Clover root exudate produces male-biased sex ratios and accelerates male metamorphic timing in wood frogs.

Max R Lambert

doi:10.1098/rsos.150433

Abstract

In amphibians, abnormal metamorph sex ratios and sexual development have almost exclusively been considered in response to synthetic compounds like pesticides or pharmaceuticals. However, endocrine-active plant chemicals (i.e. phytoestrogens) are commonly found in agricultural and urban waterways hosting frog populations with deviant sexual development. Yet the effects of these compounds on amphibian development remain predominantly unexplored. Legumes, like clover, are common in agricultural fields and urban yards and exude phytoestrogen mixtures from their roots. These root exudates serve important ecological functions and may also be a source of phytoestrogens in waterways. I show that clover root exudate produces male-biased sex ratios and accelerates male metamorphosis relative to females in low and intermediate doses of root exudate. My results indicate that root exudates are a potential source of contaminants impacting vertebrate development and that humans may be cultivating sexual abnormalities in wildlife by actively managing certain plant species.

Highlights

Human activities like agriculture and suburbanization are associated with altered frog sex ratios at metamorphosis [1,2]
Analyses of individual phytoestrogens indicate that phytoestrogens readily impact hormone pathways important in vertebrate sexual development [8]
I test whether root exudate impacts metamorphosing frog sex ratios and somatic developmental rates

Summary

Introduction

Human activities like agriculture and suburbanization are associated with altered frog sex ratios at metamorphosis [1,2]. Sex ratio biases and other sexual abnormalities are hypothesized to be due to pesticides, pharmaceuticals, or other wastewater contaminant exposure [3,4,5,6,7]. With a focus on synthetic chemicals, minimal attention has been given. 2 (ii) to natural chemicals, such as phytoestrogens produced by plants. Analyses of individual phytoestrogens indicate that phytoestrogens readily impact hormone pathways important in vertebrate sexual development [8]. We know little about how phytoestrogens enter waterways or what the biological effects of relevant phytoestrogen mixtures are [9]

Methods

Results

Conclusion