During June and July the Australian Network for Plant Conservation partnered with NSW Local Land Services to present a workshop series by key plant geneticists and practitioners. The workshops covered the current best understanding of native seed provenance issues for planning and implementing ecological restoration, particularly in the face of climate change and vegetation clearing.
Provenances should not be used to define hard boundaries but to develop decision making frameworks that are evolutionarily relevant. Maurizio Rozetto (2015)
Here is a summary of the Orange workshop, which started off by revisiting the crucial question, “what is the definition of local provenance?”
Provenance refers to the place of origin or source of something — eg, a collection; a species, an area containing a population of a species that is assumed genetically distinct from other populations; usually thought to represent genetic adaptation to local environmental conditions. (Driver 2015)
The provenance and local adaptation theory is based on the application of a long-standing precautionary principle which argues that local plants do better than non-local since they are adapted to the local environment. The theory predicts that the further apart populations are geographically, the less likely it is that plants grown from non-local seed will survive.
The concept of plant provenance is not new. It developed in 19th Century forestry science and was adapted for common garden experiments. Provenance is linked to:
- Life history (longevity, breeding system, pollinator and soil interactions);
- Geographic distribution;
And is about knowledge of:
- where plant seed came from,
- the site, soil and situation it grew in,
- the type and form of the plants,
- the number of plants together with other local information.
This knowledge of where seed comes from is all important to its usefulness and value.
Provenance is important to ecological restoration because it influences two major seed sourcing concerns:
- Capturing adaptive evolutionary potential (ie genetic diversity) in changing environments.
- The geographic scale over which seed can be moved, as it affects survival and resilience of plantings and local plant populations, such as:
- Outbreeding depression (poor offspring)
- Superior fitness – weediness potential
- Inappropriate timing – flowering, seed (pollinator time lag) – something not well understood in Australia.
Linda Broadhurst (2015) suggests that Natural Resource Management has commonly looked to protect local vegetation from being “contaminated” by non-local provenance. However, “local” has often been defined and applied without scientific evidence.
For example, it has been common to apply distance based rules such as a 5km radius from the site, but there is no scientific evidence to support such a rule.
Broadhurst (2015) says Australian studies such as Hancock et al (2013, 2014) have found little or no evidence of local superiority germination and initial growth and Pickup (2012) found local populations did better in terms of seedling survival but not biomass and that foreign populations showed improved reproduction.
This suggests that continually collecting from the same small site defined by distance could risk losing genetic diversity through inbreeding. In other words, there is more to provenance than how far away from each other plants are. Soil types, altitude, cliff lines, riparian systems and wind direction, together with the means of pollination (eg insects, birds, wind) are the factors that define plants’ relationships and adaptation.
So, the advice for us is to determine provenance according to the geographical and geological features of the area rather than the proximity of the revegetation site to the collection site. We should collect from populations that are big (400 plants minimum) and healthy, take seed from at least 30 plants within that big, healthy population; and define “local” according to pollinators and geographical features.
This is just some of the key points I gleaned. The full presentations are at: http://www.anpc.asn.au/workshops/provenance
Broadhurst L, (2015) “Provenance issues in a Changing World” National Research Collections Australia/Canberra.
Driver M, (2015) “Provenance Issues in a Changing World”. Presentation to ANPC provenance Workshop, Orange, 2015.
Rozetto, M (2015) “The ‘Provenance Issue’: Challenges and Opportunities for Ecological Restoration”. Power Point presentation to Provenance Workshops; CSIRO & The Royal Botanical Gardens & Domain Trust.