Morphological integration, canalization, and plasticity in response to emergence time in Abutilon theophrasti

The relationships between trait plasticity and canalization, and between
phenotypic integration and plasticity, have been under debate, largely
because direct evidence is still scarce for their associations, especially
in response to environments. To investigate the relationships between
canalization, integration, and phenotypic plasticity in response to
emergence time, we conducted a field experiment with an annual herbaceous
species of Abutilon theophrasti, by subjecting plants to four treatments
of emergence time (spring, late spring, summer, and late summer), to
measure several morphological traits and analyze correlations of
plasticity with canalization and integration in these traits, at two
stages of plant growth. Results showed plants with delayed emergence had
higher phenotypic integration and more positive correlations between
integration and plasticity, but less negative correlations between
decreased canalization and plasticity, compared to those that emerged in
spring. Results suggested significant environmental changes that induce
plastic responses, rather than environmental stress, can result in greater
phenotypic integration in plants. Negative correlations between decreased
canalization and plasticity occurred more frequently in plants emerging in
spring and the least frequently in those emerging in summer, suggesting
their relationship depends on specific environmental conditions and the
degree of plasticity. Both increased phenotypic integration and decreased
canalization might merely be the outcome of plastic responses, rather than
mechanisms constraining or facilitating plasticity.