Seed dormancy vs. climate at site of origin
Factor loadings of climatic variables on PCs are shown in Table
3 and Figure S4 . Within Fennoscandia, mean temperature of the
warmest month and of the warmest quarter decreased with PC1, while mean
annual precipitation and mean precipitation during the warmest quarter
increased with PC1. Annual temperature was instead negatively associated
with PC2. For seeds produced by Fennoscandian populations in the
greenhouse, germination proportions quantified 1 and 3 weeks after seed
maturation tended to increase with PC1 (germination proportion 1 week:
partial linear regression coefficient, β = 0.0387, P = 0.033;
germination proportion 3 weeks: β = 0.0799, P = 0.003, Table
4 ), whereas no association was found with PC2 or PC3. Seed dormancy
thus tended to be stronger in populations from sites with relatively
high summer temperature and low precipitation than in populations
originating from sites with low summer temperature and high
precipitation.
Within Italy, temperature variables increased with PC1, and
precipitation variables increased with PC2 (Table 3 ). Mean
annual precipitation was positively associated with PC3, while mean
precipitation during the warmest quarter showed an opposite trend
(Table 3 ). Germination proportions of seeds produced by Italian
populations in the greenhouse were very low 1 and 3 weeks after seed
maturation (Fig. 3A ) and were not significantly associated with
any PC.
No significant association was found between PCs and germination
proportions of seeds 12 weeks after harvest in the greenhouse or in the
field (Table 4 ), and mean germination proportions did not vary
with latitude or longitude of origin in either region
(P>0.05, not shown).