Consequences of 3,4-dichloroaniline to guppy populations ( Poecilia reticulata): computer simulation and experimental validation

In order to evaluate the effects of 3,4-dichloroaniline (3,4-DCA), which were detected in a life-cycle test with guppies, on the population level, laboratory guppy populations were examined with regard to regulative parameters. Among the endpoints investigated in life-cycle tests, fecundity was shown to be a sensitive parameter. In laboratory guppy populations, however, intraspecific predation on newborn was the main regulator. Based on these data, a computer simulation programme was used to predict the consequences of 3,4-DCA to guppy populations. A population exposure experiment was conducted to validate the simulation results. The effects detected in the life-cycle test (LOEC: 2 μg/1) were compensated for on the population level; no significant reduction of mean abundance could be stated. The mean population effect was well predicted by the simulation, but the variance was much higher in the exposure experiment: individual differences of the sensitivity of fecundity towards stress caused by xenobiotics and density were not modelled adequately. The loss of genetic diversity and, as follows, the deterioration of the adaptive potential of the species by xenobiotic effects can easily be overseen, when looking at common life-cycle test endpoints only.