The phylogeny and systematics of tribe Acalypheae (Euphorbiaceae)
Kristo K.M. Kulju, P.C. van Welzen, G.C. Zuccarello & P. Baas - NHN Leiden
| Acalypheae is the largest tribe in uniovulate subfamily
Acalyphoideae (angiosperm family Euphorbiaceae). It consists mainly of
trees and shrubs distributed in paleotropics. The tribe has several
economically (Ricinus; source of castor oil), ecologically (Mallotus
and Macaranga; forest disturbance indicators) and ornamentally (Acalypha)
important groups. In my Phd project I'm studying various aspects of the
systematics of tribe Acapheae: 1. Morphological revision of Malesian species of few genera (Cleidion, Neotrewia, Octospermum and Trewia) 2. Phylogeny of Mallotus and related genera. This study aims to clarify the phylogenetic relationships in subtribe Rottlerinae, which comprises two large genera (Mallotus, c. 140 spp; Macaranga, c. 300 spp.) and several smaller satellite genera. Both molecular (plastid and nuclear sequences) and morphological (in co-operation with Soraya Sierra) characters are used for phylogenetic analyses. Preliminary results show Macaranga and some smaller genera embedded inside paraphyletic Mallotus. 3. Phylogeny of tribe Acalypheae. I'm also planning to conduct a molecular phylogenetic study concerning the phylogenetic position of tribe Acalypheae in subfamily Acalyphoideae and intergeneric relationships within Acalypheae. |
Mallotus dispar |
Phylogeny and biogeography of the Malesian species of Mallotus (Euphorbiaceae)
S.E.C. Sierra and Dr. P.C. van Welzen - NHN Leiden
| Mallotus is a large genus of shrubs and trees
with a paleotropical distribution. It comprises approximately 140
species, including several indicators for different kinds of forest
disturbance. The large number of species in combination with the
variability of their morphology has resulted in several different
sub-generic classifications. This shows the
large morphological variability of some of the species and also the
unclear section delimitations. Five (of eight) sections have been
revised by Bollendorff et al. (2000), Slik & van Welzen (2001), Sierra &
van Welzen (in prep). The sections remaining to be revised comprise 41
Malesian species, but in some cases it will be necessary to broaden the
revision and include non-Malesian species. Phylogenetic analyses with morphological (Slik, van Welzen, 2001) and molecular data (Kulju in prep.) suggest that another very species-rich genus Macaranga (c. 250 spp.) is phylogenetically nested inside Mallotus. They also indicate that perhaps part of Mallotus has to be recognised as a separate genus. Therefore another main objective is to provide a phylogeny of Mallotus and representative species of other genera (especially Macaranga), based on morphological characters and if possible combined with molecular characters. The accepted phylogeny will also enable us to answer some ecological and biogeographical questions. For instance, why do we find this genus in Africa? (Mallotus mainly occurs in (sub-)tropical Asia and the Pacific, with only few species in tropical Africa). There seem to be interesting patterns in the distributions. Quite a few Mallotus (like M. philippensis) have widespread distributions, while all other taxa are often extremely endemic (like M. pallidus). This phenomenon does not seem to be limited to Mallotus only, but also other genera of Euphorbiaceae show the same pattern (Sauropus in a completely different subfamily). |
Mallotus konkandae |
The molecular phylogeny of Sauropus and its position within the Phyllanthaceae
Kanchana Pruesapan, Dr. Peter C. van Welzen and Dr. Stefano Draisma - NHN Leiden
|
Sauropus is a genus with about 70 species distributed from Mauritius and India throughout Southeast Asia to Australia. The centres of diversity are in Thailand-Indochina (Sauropus s.l.) and Australia (most species were formerly known as genus Synostemon). Molecular phylogenetic studies of the Phyllanthaceae showed that Sauropus is embedded in the paraphyletic genus Phyllanthus together with its related genera, Breynia and Glochidion (Samuel et al., 2005; Kathriarachchi et al., 2005, in press). Breynia and Glochidion appear to be monophyletic clades, while Sauropus is paraphyletic (due to a ‘Synostemon’ species) and the other sampled species mainly form a polytomy. However, the sampling of Sauropus, Breynia, and Glochidion by Samuel and Kathriarachchi is still very poor. Especially, the delimitation of Sauropus (should Synostemon be included) and the circumscription of infrageneric groups in Sauropus needs much clarification (e.g., the Hemisauropus group may desire generic recognition). The infrageneric classification still seems artificial (Airy Shaw, 1969). The inclusion of Australian Synostemon in Sauropus (Airy Shaw, 1980) does not really clarify the delimitation of the genus. Phylogenetic analyses using morphological and palynological data (Van Welzen, 2003) confirmed that Sauropus is nested together with Breynia and Glochidion in paraphyletic Phyllanthus. The clade showed former Synostemon to be split over Sauropus, Breynia and/or Glochidion. Van Welzen suggests to resurrect former Synostemon, but in a different circumscription (e.g., not including S. bacciformis). Within Sauropus the Hemisauropus group is very distinct and the group with large staminate flowers with the calyx lobes almost completely connected. However, some species seem to be intermediate between the sections. Moreover, Van Welzen showed that morphology alone is far from sufficient to clarify the phylogenetic relationships among the species and genera, a molecular approach is needed. This project aims to make a phylogenetic study that should clarify the infrageneric classification of Sauropus and which should show the position of the genus within Phyllanthaceae by using different molecular markers (plastid matK, nrITS and nuclear PHYC). |
Sauropus androgynus |
