Evidence is presented for phylogenetic relationships in pantropical Melastomataceae, subfamily Olisbeoideae based on combined exon and intron sequences of the nuclear glyceraldehyde 3-phosphate dehydrogenase gene. Parsimony and maximum-likelihood analyses yielded a well-supported ingroup tree consistent with earlier morphologically based concepts of six genera—Memecylon, Mouriri, Votomita, Spathandra, Lijndenia, and Warneckea. The position of the root node in Olisbeoideae remains equivocal. Outgroup-rooted maximum parsimony suggests a deep divergence between Old and New World lineages, while the maximum-likelihood rooting resolved paleotropical genera as a paraphyletic grade basal to the neotropical taxa. The Fitch optimization method for estimating character evolution consistently inferred the strongly acrodromous leaf venation pattern as ancestral in Olisbeoideae, reinforcing the conclusion that the superficially uninervate or brochidodromiform venation pattern of Memecylon, the neotropical subclade, and some Lijndenia and Warneckea species is best interpreted as a series of independent losses of the strongly acrodromous condition. Genomic GapC sequences may have phylogenetic utility at intergeneric level in other angiosperm families, particularly those that have low apparent rates of chloroplast DNA sequence evolution.