Thursday, 1 April 2010

Seed Miles Good for Environment

It was once a bit of a mantra in the restoration trade to source seed from the local area. The closer the better, so that you reintroduce genetic stock very similar to what has been lost.

A scientist from the University of Melbourne is the latest to call for a change this paradigm. If we want to maximise diversity and the ability of plants to adapt to climatic change we should be encouraging mixing of ‘genotypes’. That is, including seed that has travelled a few miles may be better.

The idea is not new. In the Australian Network for Plant Conservation publication Germplasm Conservation in Australia, and its companion Translocation Guidelines, the advice is to generally use 'fairly local provenance for conservation plantings' but to source from large populations and consider including some 'non-local germplasm'. Where possible it's recommended that seeds are sourced from geographcially related and ecologically similar sites so they have a greater chance of survival.

Professor Ary Hoffmann, an ecologist and insect expert, has argued his case in the latest issue of Australian Science, nicely summarised in a media release to Australian Science Communicators.

Hoffman says: “When we re-establish natives in our gardens, along roadsides and in our parks, we should use plants with genes that are going to cope well with conditions in the future. By using mixtures of seeds from local areas and other locations that reflect the future environment, we create a diversity of genes upon which natural selection can act.”

Hoffmann accepts that this will require a change from our current desire for genetic ‘purity’, avoiding mixing populations that are not connected or close. In his view, “The most valuable tracts will contain mixtures of genes and be capable of evolving to deal with future conditions”.

As he explains: “When some individuals survive hot conditions whereas others perish, we are witnessing natural selection and evolution in action. We can help meet this challenge by promoting selection and evolution – increasing the ability of our plant and animal populations to evolve and deal with changing conditions”.

Like all such debates it's a matter of degree. Ideally we can maintain some of the genetically distinct populations that exist today and not have to resort to a homogenous blend just so a species, and habitats, can exist. On the other hand if we zealously stick to local seed only we may, in the longer term, be sending a species extinct.


James C. Trager said...

Here at Shaw Nature Reserve in Missouri, USA, we have a two-fold approach to introducing seeds into a habitat.
-If the site is an unplowed habitat remnant, such as a xeric dolomite grassland or any of our vaiety of oak woodland types, we restrict seed sources to origins of nearly similar geology, ecology, aspect, etc. from within a one-hour's drive, preferably closer.
-If the site is a de novo habitat reconstruction, such as our marsh, wet meadow and tallgrass prairie habitats, we are inclined to go further afield and to prepare seed mixes from as many appropriate sources as possible, allowing the site to sort out the genetics, if you will.

Tim Entwisle said...

That sounds about right James. Like much in life, it's about assessing each situation on its own merit. We tend to go astray when we view the world in black & white - e.g. either any old seed will do, or no seed shall enter this land that hasn't been produced in situ.