The potential for gene flow from exotic eucalypt plantations into Australia's rare native eucalypts

Progress in Myrtaceae genetics and genomics: Eucalyptus as the pivotal genus

“…Observed heterozygosity (individual heterozygosity), however, was consistently higher in the breeding population than in native trees, suggesting that heterozygotes have been preferentially selected within the program . Markers have been successfully used to estimate outcrossing rates, study parentage, and outside pollen contamination in seed orchards, parameters that have also been valuable to provide general guidelines for risk assessment of gene flow from plantation to natural stands (Barbour et al 2010;Burczyk et al 2002;Chaix et al 2003;Gaiotto et al 1997;Jones et al 2008;Patterson et al 2004;Rao et al 2008). In breeding programs, DNA paternity testing was successfully employed to retrospectively select parents of higher specific combining ability and demonstrate realized gains in volume growth above 24% in commercial forest stands (Grattapaglia et al 2004b).…”

Managing Australia’s eucalypt gene pools: assessing the risk of exotic gene flow

“…The F 1 hybrid seedlings are, therefore, generally detectable through visual inspection of open pollinated progeny grown from seed collected from the native trees, whether this be following supplementary (Barbour et al 2005a) or natural (Barbour et al 2002) crossing. This methodology is very efficient and has been validated using: (i) controlled crossing (where flowers were emasculated and isolated - Barbour et al 2005a); (ii) molecular markers (Barbour et al 2002;Barbour et al 2010); and (iii) near-infrared reflectance spectroscopy (Humphreys et al 2008;O'Reilly-Wapstra et al 2013). The morphological differences between exotic F 1 hybrids and the native species at the seedling stage have been documented to facilitate operational risk assessments (Barbour et al 2005a;Roberts et al 2009).…”

“…A similar plantation buffer distance is now being tested in what was predicted to be one of the highest risk situations in Tasmania. This case study will be used to inform an adaptive management strategy associated with the development of a E. nitens plantation estate of nearly 600 ha in the landscape surrounding a small reserve of one of the three populations of E. perriniana in Tasmania (Barbour et al 2010;Larcombe et al 2012). At the beginning, a small plantation of 60 ha of E. nitens was situated 630 m away from the E. perriniana population, but subsequent plantings were done up to a 500 m buffer distance around the E. perriniana population.…”

“…For example, in a survey of 302 plantations across the E. globulus estate from Tasmania to south-west Western Australia, Barbour et al (2008b) found only 21 Symphyomyrtus species growing adjacent to those plantations. In a related study, a desktop analysis of point records for rare and threatened eucalypts found that of the 74 nationally listed rare eucalypt taxa only eight occurred within 1 km of a eucalypt plantation (Barbour et al 2010), and only four of Figure 3: Cross compatability between E. globulus and species from across subgenus Symphyomyrtus has been estimated using a supplementary crossing approach. This involves applying E. globulus pollen to open flowers without isolation so that the exotic pollen can compete with intraspecifc pollen.…”

Thank you for not flowering: conservation genetics and gene flow analysis of native and non-native populations of Fraxinus (Oleaceae) in Ireland

“…Afforestation and reforestation programmes are among the largest sources of genetic contamination of local populations when there are weak barriers to intra-or interspecific gene flow between introduced and local individuals (Barbour et al, 2010;Meirmans et al, 2010;DiFazio et al, 2012). In such programmes, hundreds of hectares are often planted with very few species at a high density, and thus the introduced trees are sources of a huge amount of pollen.…”