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Eight generations of native seed cultivation reduces plant fitness relative to the wild progenitor population

Citation

Pizza, Riley; Espeland, Erin; Etterson, Julie (2021), Eight generations of native seed cultivation reduces plant fitness relative to the wild progenitor population, Dryad, Dataset, https://doi.org/10.5061/dryad.1c59zw3v8

Abstract

Native seed for restoration is in high demand, but widespread habitat degradation will likely prevent enough seed from being sustainably harvested from wild populations to meet this need. While propagation of native species has emerged in recent decades to address this resource gap, few studies have tested whether the processes of sampling from wild populations, followed by generations of farm cultivation, reduces plant fitness tolerance to stress over time. To test this, we grew the eighth generation of farm-propagated Clarkia pulchella Pursh (Onagraceae) alongside seeds from two of the three original wild source populations that established the native seed farm. To detect differences in stress tolerance, half of the plants were subjected to a low-water treatment in the greenhouse. At the outset, farmed seeds were 4.1% heavier and had 4% greater germination compared to wild-collected seed. At maturity, farmed plants were 22% taller and had 20% larger stigmatic surfaces, even after accounting for differences in initial seed size. Importantly, the mortality of farmed plants was extremely high (75%), especially in the low-water treatment (80%). Moreover, farmed plants under the high-water treatment had 90% lower relative fitness than wild plants due to the 1.3 times greater weekly mortality and a 3-fold reduction in flowering likelihood. Together, these data suggest that bottlenecks during initial sampling and/or unconscious selection during propagation severely reduced genetic diversity and promoted inbreeding. This may undermine restoration success, especially under stressful conditions. These results indicate that more data must be collected on the effects of cultivation to determine whether it is a suitable source of restoration seed.

Methods

Data were collected on 1500 wild and farmed (750 from each seed source) Clarkia pulchella plants grown in the greenhouse at the University of Minnesota Duluth. All data were analyzed in JMP except Aster.csv, which was analysed in R using the statistical package "aster".

Usage Notes

See readme file for details on each of the files.

Funding

Garden Club of America, Award: Ecological Restoration Fellowship

Sigma Xi, Award: Grant-in-aid-of-research