Introduction - Ecological Biomarkers: Indicators of Ecotoxicological Effects - page 8

to the population level have been reviewed (Maltby et al. 2001). Among those, dynamic
energy budget models combined with demographic models have been well developed
(Charles et al. 2009).
Exposure to chemicals can lead to DNA damage (Figure 1.5), the consequences of which
may be limited by DNA repair (Peterson and Côté 2004). Mutations frequently have toxic
effects, including carcinogenesis, and when affecting germinal tissues, they are inherit-
able and can also affect future generations, provided that the offspring are viable and able
to survive and reproduce. In fact, impairments of germinal cells often result in embryo
lethality or early death of the progeny. From an ecological point of view, it is questionable
if these precocious deaths can impact the fate of populations (Manahan 2003; Newman
and Clements 2008). In some cases, mutations can confer a selective advantage leading to
the selection of resistant genotypes. Biomarkers of exposure to genotoxic pollutants are
reviewed in Chapter 13, and Vasseur et al. explore the relationships between genotoxicity
and population effects.
Chronic exposure to chemicals can exert a selection pressure leading to the presence
of resistant genotypes in organisms living in impacted areas. The acquisition of toler-
ance is particularly well documented for pesticide-exposed insects (Hemingway et al.
2004), but other classes of contaminants (metals, PAHs, PCBs) can be responsible for the
predominance of resistant genetic patterns in bacteria (Nies 1999), plants (Frérot et al. in
Amiard-Triquet et al. 2011), invertebrates (Nevo et al. 1984), and vertebrates (Athrey et al.

Exposure to chemicals

DNA Damage

Selection of resistant genotypes

- DNA adducts
- Chromosomal aberrations
- Aneuploidy or polyploidy

Genetic
diversity

Metabolic cost

Maintainance of DNA integrity
Duplication of specific genes

Fitness
(fecundity, condition,
growth rate, etc.)

DNA Repair
Compensation at
population level

Adaptability
to new environments

Probability
of local extinction

Balance?

Survival in polluted
ecosystems

Ecological consequences?

FIGURE 1.5
Genetic responses to chemical exposure: DNA damage versus selection of resistant genotypes.