Systematics of Malesian-Pacific Piper (Piperaceae)

• Main Author: Asmarayani, Rani
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2019
• Subjects: Systematic biology
• ISBN: 9781085592352; 1085592359

Comprised of ~2400 spp., Piper is a major clade in the magnoliid angiosperms. Three major groups are recognized in Piper, i.e., the Neotropical, Asian and South Pacific. Unlike Neotropical Piper, relationships in the Paleotropical Piper remain enigmatic. This study focused on the Paleotropical Piper with emphasize on the Malesian-Pacific Piper, Malesia being the center of diversity of the genus in the Paleotropics. The goals are to evaluate relationships within Paleotropical Piper (chapter 1), to evaluate characters, morphological (chapter 1) and stem anatomical (chapter 2), that may distinguish clades, and to investigate the species boundaries focusing on the well-supported Muldera clade emphasizing the Malay Peninsula species (chapter 3). I used eleven out of 14 infrageneric groups in Paleotropical Piper and 14% of the species and inferred their phylogenetic relationships based on nuclear (ITS, g3pdh) and chloroplast (trnL-F) regions. Within the Asian clade, species predominantly distributed west of Wallace’s Line (WWL) form a moderately/strongly supported clade in the ITS phylogeny, embedded within a grade of species from east of Wallace’s Line (EWL). The ITS phylogeny also resolves 12 and 5 clades in the WWL clade and the EWL grade, respectively. G3pdh and trnL-F phylogenies resolve some of the same clades, but some relationships among and within clades are incongruent. Almost no currently recognized infrageneric groups in Asian Piper are monophyletic. Most of the morphological characters previously used to delimit infrageneric groups are homoplasious, and I also found that there is much parallelism in the stem anatomical characters. Characters that may distinguish clade include cupular bracts and a ring of sclereids surrounding sclerenchymatous cap of peripheral vascular bundles of the stems for Muldera clade, angular stems for Sarcostemon s.l. clade, very broad primary medullary rays in the stems for Pseudochavica sensu Ridley s.str. clade, spherical stigmas for core E2 clade, and peripheral mucilage canals interior to the large vascular bundles in the stems of E1 clade. The species limits within Muldera clade remains unclear, there are some shared characters between morphospecies and common occurrence of paraphyly, suggesting hybridization or lateral transfer among species of Muldera clade.