Final answer:
The term referring to the varying behavior of Daphnia in the presence or absence of preadatory fish, which demonstrates the dynamic relationship between genotype and environment, is 'genotype-by-environment interaction'. This concept is key in understanding population dynamics and predicting ecological outcomes.
Step-by-step explanation:
The variation in response observed by Luc De Meester in Daphnia genotypes that altered their behavior in the presence versus absence of predatory fish is termed genotype-by-environment interaction. This term explains how different genotypes respond to environmental challenges in unique ways. The study, which involves measuring changes in phototactic behavior, shows that the behaviors of Daphnia can change based on the genotypic characteristics in response to the number of predatory fish in their environment.
Genetic variability in the original population is demonstrated by the presence of multiple responses to the same environmental pressure, indicating that there are different alleles influencing the trait within the population. Furthermore, the reciprocal effects of the environment and the evolution of populations highlighted in the study emphasize the complexity involved in the interactions between organisms and their environments. This dynamic relationship is essential to understanding population dynamics and can be used to inform simulation models that predict ecological outcomes.