• Registered commercial seed stands significantly underrepresent the full bioclimatic diversity found in wild tree populations, potentially limiting the adaptive capacity of planted populations.
• Planted populations have genetic diversity levels comparable to naturally colonised populations, indicating current planting practices largely avoid severe genetic bottlenecks.
• Individuals within planted populations exhibited higher levels of relatedness, increasing the risk of inbreeding and potential loss of genetic diversity in future generations.
• Planted populations displayed higher genetic similarity across sites at regional and supra-regional scales, potentially reducing adaptive differentiation across the landscape.
• Naturally colonised populations showed higher inbreeding, possibly due to fragmented parental populations in degraded landscapes, which may compromise long-term resilience.
• Subtle signals of differential selection and notable differences in health indicators were observed when comparing planted and naturally colonised populations, suggesting that planting protocols may introduce selective pressures that ideally, should be avoided.

Opportunities to improve management of genetic resources

Expand and diversify seed sourcing

The climatic breadth of current commercial seed stands inadequately represent the full bioclimatic diversity of wild populations. Investment in broader networks of registered seed stands and seed orchards would be beneficial for maintaining adaptive diversity.

Address fragmentation effects

Natural colonisation sites often experience elevated inbreeding. This is likely due to isolation and limited gene flow, resulting in a scarcity of parental trees contributing to the genetic pool of newly established populations. Policymakers should consider assisted gene flow, hybrid approaches combining planting with natural colonisation, and improvements in landscape connectivity to mitigate these effects.

Avoid planting populations of closely related individuals

Higher within-site relatedness in planted populations highlights the need to increase the number of regional seed sources and parental trees within commercial seed stands. This would reduce risks of future inbreeding and loss of genetic diversity. Within nurseries, there may also be opportunities to supply batches of saplings that explicitly mix offspring of different sources within a region.

Avoid genetic homogenisation

Higher between-site relatedness among planted populations at regional and supra-regional levels highlights the importance of using seeds from diverse local sources, potentially including the use of local orchards, to preserve genetic diversity across larger geographic scales and reduce risks of genetic homogenisation.

Monitor for unintended selection

Subtle genetic signals suggest that current nursery and planting practices may inadvertently select for specific traits. Monitoring and review of nursery practices may be advisable to maintain resilience and adaptability.

Enhanced knowledge exchange and training

Collaboration between researchers, land managers, nurseries, and seed suppliers is essential to share best practices, address genetic risks and assist researchers in understanding the impacts of industry practice on research findings.