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Should we be more critical of remnant seed sources being used for revegetation?

Authors

  • Linda M. Broadhurst,

  • Tom North,

  • Andrew G. Young


  • Linda Broadhurst and Andrew Young are Research Scientists with the Biodiversity and Sustainable Agriculture Program at CSIRO Plant Industry (PO Box 1600, Canberra, ACT 2600, Australia, Tel. +61 26246 4988, Fax +61 26246 5000, Email: linda.broadhurst@csiro.au). Tom North is Australian Co-ordinator for the Millennium Seed Bank Partners (Kings Park and Botanic Gardens, Fraser Avenue, West Perth, WA 6005, Australia). This project arose from observations by Greening Australia field workers that the success of restoration efforts in the Deniliquin region appeared to correspond with the source of seed used.

Abstract

Summary  A challenge for land managers restoring degraded agricultural landscapes across southern Australia will be to ensure the viability of remnant vegetation while simultaneously supplying the quantities of appropriate seed required for revegetation. To ensure such revegetation programs have the best chance of success, seed that is both genetically diverse and locally adapted will be required. Identifying suitable seed sources can be particularly difficult in regions where local seed sources are restricted to small and isolated remnants. Gold-dust Wattle (Acacia acinacea Lindl.) is a key revegetation species in the Deniliquin region of New South Wales; however, broadscale land clearing in the area has limited local seed sources to a few remnant stands. Field-based experience suggests that revegetation success may depend upon the source of seed used, raising the question of whether differences in the germination and survival of seed reflect functional problems within these source populations. To test this possibility, seed was collected from 15 mothers in each of three seed sources regularly used for local restoration programs. Seed quality for each mother was assessed in terms of seed production and seedling fitness. In addition, genetic diversity and mating system parameters were determined to assess whether these explained the seed quality responses observed. Differences among the seed sources with respect to seed quality were generally congruent with field-based predictions. High levels of correlated paternity in the two poorly performing seed sources probably reflect limited mating availability due to smaller population sizes and genetic incompatibility being mediated by a self-incompatible reproductive strategy. Further research is now required to determine whether observed variability in the quality of seed from remnant vegetation in degraded landscapes is compromising revegetation efforts, and to help practitioners develop strategies to critically evaluate their seed sources.

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