title: Suburbanization, estrogen contamination, and sex ratio in wild amphibian populations.
abstract: Research on endocrine disruption in frog populations, such as shifts in sex ratios and feminization of males, has predominantly focused on agricultural pesticides. Recent evidence suggests that suburban landscapes harbor amphibian populations exhibiting similar levels of endocrine disruption; however the endocrine disrupting chemical (EDC) sources are unknown. Here, we show that sex ratios of metamorphosing frogs become increasingly female-dominated along a suburbanization gradient. We further show that suburban ponds are frequently contaminated by the classical estrogen estrone and a variety of EDCs produced by plants (phytoestrogens), and that the diversity of organic EDCs is correlated with the extent of developed land use and cultivated lawn and gardens around a pond. Our work also raises the possibility that trace-element contamination associated with human land use around suburban ponds may be contributing to the estrogenic load within suburban freshwaters and constitutes another source of estrogenic exposure for wildlife. These data suggest novel, unexplored pathways of EDC contamination in human-altered environments. In particular, we propose that vegetation changes associated with suburban neighborhoods (e.g., from forests to lawns and ornamental plants) increase the distribution of phytoestrogens in surface waters. The result of frog sex ratios varying as a function of human land use implicates a role for environmental modulation of sexual differentiation in amphibians, which are assumed to only have genetic sex determination. Overall, we show that endocrine disruption is widespread in suburban frog populations and that the causes are likely diverse.
authors.affiliation: School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511; max.lambert@yale.edu.
authors.forename: Max R
authors.initials: MR
authors.lastname: Lambert
authors.affiliation: School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511;
authors.forename: Geoffrey S J
authors.initials: GS
authors.lastname: Giller
authors.affiliation: U.S. Geological Survey, Boulder, CO 80303.
authors.forename: Larry B
authors.initials: LB
authors.lastname: Barber
authors.affiliation: U.S. Geological Survey, Boulder, CO 80303.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: Fitzgerald
authors.affiliation: School of Forestry and Environmental Studies, Yale University, New Haven, CT 06511;
authors.forename: David K
authors.initials: DK
authors.lastname: Skelly
mesh_terms: D000663:Amphibians / Q000502:physiology*; D000818:Animals; D000835:Animals, Wild / Q000502:physiology*; D003237:Connecticut; D052244:Endocrine Disruptors / Q000032:analysis; D004967:Estrogens / Q000032:analysis*; D005260:Female; D065928:Forests; D006801:Humans; D008297:Male; D008675:Metamorphosis, Biological; D061005:Ponds; D011898:Ranidae / Q000502:physiology; D012744:Sex Ratio; D013383:Suburban Population; D014874:Water Pollutants, Chemical / Q000032:analysis
chemical_list: D052244:Endocrine Disruptors; D004967:Estrogens; D014874:Water Pollutants, Chemical
keywords: environmental sex determination; estrone; landscaping; lawn; phytoestrogen