Nearly all of the species diversity in Piperaceae is encompassed within Piper and Peperomia. Both genera are pan-tropical with areas of diversification in the Neotropics and Southeast Asia. Piperaceae are less diverse in Africa with only two native species of Piper. This study examines the distribution of both Piper and Peperomia with representative samples from the Neotropics, Asia, Pacific Islands, and Africa. Molecular dating is used to place an age for the crown clades of Piper and Peperomia as well as ages for diversification within the clades. Both genera have origins in the late Cretaceous, but species level diversification occurred much later in the Tertiary. Biogeography of both genera are correlated with paleoclimate evidence to better explain the distribution and diversification of these large genera.

Piper is one of the largest genera of flowering plants. The uniformity of its small flowers and the vast number of species in the genus has hindered the development of a stable infrageneric classification. We sampled 575 accessions corresponding to 332 species of Piper for the ITS region and 181 accessions for the psbJ–petA chloroplast intron to further test previous hypotheses about the major clades within Piper. Phylogenetic analyses were performed for each marker separately and in combination. The ITS region alone resolves eleven major clades within Piper, whereas the psbJ–petA intron fails to recover four of these major groupings and provides no resolution at the base of the phylogeny. The combined analysis provides support for ten monophyletic groups and offers the best hypothesis for relationships in Piper. Our massive ITS dataset allows us to assign confidently a large number of species in this "giant" genus to a major clade. Piper is here divided into ten major clades for which we provide a morphological description. Various clades and subclades are newly identified here: Peltobryon, Schilleria, Isophyllon, P. cinereum/P. sanctum. The clades described here provide a solid framework for future, and more focused, evolutionary studies. New names and combinations proposed herein include Piper bullulatum, P. hooglandii, and P. melchior.