Estrogen, shrubbery, and the sex ratio of suburban frogs

[KamaAina]

http://news.yale.edu/2015/09/08/estrogen-shrubbery-and-sex-ratio-suburban-frogs

Green frogs in the suburbs are seeing a gender revolution.

A new Yale study shows that estrogen in suburban yards is changing the ratio of male and female green frogs at nearby ponds. Higher levels of estrogen in areas where there are shrubs, vegetable gardens, and manicured lawns are disrupting frogs’ endocrine systems, according to the study. That, in turn, is driving up the number of female frogs and lowering the number of male frogs....

Previous studies have shown similar effects caused by agricultural pesticides and wastewater effluent; the new study finds amphibian endocrine disruption also exists in suburban locales.

“In suburban ponds, the proportion of females born was almost twice that of frog populations in forested ponds,” said lead author Max Lambert, a doctoral student at the Yale School of Forestry & Environmental Studies. “The fact that we saw such clear evidence was astonishing.”

[Solly Mack]

1. K&R

[enough]

2. Link to the original article:

http://www.pnas.org/content/early/2015/09/02/1501065112.abstract?sid=300185c9-c20f-4d81-8c91-f309ba01dfb2

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.