Annonaceae research projects
- Molecular systematics of Annonaceae
- Phylogeny and evolution of Guatteria
- Phylogeny of Miliusa and allied Asian Annonaceae using cpDNA and morphology
- Cremastosperma (and other evolutionary digressions): Molecular phylogenetic, biogeographic, and taxonomic studies in Neotropical Annonaceae
Molecular Systematics of Annonaceae
Dr. L.W. Chatrou - NHN Utrecht
The National Herbarium of the Netherlands houses a large body of specialists
working on the pan-tropical eumagnoliid family Annonaceae. Fibrous and aromatic bark, wood
with fine tangential bands of parenchyma, alternate, distichous leaves, a trimerous
perianth, and ruminate endosperm are among the characters that give Annonaceae their
unmistakable appearance. In the rich forests of the upper Amazon basin Annonaceae always
are among the most important families in terms of number of individuals and species
richness. Some species, such as Annona cherimola (cherimoya), A. muricata
(guanabana, soursop), A. squamosa (sugar apple, sweet apple), and Rollinia
mucosa (biriba) are cultivated throughout the tropics and even subtropics because of
their edible fruit. The strong bark is often used for carrying burdens throughout the
Amazon region. Annonaceous wood is often valued for firewood and is used for poles,
canoes, and bridges. Recently some Annonaceae became important in pharmaceutic research
because of the antifungal, bacteriostatic, and especially cytostatic capability of some
chemical constituents of the leaves and bark.
The Annonaceae have enjoyed quite some attention from systematists in the
20th century. The Swedish botanist Robert Fries spent a lifelong career studying herbarium
specimens, mainly originating from the Neotropics. From 1983 onwards, an international
group of researchers has been assembling loads of data on morphology, anatomy,
reproductive ecology, karyology, and other disciplines valuable for understanding the
evolution of the magnoliid family. Yet when it comes to simply classifying the family,
major problems are facing us. Of the estimated 2500 species that comprise the family, 900
are Neotropical, 450 are African, and the remaining part is Asian. Only recently
Annonaceae in the latter area have started to be examined thoroughly. The knowledge bias
towards Neotropical taxa of the family is brutally hampering our attempts to reconstruct
the family phylogeny. In addition, only few attempts have been made to arrive at a
phylogeny-based classification of the family.
The historical classification by Fries
(1959) has been achieved primarily on the basis of floral characters. Analyses of pollen
ultrastructure and rbcL data refute the higher level taxonomic units in the family
proposed by Fries. Many of the actual phylogenetic studies focus primarily on informal
genus groups. These groups incorporate extant hypotheses on intergeneric relationships,
although their composition has been derived after phenetic analyses. So far, phylogenetic
analyses on the basis of morphological, palynological and molecular data agree on the
position of Anaxagorea as sister to the rest of the family, which is essentially
divided into two main clades. The first clade is supported by inaperturate pollen. The
second clade contains genera with monosulcate and disulculate pollen.
Mindful of the various non-monophyletic genera in need of revision, and of the overrepresentation of Neotropical samples, we have embarked on a project that aims at further unravelling the phylogeny of the Annonaceae and the composition of the two clades mentioned. A phylogeny of approximately 100 species, using trnL-F and rbcL, will be submitted shortly. Collaborators on this project are Paul Bygrave and Mark Chase (Jodrell Laboratory, RBG Kew), Jessica Oosterhof and Henk 't Hart (NHN Utrecht), and Johan Mols and Paul Keßler (NHN Leiden). Meanwhile, we are extending our data matrix by adding matK as a third locus.
Phylogeny and evolution of Guatteria
R.H.J. Erkens MSc, Dr L.W. Chatrou, Dr J. Koek-Noorman and Prof. P.J.M. Maas - NHN Utrecht
The Neotropical genus Guatteria is the largest genus of Annonaceae, comprising 265 species. It is distributed throughout the Neotropics, mainly in wet forest areas, where the species often are key ecological organisms. Because of its evolutionary success, ecological importance, and widespread distribution, this genus potentially provides an important case for the study of speciation processes, key innovations that promoted rapid diversification, and biogeographic processes. This is impeded, however, by major problems concerning taxonomy and classification due to a low morphological and anatomical diversity within the genus. Revision of the genus dates back to Fries’s treatment (1939) and to date Guatteria is the only major genus of Neotropical Annonaceae awaiting revision. Preliminary analyses using rbcL and trnL-F support the monophyly of the genus.
The aim of this Ph.D. project is to arrive at a well-resolved phylogeny of approximately 60 species of Guatteria by using molecular characters from multiple loci, particularly rbcL, rbcL-atpB intergenic spacer, trnL intron and trnL-F intergenic spacer, and matK. Three small genera related to Guatteria, viz. Guatteriella (2 spp.), Guatteriopsis (5 spp.), and Heteropetalum (2 spp.) will be taken into account as well. The resulting scheme of relationships will allow to study patterns of morphological character diversification. Anatomical, and macro- and micromorphological characters (or combinations of these) that are synapomorphic for major groupings within the genus will be looked for. Using these characters, an intrageneric classification will be set up that reflects evolution and has predictive power for the classification of the remaining multitude of species.
Phylogeny of Miliusa and allied Asian Annonaceae using cpDNA and morphology
J.B. Mols, Dr. P.J.A. Keßler and Dr. B. Gravendeel - NHN Leiden; Dr. L.W. Chatrou - NHN Utrecht
Asian Annonaceae are extremely difficult to classify due to diffuse generic circumscriptions. A clear taxonomy is needed as the family is a major component of tropical lowland rainforests and very common in the Flora Malesiana area. Some species also contribute to the local economy by providing timber and fruits.
Tribe Saccopetaleae, presently comprising 6 genera, always seemed a well defined group based on morphological characters like valvate sepals and petals and stamens with connective without prolonged, specialised apex. But recent molecular studies suggests that this tribe is not monophyletic at all.
With this research we try to answer the following questions. Firstly, what are the relationships between the species of Miliusa and is the genus monophyletic. Secondly, is tribe Saccopetaleae monophyletic and what are the relationships between the genera. Thirdly, what are morphological key characters to define specific, generic and tribal boundaries?
To answer these questions both morphological and chloroplast DNA (matK and rbcL gene, trnL intron and trnL-trnF intergenic spacer) data of a large number of Asian Annonaceae genera will be analysed using maximum parsimony.
Cremastosperma (and other evolutionary
digressions): Molecular phylogenetic, biogeographic, and taxonomic studies in
Neotropical Annonaceae
M.D. Pirie, Dr. L.W. Chatrou and Prof. P.J.M. Maas - NHN Utrecht
(see the thesis abstract under Old projects)