|
Jon P. Nash
Katolike Universiteit Leuven,
Belgium
Title
The mating system is a pivotal factor
in determining the population level consequences of endocrine disruption
Abstract
There is strong evidence that exposure to endocrine
disrupting chemicals is causing significant disruption to the normal function
of the reproductive system of many species of wildlife. It is vitally
important to determine the population consequences of this impaired
reproductive function. We suggest that the mating system is a key factor in
determining the population level consequences of endocrine disruption. The
most important population-level consequences of reproductive dysfunction will
be: 1) lowered reproductive success when the number and/or viability of the
offspring is reduced, and 2) changes to the genetic structure of the population
when gene flow is altered. The processes that determine the successful
production of viable offspring and maintenance of genetic heterogeneity in a
population are complex, and understanding the impact of impaired reproductive
function on these processes is not straight forward. Even when the number of
female gametes is unaffected, their viability may be reduced if there is
significant reduction in male fertility. The degree to which reduced male
fertility, or even infertility in some individual males, affects
fertilisation success will be highly dependent on the mating system of the
species. When there is a pair-wise mating, for example, then the vitality of
the male may have a strong impact on fertilisation success. Moreover, if
males with lowered fertility were equally able to compete against
reproductively healthy males for access to females, the population level
impact of decreased fertility could be far greater. This would mean that a
higher threshold of sensitivity to behavioural disruption compared with that
which causes reduced fertility, may in fact produce stronger population level
consequences. Conversely, when multiple males fertilise the eggs, the lowered
vitality of particular males may have a lesser impact on fertilisation
success. They may, however, still strongly affect gene flow, thus impacting
on the genetic integrity of the population. Moreover, there exists the
possibility of other important interactions between endocrine disruption and
mating systems that could strongly influence the population level impact of
reduced fertility. Sexual selection and mate choice strategies are complex
and endocrine disruption may interact or interfere with these in both
negative and positive ways. For example, the factors that determine the
choice of a male by the female could be exaggerated in males with reduced
fertility, giving these fish an even greater potential for interfering with
the natural mating process and further increasing the impact of endocrine
disruption on reproductive success. In this paper we present experimental
data on populations of zebrafish with good evidence
that the character of the mating system is a key factor in determining the
population level impact of endocrine disruption. We will discuss these data
and how greater knowledge of mating systems will help in understanding and
predicting the environmental impacts of endocrine disruption in
wildlife.
Poster (pdf, 0.9MB)
Laboratory of Aquatic Ecology
Katholieke Universiteit Leuven
Charles de Bériotstraat 32
B-3000 Leuven
Belgium
http://www.kuleuven.ac.be/bio/eco
|
