Best-scoring maximum likelihood phylogram. Clade support values (LB: likelihood bootstrap/PB: parsimony bootstrap/PP: posterior probability) larger than 50% are indicated at each node. Dashed branches indicate LB, PB, and PP all smaller than 50%/0.5 while thick branches denote those present in the strict consensus tree of MP analysis and PP ≥0.95. Species in bold denote limestone species distributed in the Sino-Vietnamese limestone karsts (Gu et al.,2007). Arrows point to clades and sections discussed in the text. Taxon names are followed by sectional placement and distribution (in parentheses). The rhombus (◇) and star (☆) signs denote calibration points for molecular dating. Sectional classification and clade names in Thomas et al. (2011a) are marked to the right to allow easier cross-study comparison. Sources of sectional placement for each species are cited in Additional file1. Sectional abbreviations: ALI: Alicida, AUG: Augustia, BAR: Baryandra, COL: Coelocentrum, DIP: Diploclinium, HAA: Haagea, LEP: Leprosae, PAR: Parvibegonia, PET: Petermannia, PLA: Platycentrum, REI: Reichenheimia, RID: Ridleyella, SPH: Sphenanthera, SYM: Symbegonia, UA: unassigned.