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The Australian Spermacoceae (Rubiaceae: Rubioideae): systematics, evolution and historical biogeography

Start date:
01 Aug 2015
End date:
30 Jun 2018
Kerry L. Gibbons Marco Duretto Barry Conn
Project sponsors:
Australian Biological Resources Study (ABRS) National Taxonomy Research Grant

Project aims

Using both morphological and molecular phylogenetic techniques, this project aims to:

  • resolve generic limits in Australian Spermacoceae
  • revise species limits in Australian Spermacoce
  • explore the evolution of seed and pollen characters and elaborate petals in Australian Spermacoce.
  • use Australian Spermacoceae to explore the historical biogeography of the Australian Monsoon tropics.

Project Summary

Rubiaceae (coffee family) is the fourth largest family of flowering plants, but remains understudied relative to other groups. In Australia, Spermacoceae is the largest tribe of Rubiaceae, and Spermacoce (c. 100 species) is the largest genus. These herbs occur mainly in the monsoon tropics, a remote region of Australia with a relatively understudied flora. Within Australian Spermacoce, for example, around 30 species still await formal description. International studies have shown that the limits of the genera Hedyotis, Oldenlandia and Spermacoce require revision, but sampling of Australian species has been limited. 

Research Update

International studies have found that Hedyotis, Oldenlandia and Spermacoce each represent more than one evolutionary lineage, and are probably all better recognised as several smaller genera. Two species of Australian Hedyotis are likely to be transferred to Exallage. Although generic names are available to accommodate some Australian species presently placed in Oldenlandia, it is likely at least one new genus will be needed, with Oldenlandia in the strict sense confined to Africa. Australian Spermacoce sampled are related to Spermacoce in the strict sense and other South American species within the group, but few Australian species have been sampled.