Araceae research projects
The Phylogeny of the Thomsonieae(Araceae) based on DNA sequences
G. B. J. Grob, Dr. B. Gravendeel, W. L. A. Hetterscheid, Dr. M. Roos and Prof. P. Baas - NHN Leiden
The
tribe Thomsonieae (Araceae) consists of two genera: Amorphophallus
Blume ex Decaisne and Pseudodracontium N.E.Br.. Amorphophallus is a large and diverse genus of
geophytes with a wide, palaeotropical distribution. Approximately 200 Amorphophallus species are presently recognised,
some of which are used as food crops. Pseudodracontium
is a small genus consisting of six species only, all occuring in Indochina.
Due to a high variation in morphological characters, the phylogeny of the Thomsonieae has been unclear. In this study DNA sequences are being used to elucidate Amorphophallus relationships. The two prime aims of this molecular study are first, to acquire a robust skeleton phylogeny and second, to determine the phylogenetic status of Pseudodracontium within the Thomsonieae. Although the relationships of the clearly monophyletic Thomsonieae to other Araceae are unresolved, this problem is not particulary addressed in this study.
Until now two chloroplast regions were sequenced: the gene matK, including its downstream spacer, and the intergeneric spacer trnL-trnF. Both DNA regions have been sequenced for 46 representative species of Amorphophallus, two Pseudodracontium species and six possible outgroups. Results based on these datasets indicate that within the Thomsonieae five major clades can be recognized. With one exception, these clades form new hypotheses on intrageneric relationships. The results support both the clear distinction between African and Asian species and the nesting of Pseudodracontium within Amorphophallus.
Presently we try to sequence the nuclear gene LEAFY in order to get an additional and independent molecular hypothesis on the phylogeny of the Thomsonieae. In the near future the molecular, morphological and palynological datasets will be compared and combined in order to get more insight in evolutionary patterns within the tribe.