bayesian method  MrBayes  using 10 million generations and the HKY model  with gamma distributed rates at sites  and burn in of 25%. Numbers on branches are percentage estimated posterior probabilities. Only those 95% and above are shown.