TACKLING PANDORA'S BOX - ORDER IN PEPEROMIA

September 2003 to June 2008, PhD thesis

Peperomia, a giant pantropical genus with approximately 1600 species, is characterised by a wide variation in vegetative traits and inflorescence architecture, contrasting with an extreme uniformity in floral morphology. The species concept within the genus is quite narrow and during its history, botanists have been describing many species without much reference to other closely related species. Hence, a user-friendly and surveyable infrageneric classification is essential to gain an overview of the genus.
This study combined a molecular and morphological approach in order to provide a backbone phylogeny of the giant genus Peperomia, serving as a framework for our further research in the genus. The major part of this thesis dealt with studies performed to obtain an overview of the variation within the genus and acquire insight in the relationships between and within infrageneric clades. To start with, a general description of the genus Peperomia is presented, including morphology, anatomy, ecology and nomenclature. The classification of Dahlstedt (1900) has been chosen as a reference and starting point for this study and it was tested with morphological, anatomical, molecular and combined analyses on approximately 60 species of all groups. Morphological data included both macro- and micromorphological observations of all parts of the plants, whereas anatomical data also included crystal studies of the leaves. All these observations were made on living material available from the largest ex situ collection of the genus Peperomia, present in the Ghent University Botanical Garden. Molecular data were based on three markers: chloroplast trnK-matK and nuclear ITS and 26S.

The combination of the different data was performed in order to obtain insight in the evolution of morphological and anatomical characters. The results of all analyses showed that Dahlstedt’s classification is only partially reflecting natural groups as some clades are based on morphological characters which have been subject to parallel evolution. In addition, several new clades have been recovered. Finally, a survey of the names of all infrageneric taxa was made, including typification of the many taxa that had not yet been typified. Incorporation of this and the morphological-molecular data in our ongoing research in the genus will result in a new infrageneric classification that is reflecting phylogenetic relationships. See Peperomia for more information. The second part of this PhD consisted of research in the order Piperales, specifically on the genus Verhuellia. See Verhuellia for more information.
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Relevant publications:
Samain MS
, Vanderschaeve L, Chaerle P, Goetghebeur P, Neinhuis C, Wanke S. (2009) Is morphology telling the truth about the evolution of the giant genus Peperomia (Piperaceae)? Plant Systematics and Evolution 280: 251-254. (erratum)
Samain MS, Vanderschaeve L, Chaerle P, Goetghebeur P, Neinhuis C, Wanke S. (2009) Is morphology telling the truth about the evolution of the giant genus Peperomia (Piperaceae)? Plant Systematics and Evolution 278: 1-21.
Horner H, Wanke S, Samain MS. (2009) Evolution and systematic value of leaf crystal macropatterns in the genus Peperomia (Piperaceae). International Journal of Plant Sciences 170: 343-354.
Samain MS. (2008) Tackling Pandora's Box. Order out of chaos in the giant genus Peperomia (Piperaceae). PhD thesis, Ghent University, Belgium: viii + 270 p.
Mathieu G, Samain MS, Reynders M, Goetghebeur P. (2008) Taxonomy of the Peperomia species (Piperaceae) with pseudo-epiphyllous inflorescences, including four new species. Botanical Journal of the Linnean Society 157: 177-196.
Samain MS, Mathieu G, Vanderschaeve L, Wanke S, Neinhuis C, Goetghebeur P. (2007) Nomenclature and typification of subdivisional names of the genus Peperomia (Piperaceae). Taxon 56: 229-236.
Wanke S, Samain MS, Vanderschaeve L, Mathieu G, Goetghebeur P, Neinhuis C. (2006) Phylogeny of the genus Peperomia (Piperaceae) inferred from the trnK/matK region (cpDNA). Plant Biology 8: 93-102.

Researcher:
Prof Dr. Marie-Stéphanie Samain

Laboratory technician:
Pieter Asselman

Supervisor:
Prof. Dr. Paul Goetghebeur

Collaboration:
Dr. Stefan Wanke - TU Dresden, Germany

Dr. Alexander Vrijdaghs - KULEUVEN, Belgium

Dr. Harry T. Horner - Iowa State University, USA

Funding:
TU Dresden Biology Department, Plant Phylogenetics and Phylogenomics Group, Germany

Friends of the Ghent University Botanical Garden (De Vrienden van de Plantentuin)

Ghent University
Department of Biology
Research Group Spermatophytes
Ghent University Botanical Garden