Natural recovery of genetic diversity by gene flow in reforested areas of the endemic Canary Island pine, Pinus canariensis

TL;DR

This study shows that gene flow from natural to reforested Canary Island pine stands can significantly restore genetic diversity, highlighting natural recovery processes in reforestation efforts.

Contribution

It provides evidence that natural gene flow can recover genetic diversity in reforested areas of Pinus canariensis, emphasizing the importance of surrounding natural stands.

Findings

High immigration rates into reforested stands (0.68-0.75)

Genetic diversity increased in reforested stands due to gene flow

Chloroplast markers showed lower diversity, indicating bottleneck effects

Abstract

The endemic pine, Pinus canariensis, forms one of the main forest ecosystems in the Canary Islands. In this archipelago, pine forest is a mosaic of natural stands (remnants of past forest overexploitation) and artificial stands planted from the 1940's. The genetic makeup of the artificially regenerated forest is of some concern. The use of reproductive material with uncontrolled origin or from a reduced number of parental trees may produce stands ill adapted to local conditions or unable to adapt in response to environmental change. The genetic diversity within a transect of reforested stands connecting two natural forest fragments has been studied with nuclear and chloroplast microsatellites. Little genetic differentiation and similar levels of genetic diversity to the surrounding natural stands were found for nuclear markers. However, chloroplast microsatellites presented lower haplotype diversity in reforested stands, and this may be a consequence of the lower effective population size of the chloroplast genome, meaning chloroplast markers have a higher sensitivity to bottlenecks. Understory natural regeneration within the reforestation was also analysed to study gene flow from natural forest into artificial stands. Estimates of immigration rate into artificially regenerated forest were high (0.68-0.75), producing a significant increase of genetic diversity (both in chloroplast and nuclear microsatellites), which indicates the capacity for genetic recovery for P. canariensis reforestations surrounded by larger natural stands.