Pinus: a model group for unlocking the secrets of alien plant invasions?

The global-scale natural experiment created by the widespread dissemination of most of the 111 species of pines (genus Pinus, family Pinaceae) has shed light on many aspects of plant invasion ecology. Introductions and the fate of alien pines have been well documented worldwide, facilitating the accurate labelling of species as “naturalized”, “invasive”, or “non-invasive” using objective criteria. Thirty species are naturalized and 21 are invasive. Three life-history traits that clearly separate invasive from non-invasive taxa define the inherent ability of species to disperse over long distances, win in competition against other plants, and to survive or proliferate under a range of disturbance regimes. The realization of colonization opportunities for potentially invasive pines is determined by extrinsic factors, especially those that mediate seedling establishment. Meta-analysis of many introduction/invasion events revealed the interplay of factors. Detailed studies of pine invasions have elucidated the roles of long-distance seed dispersal and propagule pressure in driving invasions. Enhanced understanding of the ecology of pine invasions has improved our ability to manage these invasions. No other speciose genus of plants has yielded important insights on so many facets of invasion ecology.