Genus and species boundaries in Lobelioideae
In Australia, the native members of the subfamily Lobelioideae of the Campanulaceae comprise the genera Lobelia, Isotoma and Hypsela. The subfamily Lobelioideae is sometimes treated as a separate family, the Lobeliaceae. Pratia is sometimes recognised as a segregate of Lobelia.
The Lobelioideae includes scrambling to weakly erect perennials, tufted annuals, and erect few-leaved annuals. Nearly all have a distinctive floral structure with two dorsal sepals of distinctly different size and/or shape than the lower three. In a few cases the petals are nearly even. All have milky sap which may be a strong irritant to skin or to the eyes.
There are about 60 species in Australia. Most are endemic in this country, one is shared with New Zealand, and a few others are likely to be common to New Guinea. There are at least 10 unnamed taxa, mostly from south-western Western Australia and tropical northern Australia.
Australia is a centre of diversity for a group of mainly annual species, including many that are strongly stimulated to germinate following fires. Perhaps the best known of these is Lobelia gibbosa. All but one of the members of this distinctive group are endemic to Australia.
There are problems in establishing species limits. There are also considerable problems, both in Australia and worldwide, in defining genera. We are using molecular techniques with morphology to try to resolve the generic limits within the subfamily in Australia.
Eric Knox has sequenced taxa that are representative of all genera in the subfamily and all geographic regions in which they occur. Nearly all the Australian species have been sequenced. The resultant phylogram shows that many of the genera are polyphyletic. Either segregate genera need to be defined or many currently recognised genera should be incorporated into a more broadly circumscribed Lobelia.
One of the most problematic groups contains those species previously referred to Pratia. These are mainly prostrate or procumbent perennials, and are commonly associated with wet sites. An example is Lobelia pedunculata.
- Neville Walsh (Royal Botanic Gardens Victoria)
- David Albrecht (Alice Springs Herbarium)
- Eric Knox (Department of Biology, Indiana University)
Walsh, N.G. and Albrecht, D.E. (2007). Lobelia cleistogamoides (Campanulaceae, subfamily Lobelioideae, Lobelia sect. Holopogon), a new species related to L. heterophylla from Western Australia and South Australia. Nuytsia 17, 397–402.
Albrecht, D.E. (2000). A new species and lectotypification in Campanulaceae: Lobelioideae.Austrobaileya 5, 706–709.
Albrecht, D.E. (1992). A new species of Lobelia L. (Campanulaceae: Lobelioideae) from Victoria and South Australia. Muelleria 7, 525–528.
Albrecht, D.E. (1992). Pratia platycalyx is a synonym of P. irrigua (Campanulaceae: Lobelioideae). Papers & Proceedings of the Royal Society of Tasmania 126, 123–124.