There are more than three thousand introduced plant species that now call Australia home. The result is that our native ecosystems are being permanently altered. In some systems introduced plants out-compete native species and can cause local extinctions. In other systems, introduced plants can actually increase biodiversity. Some introduced plants are spectacularly bad, and some just quietly co-exist. But all of them are changing our ecosystems, sometimes in ways we can’t yet predict.
My research focuses on the South African beach daisy which arrived in Australia in the 1930’s. I’ve been interested to find out how this plant has been adapting to its new home, and so I’ve been growing South African and Australian plants side-by-side in the glasshouse.
In less than a hundred years this plant has been rapidly evolving changes in nearly every aspect of its biology.
- The South African plants have large, lobed leaves and an upright body shape, whereas the Australian plants have evolved small and smooth juvenile leaves and a longer, creepier body shape.
- The South African plants make a few seeds with their large flowers, but the Australian plants have evolved to produce many more seeds with smaller flowers, and can now do so even without pollen from another plant.
- Both groups are covered in leaf hairs but microscope peels reveal that the Australian plants have evolved 50% more hairs underneath their leaves, making them slower at photosynthesis but more efficient at using water.
- The two groups of plants also defend themselves in different ways, and even flower at different times…a possible precursor for speciation.
Why should we care about all of this…?
Well, the bad news is that if introduced plants are evolving so rapidly then despite our efforts at controlling them they will only become more successful and more invasive as time goes on.
The good news is that if plants in general can evolve so rapidly then perhaps they will be able to adapt to new environmental conditions created by climate change.
I hate introduced species. This beach daisy has come from somewhere else; it’s an unwanted weed that would not be here if humans hadn’t interfered; and it’s growing and spreading along our coast, affecting our native plants and animals.
But what if my research shows that this species was evolving so rapidly that instead of being an unwanted weed it was actually on its way to becoming a unique new species? The Australian beach daisy! Would weed managers pack away the poison and put up a national park instead? Would the public change its mind about introduced species? Would you?
Brandenburger CR, Sherwin WB, Creer SM, Buitenwerf R, Poore AGB, Frankham R, Finnerty PB and Moles AT. 2019. Rapid reshaping: The evolution of morphological changes in an introduced beach daisy. Proceedings of the Royal Society B 286: doi.org/10.1098/rspb.2018.1713.
Rollins LA, Moles AT, Lam S, Buitenwerf R, Buswell JM, Brandenburger CR, Flores‐Moreno H, Nielsen KB, Couchman E, Brown GS and Thomson FJ. 2013. High genetic diversity is not essential for successful introduction. Ecology and Evolution 3: 4501-4517.
Hoffmann JH, Impson FAC and Volchansky CR*. 2002. Biological control of cactus weeds: implications of hybridization between control agent biotypes. Journal of Applied Ecology 39: 900-908.
Volchansky CR*, Hoffmann JH and Zimmerman HG. 1999. Host-plant affinities of two biotypes of Dactylopius opuntiae (Homoptera: Dactylopiidae): Enhanced prospects for biological control of Opuntia stricta (Cactaceae) in South Africa. Journal of Applied Ecology 36: 85-91.
*Volchansky is my maiden name