RESEARCH ARTICLE High Levels of Genetic Contamination in Remnant Populations of Acacia saligna from a Genetically Divergent Planted Stand Melissa A. Millar, 1,2,3,4 Margaret Byrne, 2,3 Ian K. Nuberg, 1,2 and Margaret Sedgley 5 Abstract It is essential to understand the patterns of pollen dispersal in remnant vegetation occupying highly disturbed land- scapes in order to provide sustainable management options and to inform restoration programs. Direct and indirect methods of paternity analysis were used to detect genetic contamination via inter-subspecific pollen dispersal from a planted stand of nonlocal Acacia saligna ssp. saligna (ms) into remnant roadside patches of local A. saligna ssp. lind- leyi (ms). Genetic contamination was detected in 25.5% (indirect paternity assignment) to 32% (direct paternity assignment) of ssp. lindleyi progeny and occurred over a distance of 1.6 km. The results support studies that suggest genetic continuity is maintained by high levels of pollen dispersal in temperate entomophilous species. The results also indicate that patchily distributed remnant populations may be exposed to substantial amounts of genetic con- tamination from large-scale restoration with native taxa in the highly fragmented agricultural landscape of south- ern Western Australia. Management practices to reduce the risk of genetic contamination are considered. Key words: fragmented vegetation, gene flow, genetic con- tamination, paternity analysis, pollen dispersal, risk assess- ment. Introduction Populations of remnant vegetation occupying highly anthro- pogenically disturbed landscapes are often fragmented in com- parison to pre-disturbance conditions. Disturbance typically results in decreased population size and density and increased population isolation due to geographical distance or physical barriers in the landscape (Kwak et al. 1998). Fragmentation may also be expected to result in reduced levels of interconnec- tivity in terms of pollen-mediated gene flow among remnant vegetation (Ellstrand 1992; Young et al. 1996; Kwak et al. 1998). Young et al. (1996) and Lowe et al. (2005) review the effects of reduced levels of gene flow on the genetics of iso- lated populations following habitat fragmentation. However, as Lowe et al. (2005) point out, a number of studies, predom- inantly on forest tree species, suggest that extensive levels of pollen dispersal can be maintained across populations in fragmented landscapes. The maintenance of high levels of 1 School of Agriculture, Food and Wine, The University of Adelaide, Adelaide, 5005 SA, Australia 2 Future Farm Industries CRC, The University of Western Australia, Crawley, 6009 WA, Australia 3 Science Division, Department of Environment and Conservation, Locked Bag 104, Bentley Delivery Centre, Bentley, 6983 WA, Australia 4 Address correspondence to M. A. Millar, email melissa.millar@dec.wa.gov.au 5 Faculty of the Arts and Sciences, The University of New England, Armidale, 2351 NSW, Australia  2010 Society for Ecological Restoration International doi: 10.1111/j.1526-100X.2010.00758.x pollen dispersal may have positive effects for the persistence of small remnant populations, but the findings also increase concern regarding the risk of genetic contamination from non- local taxa introduced to highly fragmented landscapes (Ledig 1992; Difazio et al. 2004). Genetically divergent, nonlocal taxa may be introduced to the range of local native species either through naturalization processes or intentional plantings. Where plantings are aimed at the restoration of compositional and functional biodiversity the use of “local provenance” material is advocated as an ele- ment of the precautionary principle. For projects with different aims, and for those that must compete commercially with exist- ing land use, the use of local material may be unfeasible. In such cases, genetic divergence between native remnants and introduced taxa may be due to deliberate use of nonlocal mate- rial, or may arise from selection pressures applied in breeding and domestication programs (Byrne & Millar 2004). Across southern Australia the majority of native vegetation has been cleared for agriculture. Remnant vegetation now largely comprises small populations in nature reserves or strips along roads and fence lines. Large-scale revegetation of this landscape is required in order to restore essential ecosystem services and combat increasing dryland salinity. Restoration programs must compete commercially with current agricultural land use and a number of native species are being developed for commercial agroforestry (Bartle 1991; Olsen et al. 2004). There are significant advantages in using native species as they are adapted to the harsh environment and nutrient-deficient 260 Restoration Ecology Vol. 20, No. 2, pp. 260–267 MARCH 2012