Supervisor: Linda Broadhurst
Background
Broad scale land clearing to support agriculture since European settlement has contributed to the fragmentation and deterioration of most natural vegetation communities across Australia. Not only has this resulted in biodiversity losses, but it has also altered many of the ecosystem services previously provided by deep-rooted perennial vegetation. For example, dryland salinity is now a noticeable component in many agricultural landscapes with approximately 5.7 million ha currently affected, increasing to an anticipated 17 million ha by 2050. Accordingly, remediation within agricultural landscapes is a now an urgent national priority. However, the scale on which revegetation is needed presents problems for those organizations and community groups charged with this undertaking. Large volumes of good quality seed are required to not only ensure initial establishment but also long-term population viability in terms of genetic diversity and mate availability.
Ironically, in those regions where revegetation is most urgent, the quality of local seed sources has been compromised by long-term fragmentation. Remnants where seed collection can be undertaken are in serious danger of over-exploitation. While the movement of seed suitable for revegetation from one region to another may alleviate some of these problems, seed translocation is often restricted by concerns associated with seed provenance and there is a general reluctance to move seed far from its original collection point. Such concerns are focused on the idea that locally adapted seed may be unable to survive or will perform poorly in new environments, negating any advantages of using outsourced seed. Until the issues associated with provenance are better understood, many organizations such as Greening Australia (GA) continue to work within a high cost framework that restricts seed movement and necessitates long term storage of large segregated seed collections.
The Murray Darling Basin (MDB) is one of Australia’s largest river systems, stretching across four mainland states with much of the surrounding land being used for agricultural production. However, as both water requirements and land clearing have increased, changes to the hydrological cycle have occurred and salt previously stored in the soil profile is now being mobilized. To help alleviate problems associated with increased soil salinity in this landscape, several revegetation programs have been initiated. An important species targeted for broadscale revegetation by GA (Vic) is Acacia acinacea (Mimosaceae), which grows widely across much of southeastern Australia, and in particular within the MDB. This species plays an important role in a structural context and as a nitrogen-fixer and consequently has the potential to facilitate growth of many other species, thereby improving revegetation success. Two discrete morphological entities are recognised by GA (Vic) and there are significant costs differentials associated with their collection, storage and use. If provenance is not a significant issue for this species, considerable savings could be made by GA (Vic).
To better understand the role of provenance in A. acinacea, seed collections from 37 populations across the geographic distribution were supplied by GA (Vic) for demographic and genetic analyses. During a fitness trial conducted earlier this year to assess germination, growth and survival, it became apparent that three broad forms could be identified according to leaf shape and habit. In addition, chromosome counts have indicated that some populations are polyploid which may limit their utility as potential seed sources.
Approach
This project will further explore variation among A. acinacea populations using both genetic and morphological markers. Allozyme markers will be used to determine levels of genetic diversity within populations as well as to assess whether there is any population structure associated with geographic range. Morphological characters will be assessed in conjunction with Maurice McDonald (CSIRO FFP) using specimens collected at the conclusion of the growth trial. Following data collection, multivariate statistical techniques will be used to determine whether the forms observed during the growth trial represent discrete morphological entities and if so, do these have a geographic or regional basis? The student undertaking this project will contribute significantly to a better understanding of provenance issues present within A. acinacea. It will provide an opportunity for the student to develop useful genetic skills as well as an understanding of multivariate statistical techniques. For GA (Vic) it will provide a better understanding of the variation present within A. acinacea and may result in significant cost savings associated with seed translocation and segregation of collections.