Several species of pines (Pinus spp.; Pinaceae) are highly invasive in parts of the Southern Hemisphere, where pines are widely planted in commercial forestry plantations. Problems associated with the spread of pines from plantations have increased substantially over the past few decades. We review the current extent of the problem and the research that has been undertaken to explain different facets of these invasions, including the factors contributing to species invasiveness and the susceptibility of ecosystems to invasion. Recent interest in producing transgenic pines for wood production raises important issues when considering future scenarios for pine invasions and for sustainable commercial forestry. This chapter considers the genetic diversity in introduced versus native pine populations and then examines the potential for transgene escape from pine plantations in the Southern Hemisphere. Propagule pressure appears to play a major role in these invasions. Commercial plantations have typically introduced a large share of the species’ existing genetic diversity, resulting in rapid adaptation to local conditions and favoring the spread of feral pine populations. The extent to which inherent invasiveness of transgenic pines will differ from non-transgenic pines will depend on the properties conferred by the transgenes, but differences could be substantial. Even subtle changes in species-environment interactions could affect the dynamics of pine invasions. Genetic engineering for reproductive sterility could potentially reduce invasiveness, but criteria for forest certification current prohibit the use of any genetically-modified planting, thus blocking a potentially useful avenue of intervention. Integrated programs for managing pine invasions in the Southern Hemisphere will need to give serious attention to transgenic plantation forestry.
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