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Strong stabilizing selection on timing of germination in a Mediterranean population of Arabidopsis thaliana

Citation

Zacchello, Giulia; Vinyeta, Mariona; Ågren, Jon (2021), Strong stabilizing selection on timing of germination in a Mediterranean population of Arabidopsis thaliana, Dryad, Dataset, https://doi.org/10.5061/dryad.5qfttdz2m

Abstract

Premise

Timing of germination can strongly influence plant fitness by affecting seedling survival and by having cascading effects on later life-history traits. In seasonal environments, the period favorable for seedling establishment and growth is limited, and timing of germination is likely to be under stabilizing selection because of conflicting selection through survival and fecundity. Moreover, optimal germination time may vary among genotypes because of inherent differences in later life-history traits.

 

Methods

To examine how germination time affects survival, fecundity and the relative fitness of two genotypes differing in time to first flower, we conducted a field experiment in an Italian population of the winter annual Arabidopsis thaliana, in which seedling establishment occurs mainly in November. We transplanted seedlings of the local genotype and of a Swedish genotype monthly from August to December and monitored survival and fecundity.

 

Key Results

Only seedlings transplanted in November and December survived until reproduction, and fitness of the November cohort was 35 times higher than that of the December cohort, indicating strong stabilizing selection. There was no evidence of conflicting selection: seedling survival, adult survival and fecundity were all highest in the November cohort. Moreover, the relative fitness of the two genotypes did not differ significantly between cohorts.

 

Conclusions

The very narrow window of opportunity for seedling establishment was related to rapid seasonal changes in soil moisture and temperature, suggesting that rate of seasonal change is an important aspect to consider for understanding spatio-temporal variation in selection on phenological traits.