Peter van Welzen

Peter van Welzen

My research focus has two directions: the species of the family Euphorbiaceae in Malesia (and local SE. Asian floras) and the distributions of plants in SE Asia, which patterns can be found and how to explain them.


Biogeography, Climate change, Dipsersal pathways, Distribution patterns, Euphorbiaceae, Flora Malesiana, Plate tectonics, Sapindaceae

Prof. Dr. Peter C. van Welzen

Chair tropical plant biogeography
Senior researcher
Tropical Botany
+31 (0)71 751 9205

Malesian Euphorbiaceae
Thai Euphorbiaceae
Malesian collectors


Where does the Malesian flora originated from, which species does it contain, which distribution patterns and pathways did it develop and will these pathways prevail under climate change?

The islands of the Malay Archipelago (Malesia) came together during the last 55 Ma. The c. 50,000 fern and flowering plant species are still largely unknown. My first interest is to elucidate many of these species, especially in the Euphorbiaceae and closely related families (Pandaceae, Peraceae, Phyllanthaceae, Picrodendraceae), about 1500 species. The species mainly originated in Malesia, but their ancestors must have come from either Laurasia or Australia. Which pathways did these ancestors take? Which general distributions patterns did they use? Many species, also the unknown ones, are under threat due to overpupulation, land use and climate change. If they like to disperse to better circumstances will the former pathways still be available or will there be alternatives?

Acalypha wilkesiana
Distribution Macaranga & Mallotus


A selection of the topics I am working on currently.


Revision of the genus Claoxylon (Euphorbiaceae)

Which species are present in Malesia? Where and under which circumstances do they occur? How to recognize them? Typical for this genus is the sandpaper feeling of the dried leaves, which is caused by needle-like crystals that protrude the surface after…
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Weda, a new genus of Euphorbiaceae

Material collected during an environmental impact study for a proposed nickel mine along Weda Bay on Halmahera in the North Moluccas of Indonesia revealed one unknown Euphorbiaceae with a very unique combination of characteristics. Based on the…
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Historical Biogeography Mallotus peltatus

Historical biogeography of Malesia

Historical biogeography reconstructs distributions in the past (those of ancestral species). Purpose is to see where various groups originated and how they dispersed over the Malay Archipelago and adjacent areas. The final goal is to see from which areas…
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Euphorbiaceae phylogeny Jatropha gossypiifolia

Phylogeny of Euphorbiaceae

The Euphorbiaceae used to be a very big family, but recent molecular studies showed that only those species with a single ovule (egg)/seed per chamber in the ovary/fruit are real Euphorbiaceae. This reduced the family to roughly half of its former size…
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Moth pollination Breynia discocalyx

Moth pollination in Phyllanthaceae

Several groups in the Phyllanthaceae live in symbiosis with moths. The moths pollinate the flowers, and their larvae are harboured by the fruits and can feed on part of the seeds. This symbiosis results in drastic adaptations in the male and female flowers…
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Flower field

Blumea journal

Blumea is an international electronic-only journal on the biodiversity, evolution and biogeography of plants, including systematics, floristics, phylogeny, morphology and anatomy.
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  • van Welzen PC, Strijk JS, van Konijnenburg-van Cittert JHA, Nucete M, Merckx VSFT. 2014. Dated phylogenies of the sister genera Macaranga and Mallotus (Euphorbiaceae): Congruence in historical biogeographic patterns?. PLOS ONE 9: e85713 (
  • van Welzen PC, van Oostrum AF. 2015. Revision of the Malesian species of Dimorphocalyx (Euphorbiaceae). Blumea 59: 191–201 (
  • van Welzen PC, Pruesapan K, Telford IRH, Bruhl JJ. 2015. Historical biogeography of Breynia (Phyllanthaceae): what caused speciation? Journal of Biogeography 42: 1493–1502 (
  • Van den Ende C, White LT, van Welzen PC. 2017. The existence and break-up of the Antarctic land bridge as indicated by both amphi-Pacific distributions and tectonics. Gondwana Research 44: 219–227 (
  • Rutgrink ALJ, Visser M, van Welzen PC. 2018. Differences between the floras of the North and South Moluccas (Indonesia). Journal of Sytematics and Evolution 56: 652‒662 (
  • Bouman R, van Welzen PC, Sumail S, Echevarria G, Erskine PD, van der Ent A. 2018. Phyllanthus rufuschaneyi: a new nickel hyperaccumulator from Sabah (Borneo Island) with potential for tropical agromining. Botanical Studies 59 (9): 1‒12 (

All publications


Naturalis aims to be a breeding ground for international scientific talent. Therefore, PhD's have a special position in our organisation.

    • Mega Atria
    • Roderick Bouman
    • Abdulrokhman Kartonegoro
    • Anneke Madern
    • Héctor Ortega Salas
    • Renyong Yu


    • Coordinator of M.Sc./Ph.D. course 'Plant families of the tropics', first 3 full weeks in January in Hortus botanicus
    • Phylogeny part (1 week) in B.Sc. course 'Evolution biology'
    • Biogeography part (c. 1 week) in M.Sc./Ph.D. course 'Integrative Taxonomy'
    • Lecture 'Global patterns in terrestrial biogeography' in course 'Ecology 2' by CML
    • B.Sc. internships
    • M.Sc. internships