Impacts of ecological restoration on the genetic diversity of plant species: a global meta-analysis.
In contrast to the depth of knowledge available for the enhancement of plant species diversity and ecosystem services through ecological restoration, our understanding of how ecological restoration impacts genetic diversity (GD) of plant species has not yet been synthesized. We performed a global meta-analysis to examine whether ecological restoration improved GD of plant species in restored populations. First, we compared the GD of restored populations with reference or degraded populations. Second, we explored whether the influence of ecological restoration on plant GD varies between species with different characteristics (life form and threat status), between different restoration strategies (active/passive, seeding/planting, mixture/non-mixture) or between different restoration times (<50 and = 50 years; with an average of 29.3 years). The GD of restored populations was significantly lower (HE, 1.06%; PPB, 5.10%, and SWI, 4.95%) than in reference populations but was comparable to degraded populations. The inbreeding coefficient (FIS, the proportion by which the heterozygosity of an individual is reduced by inbreeding) was consistently comparable between restored populations and reference or degraded populations. Woody species but not herbs and forest but not grassland ecosystem had significantly lower GD in restored populations than in reference populations. Passive but not active restoration, seeding rather than planting, and mixing materials from different sources rather than using a single source, all significantly increased the GD of restored populations. When the restoration time was =50 years, in contrast to <50 years, GD was comparable between the restored and reference populations. Synthesis and applications. In general, ecological restoration did not significantly improve the GD of plant species compared to reference or degraded populations. This might be due in part to the relatively short restoration time. Using passive restoration, seeding, and mixed sources could significantly increase the GD of restored populations. We emphasize that GD should not be treated as a minor cobenefit of ecological restoration for other purposes and that the recovery of GD should be listed as a vital goal in future ecological restoration with plant species.