A collaborative project undertaken at the Australian Tropical Herbarium, James Cook University and supervised by Katharina Schulte and Darren Crayn
Australia’s biodiversity is characterized by a rich endemic flora of terrestrial orchids. Tribe Diurideae (over 900 species) comprises several lineages that underwent major radiations on the continent, such as in Caladeniinae, Prasophyllinae, or Thelymitrinae. Diurid orchids display striking morphological plasticity, which is often difficult to interpret and which has led to highly divergent classifications for the group. In particular, generic classification of the Diurideae is highly controversial, with different authors recognizing between 38 and 59 genera within the group. So far, standard molecular markers have provided only limited insights into phylogenetic relationships of diurid orchids, and we still lack a robust phylogenetic framework for the tribe.
Figure 1. Caladenia flava (photo Katharina Schulte)
Figure 2. Corybas barbarae (photo Tapio Linderhaus)
Figure 3. Diuris magnifica (photo Katharina Schulte)
In this project we used next-generation sequencing technologies to reconstruct evolutionary relationships in Australia’s largest group of terrestrial orchids, the Diurideae. Our phylogenomic analysis based on more than 70 plastid genes and including over 90% of the described genera within the tribe yielded a well-resolved and supported phylogeny. Character trait mapping based on our plastome phylogeny increases our understanding of morphological character evolution within Diurideae, and allows for an evaluation of the taxonomic value of key characters. Our molecular phylogeny also constitutes an important framework for the re-assessment of subtribal delimitations and controversial generic concepts in Diurideae, as several of the previously recognized subtribes and genera were found to be paraphyletic. Further, our molecular dating analysis provides the first detailed insights into the temporal evolution of this important Australasian orchid tribe.
Our plastome data set for Diurideae provides highly valuable genetic resources (incl. DNA barcode markers) for Australia’s terrestrial orchid flora, which will be made available through online portals such as Genbank upon the publication of the results of this study.
This project was carried out in collaboration with Mark Clements (Centre for Australian National Biodiversity Research) and Peter Weston (Royal Botanic Gardens and Domain Trust Sydney).