Conservation biology of holly-leaved grevilleas

Project summary

The 'holly-leaved' grevilleas are an informally recognised assemblage of species found mainly in south-eastern Australia. Our studies focus on factors relevant to the conservation of this morphologically diverse group of species. We are identifying factors limiting distribution and investigating reproductive method, breeding system and habitat loss. We are also assessing genetic variation to improve the understanding of gene flow across each species’ range.

Microsatellite markers for Grevillea infecunda and G. aquifolium are being developed to add to the markers already available for G. macleayana (developed by England et al.) and G. iaspicula (developed by Hoebee).

The first species studied, Grevillea infecunda, was found to be male sterile, thus explaining the lack of seed despite good flowering. This is in contrast to G. renwickiana, restricted to a few sites near Braidwood in New South Wales, which rarely flowers. Genetic analysis of this species has revealed extensive clonality, with fewer than 25 genetic individuals identified. There are also indications of genetic abnormalities. Both G. infecunda and G. renwickiana rely on vegetative reproduction from rhizomes for their persistence.

Gareth Holmes' PhD study, completed in 2009, provided the first phylogeny of the holly-leaved grevilleas. Gareth also carried out a population study of Grevillea repens, which has a disjunct distribution to the east and west of Melbourne. The phylogeny provided some interesting placements of species. For example, G. infecunda was previously considered to be a sterile variant of G. aquifolium, but grouped with the geographically closer species, G. steiglitziana, from the Brisbane Ranges.

Gareth found that populations of Grevillea repens display significant genetic differentiation based on microsatellite data. This supports the hypothesis that eastern and western portions of its range have been historically isolated. Interestingly, these population groups appear to be following different evolutionary trajectories: those from the east show some evidence of mixed ploidy (diploids and triploids) and clonal spread via root-suckers, while western populations appear to be diploid and lack clonal reproduction.

Currently, Trisha Downing from The University of Melbourne is studying relationships within Grevillea aquifolium based on morphological variation (morphometrics), DNA sequence variation and microsatellite variation for her PhD.

Two Honours students at La Trobe University have recently started projects on Victorian Grevillea species: the highly restricted G. obtecta, and G. chrysophaea, the latter a Victorian species more closely related to G. celata than the holly-leaved grevilleas. Both species have informally recognised forms. Molecular markers will be used to compare geographic and genetic distance with the morphological forms.

As we build up information on habitat, genetic variation and reproduction on restricted and more widely distributed grevilleas, we will have a better basis for the design and implementation of recovery plans for these and similar species.

Project team

• Elizabeth James (Royal Botanic Gardens Melbourne)
• Susan Hoebee (La Trobe University)
• Donna McMaster (Department of Sustainability and Environment, Colac)
• Elise Jeffery (Alcoa Anglesea)
• Keith McDougall (NSW Department of Environment and Climate Change)
• Gill Brown (The University of Melbourne)
• Gareth Holmes (former PhD student, The University of Melbourne)
• Trisha Downing (PhD student, The University of Melbourne)
• Gerry Ho (Honours student, La Trobe University)
• Juli Atkinson (Honours student, La Trobe University)
• Pauline Ladiges (The University of Melbourne)
• Ed Newbigin (The University of Melbourne)

Support

• Alcoa
• Cybec Foundation

Publications

Holmes, G.D., James, E.A. and Hoffmann A.A. (2008). Limitations to reproductive output and genetic rescue in populations of the rare shrub Grevillea repens (Proteaceae). Annals of Botany 102, 1031–1041.

Holmes, G.D., James, E.A. and Hoffmann, A.A. (2008). Divergent levels of genetic variation and ploidy among small populations of the rare shrub, Grevillea repens. Conservation Genetics 10, 827–837. doi: 10.1007/S10592-008-9643-9

Kimpton, S., James, E.A. and Drinnan, A. (2002). Reproductive biology and genetic diversity in Grevillea infecunda (Proteaceae), a rare plant with no known seed production. Australian Systematic Botany 15, 485–492.