Piper globirhachis, a Segregate Species Across the Marañon River Valley, and the Resurrection of Pleiostachyopiper Trel. as a Distinct Subgenus of Neotropical Piper

Abstract

Abstract— Piper globirhachis, a new species from northwestern Amazon, is described and illustrated. It occurs across the Marañon River Valley from its close relative P. nudilimbum with which it has been confounded for ca. 100 yr. Piper globirhachis differs morphologically from P. nudilimbum in having ovate to long-ovate leaf blades and globose inflorescences, vs. elliptic leaves and elongate inflorescences in P. nudilimbum. These species also differ in geographic distribution and ecological niche. A molecular phylogeny based on 135 ITS sequences (125 from Neotropical Piper species and 5 Asian Piper species) enabled the species boundary test (Poisson-tree-processes, PTP) corroborating that these are distinct species. Furthermore, these two species formed a well-supported clade sister to P. subgenus Oxodium (=Schilleria). This phylogeny highlights the importance of allopatric speciation in Piper and provides evidence for the resurrection of Pleiostachyopiper as a subgenus of Neotropical Piper. An identification key for the subgenera of Neotropical Piper is provided.