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Genetic Provenance

Lesley Waite

"Genetic Provenance" is a subject I knew very little about until I attended an interesting seminar at the Royal Botanic Gardens in August last year which inspired me to do a little bit of research on my own. So the following is my interpretation of the many issues involved in using provenance that goes beyond the notion "you should plant locally-sourced species in or near bushland." Provenance certainly isn't that simple a concept - bush regenerators and revegetators need to be aware of a range of genetic matters and potential problems when considering the source of their seed and the genetic makeup of the plants they use.

So - What is Local Provenance?

Many native plants occur across a broad geographic range. However, within that range, different populations of a particular species may change slightly to become specifically adapted to local conditions and individual habitats. Different populations containing local genetic variations are called provenances. It is important to preserve these different provenances, as each provenance is unique.

Reasons to use Local Provenances

Indigenous plants are the original native plants occurring naturally in a specific area, and there are many benefits in using them to revegetate the local landscape.

1. Better survival mechanisms. The indigenous plants of an area have evolved over a long period of time to suit local conditions such as climate (especially rainfall) and the area's topography and soils. Therefore they have greater survival rates and need less care compared to the same species of plants that have evolved elsewhere. They also tend to be longer lived and being locally evolved, indigenous plants are well suited to unassisted regeneration, reproducing either by seed or by suckering.
   
   
2. Valuable genetic variations. Local provenances often have clear physical differences such as flower colour and leaf shape, but they also may have genetic material whose benefits have not yet been quantified or even discovered - for example the ability to cope with drier conditions or more shade. So the plants from local provenance are more likely to be able to adapt to changes in conditions in their own area.
   
   
3. Distinctive bush character. Because the individual plants are unique to the area, the whole ecosystem that has evolved with them is unique, giving that particular bushland community its own distinctive character.
   
   
4. Ecological Balance. The healthy ecosystem, having evolved as one, also means that there is a strong interdependence both between the plant themselves and with the local native animals, insects, and micro-organisms with which they have evolved, and that all the elements are in balance. Introducing plants/genes that evolved from outside the natural ecosystem risks upsetting that balance. For example, If a non-local species is introduced that has, for example an earlier flowering time than the locally evolved one, the pollinators may finished their pollinating using the introduced species, before the local species has flowered. The local plants may therefore no longer seed, having an adverse impact on both the local species and on its pollinators' lifecycles.
   
   
5. Pest and disease control. Local species provide habitat for local fauna and so can use natural pest control by maintaining balanced populations of predators and parasites that help control pests. Where the coverage and diversity of indigenous plants is changed, resulting imbalances can make the local ecosystem more susceptible to attack.
   
   
6. Weed control. Weed management is fundamental to the success of revegetation projects. Weeds are undesired plants (native or otherwise) that are able to colonise an area by outgrowing competitors and spreading rapidly. Indigenous plants have an important role to play in weed control, where the solution is not just to kill the weeds, but also to fill their niche with desirable plants in balance with the local environment.
   
   
7. Educational tool. Showing the community - children and adults alike - how to propagate, raise seedlings and plant out using local provenance will teach them about and help them better appreciate our local flora and fauna and how they inter-relate.

Some of the genetics-oriented problems to be considered when using local provenances

The idea of using locally-sourced species when bush regenerating was developed in the 1980s. It is only in the last few years that the science of DNA testing and the concept of genetic integrity have been introduced into the equation. Hence the notion of "best practice" is continually evolving. The following is an insight into some of the potential problems.

• Even when using local species, there are risks involved in any bush regeneration, revegetation or landscaping. A key question is, how local is local? It is often quite difficult to collect adequate quantities of seed from a relatively small area. And who knows where the seed really comes from? Roadside and reserve vegetation may well have been planted long ago from seed sourced elsewhere.
  
  
• There is a general lack of remnant vegetation in many areas, and in many remnants the seed resource is extremely low or genetically poor. Or perhaps the season was poor, and produced little seed. Will using such local stock increase the risk of inbreeding and therefore weaken the gene pool?
  
  
• What is the size/status of the gene pool of the area/surrounding areas? Be aware that regeneration can upset the dynamics of an ecosystem by encouraging some species and discouraging others.
  
  
• What connectivity is there between nearby sites? Encouraging pollinators to stay in situ rather than move to other sites has an impact on both sites.
  
  
• How much has the ecosystem changed? Where there has been significant change, local provenance may be less adapted to the new conditions, and no longer be the most suitable choice for revegetation or landscaping.
  
  
• Some councils say new development must have a certain percentage of local native plants. But where does the seed for these plants come from? Particularly if the development is near a threatened ecological community, it may be better to discourage local species because of the potential for hybridisation and loss of unique provenance.

The role of biodiversity

One of the most common topics in conservation at the moment concerns the crisis we are facing in biodiversity. We all need to be more aware of the value of conserving each and every species and indeed each and every variation of species. This variation is crucial to:

• maximizing the long term adaptation potential of the species,
• expanding the gene pool and increasing the potential for evolutionary differentiation (ie. speciation) making the species less vulnerable to sporadic changes in the environment,
• decreasing the risk of inbreeding/lowered population fitness (also known as inbreeding depression),
• decreasing the risk of deleterious genes dominating the gene pool

Our task in bushcare is to maximize diversity through DNA variation (ie. mutations which change the forms of genes-either positively, negatively or neutrally). One important way to do this is to keep apart those species that hybridize easily with one another. The many Australian native species that do hybridise easily will degrade the local gene pool, causing a loss of local adaptations. This in turn decreases biodiversity and causes the species to lose evolutionary potential.

As an example of the using DNA profiles to maintain diversity, Dr Maurizio Rossetto, who is Conservation Geneticist with the Centre for Plant Conservation, Royal Botanic Gardens, talks of a population of Fountainea oraria growing in the Lennox Head area, near Coffs Harbour. This is a former rainforest area affected by development, where there are few mature individuals left. To understand what diversity remains, he looked at the DNA of adults and seedlings. He found that most of the seedlings had the same parent, so there was low diversity, and the likelihood of inbreeding. So in this case, he used propagation material off a variety of adults to increase the variation within the species.

Extra questions to consider if you need to introduce species to a site

When looking at a degraded site that needs planting out, (ie. with revegetation and/or landscaping) ask:

• How well are plants adapted to the site (consider species height, form, flowering times, growth rates, frost resistance, drought tolerance etc) and how the site will react to the plant (consider the plant's shading, root development, pests and diseases, the nutrition it needs or will provide, the habitat it provides etc).
  
  
• What is the status of gene pool of the proposed introduced species?
  
  
• How will this introduced gene pool interact with the existing population? Will it change the ability of existing genes to perpetuate or populate the site? Reduced fitness and other long term effects may occur (remember the importance of reducing the chance of hybridisation).
  
  
• What is the effect of your activities on local pollinators/seed vectors?
  
  
• Is there any research you could do so you don't make mistakes?
  
  
• Where is the best seed bank source?
  
  
• Is there a management strategy in place for the area? Should there be?

Remember that sometimes you can do more harm than good to start without sufficient funding to carry out the right protocols. It is crucial to get the process right. Whether we are talking about whole species or local variants of species, once it has gone, that's it. Extinction is forever!

Developing a plan

There are a lot of people around with good rehabilitation /regeneration skills, and we need to harness those skills by developing an integrated approach, using genetics to make the other disciplines of bushcare more efficient.

A crucial requirement is to look at the big picture. Especially where there are rare and threatened plants or communities, the site needs to be carefully researched to learn provenance boundaries and investigate population dynamics. For example, how fit is the population? How much dispersal is there? How far? Is the fragment size large enough? Then management strategies should be carefully constructed, taking the whole ecosystem into account, remembering that a plant community is not a single species. Then guidelines should be set, changes monitored, and data bases developed on what to plant and where.

So where to from here?

The advances in genetics has opened up the possibilities for bush regenerators to recreate viable ecosystems; conditions whereby pollinators can recolonise an area and cause plant populations to increase and allow for a healthy gene pool. Tackling iconic issues such as Acacia pubescens now seem much more possible.

But there are also many management issues that still need to be worked through to ensure that 'best practice' protocols can be applied. For this it is important to have the right communication channels open to get the best information from the best people. One issue that needs a lot more work concerns the definition of the term 'local'. There needs to be a development of standards by which bushcare workers understand precisely what it means, and can be sure of the integrity of plants or seeds that they access that are labeled 'Local'.

Because of the cost of the research and bushcare activities, and also because of the immense damage that can be done by careless/uninformed bush neighbours, community support is an essential component of bushcare. Perhaps we need to communicate the science of genetic provenance in a more user-friendly way to the community, and help make the environment THEIR issue. One way would be to teach people the principles of using local provenance to provide a continuous food source to keep fauna species moving between bush and their garden. Success from such a project will foster community awareness, with increasing people involvement and positive feedback continuously reinforcing the messages.

Bibliography

Purnell, Kathryn: Landcare Notes - Using Indigenous plants (From the website of the Victorian Department of Primary Industries)

Ralph, Murray: Seed Collection of Australian Plants, 1994

In August, 2002 I attended an interesting seminar at the Royal Botanic Gardens on "Genetic Provenance". The seminar featured Dr Maurizio Rossetto, who is Conservation Geneticist with the Centre for Plant Conservation, Royal Botanic Gardens, Sydney, and Peter Dixon who is a Senior Natural Resource Officer from NSW Dept of Infrastructure, Planning and Natural Resources and President of the Australian Association of Bush Regenerators.

Updated and expanded from the article originally published in Calgaroo, Newsletter of the Australian Plants Society (NSW), Parramatta and the Hills Group; September 2002.

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Australian Plants online - December 2003
Association of Societies for Growing Australian Plants