Estimating exotic gene flow into native pine stands: zygotic vs. gametic components

Area of Science:

• Ecology
• Genetics
• Conservation Biology

Background:

• Contemporary gene flow from exotic plantations poses challenges for forest conservation genetics.
• Distinguishing zygotic, male gametic, and female gametic gene flow is critical but often overlooked in plants.
• Existing models primarily estimate zygotic and male gametic gene flow.

Purpose of the Study:

• To develop and apply a novel method for estimating all three components of exotic gene flow: zygotic, male gametic, and female gametic.
• To quantify gene flow rates from exotic plantations into native maritime pine (Pinus pinaster) and Scots pine (Pinus sylvestris) stands in Iberia.
• To assess the conservation implications of contemporary genetic introgression.

Main Methods:

• Developed a new model combining uni- and biparentally inherited markers to estimate female gametic gene flow.
• Utilized a combination of chloroplast (maternal) and nuclear microsatellites for gene flow estimation.
• Applied the model to estimate gene flow from exotic plantations into two Iberian relict pine stands.

Main Results:

• Observed moderate male gametic introgression (6-8%) from exotic to native pine stands for both species.
• Found no evidence of zygotic or female gametic gene flow, indicating pollen dispersal but not seed dispersal from exotic sources.
• Numerical simulations confirmed the model's accuracy, particularly with larger sample sizes.

Conclusions:

• Contemporary gene flow from exotic plantations is primarily driven by pollen dispersal, not seed dispersal.
• Understanding these distinct gene flow pathways is essential for effective forest conservation and management strategies.
• The developed approach provides valuable insights for managing genetic connectivity and potential risks associated with nonlocal genes.