A molecular and morphological phylogeny of the Phebalium Group (Rutaceae): resolving the status and relationships of taxa of high conservation value

A project undertaken at the National Herbarium of New South Wales, Royal Botanic Gardens and Domain Trust, and supervised by Dr Marco Duretto and Dr Michael Bayly (Uni. Melb.).

Background

The Phebalium Group (10 genera, 111 spp) represents a significant component of biodiversity in the plant family Rutaceae. Rutaceae is a Southern Hemisphere family that is well represented in Australia (43 genera, 24 endemic; 486 spp., 458 endemic) and eastern and south-western Australia are major centres of diversity. The Phebalium Group is largely confined to southern Australia although three genera have species present in the tropics (NT, N Qld), and one species is endemic to New Zealand.


All genera have been revised at the species level though there are still discrete species complexes to be resolved and several undescribed taxa. No genera have a published phylogeny or a formal infrageneric classification. The lack of understanding of the relationships between and within these genera is a significant gap in our knowledge of the systematics of Australian Rutaceae hampering further research on the group.


Only one genus is clearly defined and generic rearrangement appears to be required that may include the recognition of new genera.  Morphology provides useful data but the phylogenetic signal is obscured because of the large number of species and the highly derived nature of many taxa. Interestingly, many of the generic issues centre on rare species with restricted and/or disjunct distributions. To resolve these issues confidently what is required is a multi-gene phylogeny that includes the majority of species in all genera.


Aims


In this study we aim to produce the first robust phylogeny of the Phebalium Group which will be used as a framework to define generic and infrageneric limits. We will critically evaluate the taxonomic status of several taxa that are isolated, taxonomically and/or geographically.


We will do this by:

  1. Producing robust molecular phylogenies based on multiple gene sequences for all genera and the majority of species.
  2. Producing molecular phylogenies for the larger genera with identified taxonomic issues, viz. Phebalium, Leionema and Nematolepis.
  3. Mapping morphological characters onto these phylogenetic trees to determine the evolution of key features such as seed morphology and pollination biology and delimit genera and subgeneric taxa based on natural groups.
  4. Identifying congruent biogeographic patterns across Australia, especially in southern Australia, using multiple genera and identifying areas and taxa of high conservation value.
Figure 1. Phebalium squamulosum subsp. squamulosum (Ku-ring-gai Chase National Park, New South Wales)

Figure 2. Diplolaena sp. (Mt Lesueur National Park, SW Western Australia)

Figure 3. Asterolasia correifolia(Ku-ring-gai Chase National Park, Sydney, New South Wales)