Print PageMany Australian arid zone plant species have been severely damaged by grazing, loss of pollinators and other impacts and may not survive without urgent intervention. Some exist as small fragmented populations which may lack sufficient genetic variation to reproduce or which may lack functional pollination systems. We are using surveys of demography, pollinator activity and genetic (DNA) diversity, together with experimental tests of self-compatibility in order to identify Acacia species that could benefit from a process of ‘genetic rescue’. Genetic rescue will involve experimental pollinations to produce highly fit seedlings and later transplantion of these seedlings into genetically deficient populations. We are targeting the genus Acacia because existing demographic data shows that that while a small number of species continue to reproduce successfully and are highly fecund, others have flowered consistently for decades while displaying zero or limited seed set. We aim to test the hypotheses that the most fecund species: (1) are serviced by native pollinators (2) are self-compatible and hence less dependent upon inter-population pollen transfers and (3) display high levels of within population genetic diversity. We are also using genetic surveys to target populations and species most appropriate for genetic rescue.
Results/Conclusions
We have detailed comparisons for the reproductively unsuccessful Acacia A. carneorum and the highly fecund Acacia ligulata. Our data only partially match our expectation that seed production by A. carneorum might be limited by the supply of sufficient high quality pollen. Contrary to expectation A. carneorum flowers were visited by a diverse suite of pollen laden native wasps and bees, while for A. ligulata the exotic honey bee Apis mellifera was the only common pollinator. We found that as predicted A. carneorum populations displayed far less genetic diversity than A. ligulata and that each population surveyed was genetically distinct. Unfortunately however, experimental pollen additions provided no basis for a genetic rescue effect in A. carneorum with a range of pollen addition treatments producing no seed set. Again in contrast to expectations we found that A. ligulata is self-incompatible and that pollen sourced from the same or different populations produced similar numbers and quality seed. Intriguingly, 2011 has been the wettest year on record at our sites and produced some surprising outcomes. A. carneorum again displayed reproductive failure but two other species displayed rare episodes of seed set and recruitment, allowing is to use paternity analyses to determine the importance of inter-population pollen transfer.
