WONG, THEODORE G. Dept. of Biological Science, Florida State Univ., Tallahassee, FL 32306. - Architectural integration of traits and plasticity in simulated plants.
A plant's program of architectural development can be a powerful
driver of phenotypic integration, and architectural plasticity an
important mechanism behind integrated trait responses. In order to
assess architecture's contribution to overall trait integration, I
simulated architectural growth computationally using several realistic
models consisting of combinations of branching, elongation, and
meristem-identity rules. Architectural plasticity was embodied in the
rules themselves and was expressed as the architectural response to
simple simulated environmental variables. In contrast to many
plant-growth simulations, mine was based exclusively on individual
metamer behavior: architectures, trait correlations, and trait
reponses all emerged from the iterated application of rules to each
metamer of the simulated plant in each time-step of the simulation.
The architectural program's contribution to trait and plasticity
integration was assessed by changing rule parameters and observing
changes in traits, their correlations, their plastic responses, and
the correlations among the responses. Architecture was responsible for
strong correlations among many architectural and life-history traits,
correlations which persisted across environmental conditions but which
differed when rule parameters or the rules themselves were changed.
The rules with the greatest integrating effect were those that defined
the control of flowering. Rules that defined branching frequency or
the duration of meristem viability had relatively little integrating
effect. That architecture should play a large role in trait and
plasticity integration is unsurprising given the importance of other
types of developmental linkage. That architectural rules differ in
their effect suggests that the dissection of architecture is an
important early step in the study of architecture's evolutionary and
ecological consequences. Given how straightforwardly the architectural
program can be described computationally, simulation should prove to
be a useful tool both in the definition of architectural models and in
the elucidation of their importance.
Key words: architecture, development, phenotypic integration, phenotypic plasticity, simulation, trait correlations