Developmental canalization
Theoretically, it is predicted increments in environmental variations
may lead to relatively higher levels of plasticity in morphological
traits (Bradshaw, 1965;
de Jong, 1995), whereas fitness-traits may
be more likely to maintain stable under a range of environmental
conditions (Lerner, 1954;
Stearns & Kawecki, 1994;
Waddington, 1957;
Wagner et al., 1997). Characters more
closely related to fitness are expected to be better buffered against
environmental effects because deviations from the optimal phenotype will
be strongly selected against (Clarke,
1995; Lerner, 1954;
Stearns & Kawecki, 1994;
Waddington, 1957). These predictions have
been proved by the contrasting performances in the degree of plasticity
in response to temperature between morphological traits and fitness
traits (Liefting et al. , 2009).
However, we did not find reproductive mass ratio had lower plasticity in
response to density than other traits, and its among-individual
variation (CV) was higher than other traits at different densities,
consistent with other studies (Woodset al. , 1999). It suggested the relative stability of fitness
traits depends on the level or range of environmental variations, and
increased phenotypic variations can be produced under highly stressful
conditions that plants are incapable to adapt
(Woods et al. , 1999). When the
stress is severe enough, the buffering against drastic changes may no
longer be able to prevent such overt changes, and phenotypic variability
in more robust traits might assist survival at the population level
(Elgart et al. , 2015). The
increase of density should have been severe enough to cause the decrease
of reproductive allocation in this study.