Modeling seed dispersal distances: implications for transgenic Pinus taeda

Area of Science:

• Ecology
• Genetics
• Forestry

Background:

• Assessing gene flow from genetically engineered (GE) or transgenic trees is vital for biocontainment.
• Field trials for transgenic forest trees are increasing, particularly in the Southeastern US with Pinus taeda (loblolly pine).

Purpose of the Study:

• To model and predict forest-tree seed dispersal distances for estimating gene flow from transgenic trees.
• To evaluate the potential for long-distance dispersal (LDD) and its implications for biocontainment zones.

Main Methods:

• Simulated seed dispersal using a model incorporating forest canopy height, seed terminal velocity, release rate, and turbulent-flow statistics.
• Collected data from a Pinus taeda plantation in Duke Forest, North Carolina.
• Analyzed seed dispersal patterns in 16- and 25-year-old plantations.

Main Results:

• Most seeds dispersed locally (0.05–0.14 km) from the source.
• A fraction of seeds underwent LDD, traveling up to 33.7 km.
• Approximately 70 seeds/ha were predicted to travel over 1 km, exceeding a viable biocontainment zone.
• The probability of LDD exceeding 1 km for transgenic conifer seeds approached 100%.

Conclusions:

• Local dispersal is common, but LDD poses a significant risk for biocontainment of transgenic forest trees.
• Current biocontainment strategies may be insufficient given the potential for long-distance seed dispersal.
• Further research is needed to refine LDD predictions and develop effective biocontainment measures for transgenic forest trees.