Genetic diversity matters for restoration of a threatened saltmarsh plant in harsh environments

While genetic diversity is theorised to increase the restoration success
of degraded plant populations, previous studies examining its impacts on
restoration outcomes have yielded mixed results. We hypothesise that the
importance of genetic diversity for the performance of plants targeted for
restoration increases with environmental stress and varies with specific
plant traits related to different plant successive life stages. To test
this, we conducted a fully factorial common garden experiment, crossing
salinity and genetic diversity under low- and high-nitrogen conditions on
the growth and reproduction of Scirpus mariqueter, a threatened endemic
saltmarsh plant in the Yangtze Estuary. The impacts of genetic diversity
varied across stress gradients and metrics. Under high stress (high
salinity, low nutrients), greater diversity enhanced reproductive traits
such as clonal growth and seed production, but not under low stress. Plant
growth traits showed no diversity effects regardless of stress. Synthesis.
Our results highlight the importance of considering intraspecific genetic
diversity in ecological restoration and help explain the context-dependent
effects of diversity.