3. Categorized factors associated with variations in inducible
defense
We identified seven secondary factors causing variations in inducible
defense based on previous studies (Fig. 1); abiotic factors, ecological
and evolutionary traps, food, alarm substance, clone/genotypes, instars,
and maternal effect. The following three factors were not noted owing to
the paucity of prior research or controversy: abiotic factor, ecological
trap, and alarm cue (Fig. 1).
The seven factors can be distinguished by their relative relationship to
primary factors (Fig. 2). One is the primary factors to promote or
inhibit the degree of expression in inducible defense by working with
the primary factors; abiotic factors, food, clone/genotype, and instars.
The other is the secondary factor alone can express predator-induced
plasticity, but the degree of expression may be equivalent, smaller or
larger compared with the induction traits from the primary factor;
abiotic factors, ecological evolutional traps, alarm substance, and
maternal effect. If organisms can express an inducible defense with as
few factors as possible, it would be adaptive to take less cost than to
perceive a number of factors. To the cost of factor acquisition (DeWitt
et al. 1998), organisms would try to assess environment to express
phenotype-environment matching. Given the avoidance of mismatching
phenotypes, secondary factor may help the control, accelerate, and limit
of the expression of defensive plasticity, in addition to ensuring the
reliability of primary factors.