The effect of region of origin and maternal environment on
dormancy level
Seeds produced by Italian populations had on average stronger seed
dormancy 12 weeks after seed maturation than had seeds produced by
Fennoscandian populations both at the Italian field site and in the
greenhouse (F1,41 = 69.7, p < 0.001,Fig. 3A and Table 1 ). At the Swedish field site, very
few Italian populations managed to produce sufficient amounts of seeds
to allow germination tests. However, the few lines tested tended to
produce seeds with stronger dormancy compared to the seeds produced by
Fennoscandian populations also at that site (Fig. 3A andTable 1 ).
Germination proportions were on average 37% higher among seeds matured
at the Italian field site compared to those matured in the greenhouse
(F1,331 = 15.4, p < 0.001), and this effect
did not vary with region of origin (region of origin × maternal
environment interaction, F1,331 = 1.2, p = 0.27;Fig. 3A and Table 1 ). Germination proportions varied
among populations within regions (L-ratio6,7 = 107.5, p
< 0.001, Fig. 3A and Table 1 ). Although
germination proportions 12 wk after seed maturation in each of the three
maternal environments were positively correlated (Spearman rank
correlation, Italy field vs. Sweden field, rs = 0.63, N
= 30, p < 0.001; Italy field vs. Greenhouse,
rs = 0.52, N = 43, p < 0.001; Sweden field vs.
Greenhouse, rs = 0.88, N = 32, p < 0.001), the
effect of population differed between the two maternal environments
(significant population × maternal environment interaction,
L-ratio7,9 = 158.8, p < 0.001, Fig.
3A and Table 1 ). The interaction reflected the fact that
variance in germination proportion among Fennoscandian populations 12
weeks after seed maturation was much larger when seeds had been produced
in the greenhouse compared to when matured at the Italian site, whereas
for Italian populations the opposite was true (Fig. 3A ). For
both regions of origin, the highest variance in population means was
observed when the overall mean germination proportion was intermediate
(seeds of Fennoscandian populations grown in the greenhouse, and of
Italian populations grown at the Italian field site) rather than very
high (Fennoscandian populations at the Italian field site) or very low
(seeds of Italian populations in the greenhouse; Fig. 3A ). The
seeds of all populations except one (Ørnes, the northernmost sampled
population from Fennoscandia) had higher germination proportions when
matured in Italy compared to in the greenhouse. Removal of this
population from the dataset did not affect the significance of the
population × maternal environment interaction (not shown).
Germination proportions of seeds
produced at the two field sites varied among Fennoscandian populations
(F17,113 = 11.3, p < 0.001, Fig. 3Aand Table 2 ), and the variance among populations was markedly
larger for seeds produced at the Swedish field site compared to seeds
produced at the Italian field site (maternal environment x population
interaction, F17,113 = 5.4, p < 0.001,Fig. 3A and Table 2 ).
Among seeds matured in the greenhouse, Fennoscandian populations had on
average higher germination proportions than had Italian populations in
all tests conducted during one year of after-ripening. The average
germination proportion of Fennoscandian populations increased from about
10% one week after seed harvest to 50% eleven weeks later, and reached
a maximum of about 75% after one year of after-ripening (Fig.
3B ). By contrast, the average germination proportion of Italian
populations was below 17% during the first 12 weeks of after-ripening,
and reached 50% only after one year (Fig. 3B ). Still after 54
weeks of after-ripening, germination proportion varied widely among both
Fennoscandian and Italian populations (Fig. 3B ).