Investigation into Adaptation in Genes Associated with Response to Estrogenic Pollution in Populations of Roach (Rutilus rutilus) Living in English Rivers

Exposure
of male fish to estrogenic substances from wastewater
treatment works (WwTWs) results in feminization and reduced reproductive
fitness. Nevertheless, self-sustaining populations of roach (Rutilus rutilus) inhabit river stretches polluted
with estrogenic WwTW effluents. In this study, we examine whether
such roach populations have evolved adaptations to tolerate estrogenic
pollution by comparing frequency differences in single-nucleotide
polymorphisms (SNPs) between populations sampled from rivers receiving
either high- or low-level WwTW discharges. SNPs within 36 “candidate”
genes, selected for their involvement in estrogenic responses, and
120 SNPs in reference genes were genotyped in 465 roaches. There was
no evidence for selection in highly estrogen-dependent candidate genes,
including those for the estrogen receptors, aromatases, and vitellogenins.
The androgen receptor (ar) and cytochrome P450 1A
genes were associated with large shifts in allele frequencies between
catchments and in individual populations, but there is no clear link
to estrogen pollution. Selection at ar in the effluent-dominated
River Lee may have resulted from historical contamination with endocrine-disrupting
pesticides. Critically, although our results suggest population-specific
selection including at genes related to endocrine disruption, there
was no strong evidence that the selection resulted from exposure to
estrogen pollution.