Seddon, E. | bioRxiv Science

bioRxiv2021

Herbivory enhances leaky sex expression in the dioecious herb Mercurialis annua

Plant reproductive traits are widely understood to be responsive to the selective pressures exerted by pollinators, but there is also increasing evidence for an important role of antagonists such as herbivores in shaping these traits. Many dioecious species show leaky sex expression, with males and females occasionally producing flowers of the opposite sex. Here we show that leaky sex expression in both males and females of the wind-pollinated dioecious herb Mercurialis annua (Euphorbiaceae) is enhanced in response to simulated herbivory, increasing the probability and the degree of leakiness in both sexes. We also found that leakiness was greater in larger females but not in larger males. We discuss hypotheses for a possible functional link between herbivory and leaky sex expression, and consider what herbivory-induced leakiness might imply for the evolutionary ecology of plant reproductive systems, especially the breakdown of dioecy and the evolution of hermaphroditism.

ecology↗

bioRxiv2017

Toxicity of 2 pg ethynylestradiol in brown trout embryos (Salmo trutta)

Endocrine disrupting chemicals are a threat to natural fish populations in the aquatic environment. Their toxicity is usually discussed relative to concentrations in the water the fish are exposed to. In the case of the synthetic compound 17-alpha-ethynylestradiol (EE2), a common and persistent estrogen, concentrations around 1 ng/L have repeatedly been found to induce toxic effects in fish. Here, we used brown trout (Salmo trutta) from a natural population to study EE2 take up and how it affects early life-history. We collected adults during the spawning season, produced 730 families in vitro (to control for potential maternal and paternal effects on embryo stress tolerance), and singly raised 7,300 embryos (in a 2 mL static system) that were either exposed to one dose of EE2 at 1 ng/L (i.e., 2 pg/embryo) or sham-treated. We found that EE2 concentration did not significantly change over a period of 3 months in control containers without embryos. Embryos took up most of the 2 pg EE2 within about 4 weeks at 4.6{degrees}C. EE2 treated embryos experienced higher mortality, delayed hatching of the survivors, and had reduced size at hatching. Our findings suggest that the toxicity of EE2 is often underestimated when discussed at the level of concentrations in water only.

ecology↗