Doctoral thesis: On Ingeae Systematics of synandrous mimosoids

  • Date:
  • Location: Zoom Friessalen
  • Doctoral student: Ferm, Julia
  • Contact person: Ferm, Julia
  • Disputation

Background: The Ingeae tribe (Caesalpiniodeae, Fabaceae) has a long history of taxonomic complexity with genera being merged and split, and many species with former placements in several different genera. Moreover, phylogenetic studies have shown that the tribe is non-monophyletic with the genus Acacia (of tribe Acacieae) nested within Ingeae. This problem of non-monophyly is also reflected at the generic and specific level of ingoid taxa. Phylogenetic relationships have been difficult to resolve, with unsettled generic delimitations as a result. In this thesis, I investigated the systematics and phylogeny of the Ingeae-Acacia complex, with reflections on taxonomy and biogeography. Methods: Molecular data of plastid (matK, psbA, trnL-trnF, ycf1) and nuclear (ETS, ITS) DNA sequences were analysed using Bayesian inference and Ultrafast Bootstrap in order to investigate phylogenetic relationships of the Ingeae-Acacia complex. Results: In paper I, Marmaroxylon was shown to be included in Zygia and Zygia inundata in Inga. Marmaroxylon magdalenae, M. ocumarense and Zygia sabatieri were not recovered in the Zygia-Marmaroxylon clade and therefore left without a placement in any genus. In paper II, Zapoteca was shown to be monophyletic but the subgenera comprising more than one species, and four species, were non-monophyletic. In paper III, a new subgeneric classification of Zapoteca and an identification key to the subgenera are presented, as well as a phytogeographical review of the genus. Zapoteca formosa subsp. schottii and Z. formosa subsp. gracilis were recognized as distinct species. In paper IV, Afrocalliandra and Calliandra were recovered as the earliest diverging lineage within the Ingeae-Acacia complex, and the other taxa possessing the same pod-type as Calliandra, i.e. Sanjappa, Thailentadopsis, Viguieranthus and Zapoteca, were shown to be more closely related to each other and other ingoid genera than to Calliandra. Discussion and conclusions: Phylogenetic relationships of the Ingeae-Acacia complex are possible to resolve with a broad sampling and a combination of several nuclear and plastid informative DNA sequences. Taxonomic revisions are, however, needed for several ingoid genera, as well as for the entire Ingeae tribe since it currently is non-monophyletic with respect to Acacia. Shared morphological characters are not always indicative of common ancestry and older morphology-based classifications do not always reflect the evolutionary history of the group. One example is the “Calliandra-pod” fruit type. While it has often been argued to indicate close relationships, I show that this seemingly specific type of pod occurs in several unrelated genera.