In an attempt to understand how plants recolonise following fire or drought, a top Californian student is studying with Kings Park scientists to uncover the secret of seed dispersal in Banksia candolleana.

Ms Laura Merwin from Pepperdine University, USA arrived in Australia in September 2008 for 12 months on a prestigious Fullbright Scholarship to studying under the tutelage of Dr Siegy Krauss, Senior Research Scientist in Conservation Genetics at Kings Park and Dr TianHua He from Curtin University.

She proposes to study Banksia candolleana, which are hardy survivors in a harsh climate, at Eneabba, north of Perth. Having completed her Bachelor of Science degree with a major in Biology, 22 year old Laura is undertaking an intermediate research year before returning home to begin a PhD.

'It's really exciting for plant conservation science in WA to be able to attract the brightest and best students from the US, like Laura', said Dr Krauss. 'Fullbright scholarships are highly competitive, and Laura's decision to come here also reflects well on the international quality and standing of the science at Kings Park.'

Laura was attracted to Australia because of its Mediterranean climate, fire and drought prone environment and its ecosystem that is very similar to the one in California. In WA's South West, about 80% of the plant species are endemic and unique to this ecosystem. Like WA, California has high plant biodiversity.

Laura said while species are not the same, plants here have similar adaptations as those in California.

'Plants are the basis of our ecosystems and each relies on the other. If we lost a whole plant species, the effects on the ecosystem could be devastating. Once one piece falls apart other elements will suffer.'

Southern California and South Western Australian shrub species have similar adaptations to drought and fire. Laura believes the most valuable thing to take back to California from this research is the methodology. If similar studies are conducted in California, the data sets can be compared to Australian results.

'This type of comparison can help us understand how these two Mediterranean climate regions are the same and how they are different, allowing us both to develop overarching hypotheses and to identify ways in which each region is unique', said Laura.

With the challenge of climate change significantly apparent, there are more stresses on plants such as changing rainfall patterns, droughts and fires, so how plants recolonise in nature is important to maintaining the species and helping scientists look at conservation efforts generally.

Laura says long distance seed dispersal is important, especially in WA where fire, drought, or other disturbances can cause extinction of local populations. Long distance dispersal can be a way for these species to naturally recolonise these disturbed areas.

'As we deal with climate change and increased human impact, a greater understanding of population structure, for as many species as possible, can help in making informed conservation decisions.

'This region has been chosen because it is a great system in which to conduct population genetics, as it features dunes separated by swales. The Banksia communities occur on the dune crests and each dune can be considered a clearly delineated and natural subpopulation.'

Laura is trying to find out how far seeds are capable of travelling from the parent plant and whether they can travel between subpopulations.

'It is these subpopulations which are most likely to suffer extinction events, so it is important to know whether seed from a nearby surviving subpopulation can recolonise a dune population that has been wiped out', said Laura.

'It's also important to answer the 'how far?' question so that we know what 'nearby' means. Can a subpopulation be naturally re-established by seed from a dune 500 metres away? What about one kilometre? or two kilometres?

'We can do this by creating a genetic profile for each subpopulation using microsatellite DNA, then comparing each individual plant that we've sampled to these genetic profiles. This will tell us the most likely parent population for each plant. Of course, the parent population for most individuals will be the dune it is located on, as most seeds will fall close to their parent plant. However, we are interested in whether there is a small fraction of plants with parents on different dunes, and if so, how big this fraction is and how far away the parent populations are - meters or kilometres? Once we know this, we can try to determine potential mechanisms for this type of long distance seed dispersal.'

Similar studies have already been done on two other Banksia species - Banksia attenuata and Banksia hookeriana. Both these species show a long distance dispersal frequency of around 7%. The results for Banksia candolleana can thus be compared to these species.

'We can establish which is the most likely population the seed originated in, and check how often it's likely that further seed dispersal happens. Once we know the DNA we can pick up individual plants and work out how they are moving.'

One of the theories is that willy-willies assist their dispersal. For other species, emus are important vectors for the long distance dispersal of seeds.

Laura hopes that this study can help conservationists make decisions about how large a conserved area must be to adequately protect a species or community.

'This would also depend on the disturbance regime in the area. A small area subject to frequent fire could be completely burned and be unable to regenerate naturally. A larger area may burn in patches, and long distance dispersal events like those we study might allow recolonisation of burned areas naturally from surviving subpopulations within the conservation area. Of course, there are many, many more aspects to conservation decisions, and one study on one species is just a small part of the vast accumulation of data that goes into making these policies.'

So far Laura has collected 600 samples and is currently working on extracting their DNA.

These studies are important to local scientists and results could be useful with other plant species. Given the recent spate of fires around WA, results could be highly relevant in helping regenerate fire ravaged plant species.


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