which is the oldest

[arctos]

Dear All
I sequenced trnL-F (cpDNA) of 13 populations of a plant species (from a monotypic family). They are different from each other, even with big gaps (about 100 bp). My question is, just based on the sequences without any from outgroup species, how could I find the oldest, from a evolutionary perspective. I wish to find the migeration route of this plant using these sequences. Or which software is the best to do this work? I tried some softwares used in phyogenetics such as phylip, mega and etal. I am confused because I don't know which is aproperate.
Sorry for my English, Thanks[/b]