Trait divergence along the rainfall gradient
Eight traits showed significant clinal trends across the natural
rainfall gradient, suggesting an adaptive role for these traits with
rainfall. Towards drier sites,
plants decreased in germination fraction, days to flowering, stomata
density, height, and biomass, and they increased in reproductive
allocation and seed production (Table 2, Fig. 1). Furthermore, flowering
started at smaller plant size (fewer leaves) in drier sites, although at
MM, plants invested less in lateral branches and thus possessed fewer
but larger leaves along the main stem (Petrů et al . 2006; pers.
obs.). There was a marginally significant tendency towards lowerδ 13C in arid sites (p=0.08, Fig. 1) and no
clinal trend for diaspore weight despite significant differences among
sites (Table 2, Fig. 1).
The clinal trends across sites in flowering time, leaf number at
flowering and reproductive allocation matched the direction of their
rapid evolutionary response within ten years climate manipulation. In
contrast, five traits showed clines along the natural rainfall gradient
but no rapid evolution under climate manipulations (germination
fraction, stomata density, height, biomass, seed number).
The five water levels in the greenhouse affected all traits (Table 1 &
2; Fig. S1 supp. information), indicating plasticity in response to
water. Clearly significant site × water interactions for all traits
except reproductive allocation (p=0.08) indicated genetic variation in
trait plasticity among sites (Table 2).