Effects of genetic diversity on conservation and restoration potential at individual, population, and regional scales

- We studied the effects of genetic diversity at three scales for Vallisneria americana.
- Heterozygosity increased turion biomass and leaf area at the individual scale.
- More genotypes enhanced ramet production and flowering at the population scale.
- Opportunities for selection differed among source beds at the regional scale.
- Effective conservation and restoration requires assessment of genetic diversity at all three scales.

All available evidence suggests that genetic diversity is important for ecological performance and resilience through the expression and variance of phenotypic traits. Genetic diversity is a multiscalar variable; it includes heterozygosity at the individual scale, genotypic diversity at the population scale, and local adaptation at the regional scale. The three scales of genetic diversity are predominantly studied in isolation to determine conservation status or restoration potential. However, synergisms among the three scales should enhance conservation and restoration assessments. We studied 49 genotypes of Vallisneria americana, a common freshwater submersed aquatic macrophyte that has seen catastrophic declines in its estuarine habitats. Two greenhouse experiments examined phenotypic traits and trade-offs and the effects of genetic diversity on the sustainability of V. americana populations. Clone size, an exploitative guerilla strategy, and plant height, a conservative phalanx strategy, were negatively associated, as were average turion size with clone size and turion abundance, suggesting that growth strategies trade-off to affect plant fitness. Leaf size and turion size were lower in individuals with lower heterozygosity. Early clonal expansion and flowering frequency were enhanced when genotypic richness was higher. Coefficients of variation revealed that opportunities for selection differed across V. americana source beds. We demonstrate that the three scales of genetic diversity work together to determine population performance and evolutionary potential. Thus, integrating the three aspects of genetic diversity is paramount in addressing the impacts of a changing world on the conservation and restoration potential of at-risk populations.