Botanic Gardens Trust, Sydney, Australia

Ceratopetalum (Cunoniaceae)- Phylogenetic relationships

Margaret Heslewood, Project Officer, Molecular Systematics, PhD Student

Molecular data from a number of chloroplast and nuclear loci are being tested for their utility in elucidating relationships within the Cunoniaceae. Broad relationships within the family are well documented, but molecular assessments of finer scale relationships are lacking in many genera and Australian taxa remain poorly represented. Initial sequence data were collected to match existing datasets on GenBank and revealed very low chloroplast divergence across the family at both the rbcL gene and trnL-F intergenic spacer region, both within genera and within tribes. Initial ITS nuclear sequence data however is able to resolve intrageneric relationships. In addition to these loci a number of the proposed barcoding loci are being assessed for variation within the family. Ultimately the molecular phylogenies generated will be calibrated with fossil data to estimate the age and evolutionary origins of taxa within the family.

On a finer scale, population dynamics are being investigated amongst Ceratopetalum species. A set of nuclear microsatellites have been designed to investigate relationships within and between populations of Ceratopetalum species. Nucleotide sequence variation in the flanking regions of these nuclear microsatellites will be examined in the future to determine levels of intra- and inter-specific genetic variation in Ceratopetalum and other Cunoniaceae which will enable detection of phylogenetic structure within species (phylogeographic structure). This data will be used to evaluate the role of long distance dispersal and vicariance in explaining present distributions of Ceratopetalum species.





Collecting Ceratopetalum macrophyllum Noah Creek tributary far north Queensland. Photo: Andrew Ford