Carry-Over
Effects Across Metamorphosis of a Pesticide
on Female Lifetime Fitness Strongly Depend on Egg Hatching Phenology:
A Longitudinal Study under Seminatural Conditions
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Abstract
Current
ecological risk assessment of pesticides fails to protect
aquatic biodiversity. For the first time, we tested two potential
reasons for this failure with regard to carry-over effects across
metamorphosis: their dependence on hatching period, and the lack of
studies quantifying adult fitness under seminatural conditions. Using
the damselfly <i>Coenagrion puella</i> sampled from six
populations, we designed an outdoor longitudinal one-year study starting
from the egg stage. We exposed the aquatic larvae to the pesticide
esfenvalerate (0.11 μg/L) during the initial microcosm part.
Next, we monitored the lifetime fitness of the terrestrial adults
in an insectary. Exposure to the pesticide negatively impacted not
only larval traits, but also drastically reduced lifetime mating success
of adult females. The impact of this postmetamorphic effect of the
pesticide on the population level was three times more important than
the effects in the larval stage. Importantly, this carry-over effect
was only present in females that hatched early in the season, and
was not mediated by metamorphic traits (age and mass at emergence).
We provide proof-of-principle under seminatural conditions for two
potential pitfalls that need to be considered when improving risk
assessment: carry-over effects on adult fitness can (i) be much more
important than effects during the larval stage and may not be captured
by metamorphic traits, and (ii) be strongly modulated by egg hatching
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