Seed dormancy varies widely among Arabidopsis thaliana populations both between and within Fennoscandia and Italy

Abstract

The timing of germination is a key life‐history trait in plants, which is strongly affected by the strength of seed dormancy. Continental‐wide genetic variation in seed dormancy has been related to differences in climate and the timing of conditions suitable for seedling establishment. However, for predictions of adaptive potential and consequences of climatic change, information is needed regarding the extent to which seed dormancy varies within climatic regions and the factors driving such variation. We quantified dormancy of seeds produced by 17 Italian and 28 Fennoscandian populations of Arabidopsis thaliana when grown in the greenhouse and at two field sites in Italy and Sweden. To identify possible drivers of among‐population variation in seed dormancy, we examined the relationship between seed dormancy and climate at the site of population origin, and between seed dormancy and flowering time. Seed dormancy was on average stronger in the Italian compared to the Fennoscandian populations, but also varied widely within both regions. Estimates of seed dormancy in the three maternal environments were positively correlated. Among Fennoscandian populations, seed dormancy tended to increase with increasing summer temperature and decreasing precipitation at the site of population origin. In the smaller sample of Italian populations, no significant association was detected between mean seed dormancy and climate at the site of origin. The correlation between population mean seed dormancy and flowering time was weak and not statistically significant within regions. The correlation between seed dormancy and climatic factors in Fennoscandia suggests that at least some of the among‐population variation is adaptive and that climate change will affect selection on this trait. The weak correlation between population mean seed dormancy and flowering time indicates that the two traits can evolve independently.

Effects of primary seed dormancy on lifetime fitness of Arabidopsis thaliana in the field

“…4B , D , F ). Previous work at the study site has shown that the Italian and Swedish genotypes differ in their annual seed dormancy cycle, with the Swedish genotype releasing its seed dormancy earlier compared to the Italian genotype ( Postma et al , 2016 ; Zacchello, 2021 ), and that this is associated with earlier germination ( Postma and Ågren, 2018 ; see also Fig. 2A ).…”

“…Interestingly, by the end of the germination period in the 2013 experiment, the mean proportion of seeds that had germinated in the RIL population was higher than that of the two parental genotypes. The Italian and Swedish genotypes differ in the timing of their annual seed dormancy cycles ( Postma et al , 2016 ; Zacchello, 2021 ), and the among-year variation in germination proportion of different genotypes may reflect differences in the match between the timing of dormancy release and seasonal changes in conditions for germination, as suggested by the conceptual model illustrated in Fig. 4B , D and F .…”

“…We have not included potential recruitment from the seed bank in our fitness estimates, but the secondary dormancy cycles observed in previous seed burial experiments at the field site suggest that potential recruitment from the seed bank would increase the advantage of the local genotype ( Postma et al , 2016 ; Zacchello, 2021 ).…”

Climate biogeography of Arabidopsis thaliana: Linking distribution models and individual variation

“…We developed a set of high‐quality occurrence data (i.e. species ID verified and location checked, N = 4024) from published research (Durvasula et al, 2017; Hsu et al, 2019; Mandáková et al, 2017; Zacchello et al, 2022; Zeng et al, 2017; Zou et al, 2017), publicly available herbarium and germplasm accessions with known collection locations (Alonso‐Blanco et al, 2016; DeLeo et al, 2020), and some of our recent field collections in East Africa (Gamba et al, 2022). These span a period of 1794–2018.…”

Ascorbic acid releases dormancy and promotes germination by an integrated regulation of abscisic acid and gibberellin in Pyrus betulifolia seeds

“…Seed dormancy is an adaptive trait that evolved to enhance seedling survival by avoiding germination under unsuitable environmental conditions (Liu et al 2019a; Iwasaki et al 2022). Dormancy varies between species, clades, communities, and regions and is regulated by both internal and external factors (Zacchello et al 2022; Pausas and Lamont 2022). That is, dormancy results from genetic and environmental factors and their interactions.…”