Phytoestrogens and avian reproduction: Exploring the evolution and function of phytoestrogens and possible role of plant compounds in the breeding ecology of wild birds

摘要

Phytoestrogens are secondary plant compounds, which can act to mimic estrogen and cause the disruption ofestrogenic responses in organisms. Although there is a substantial body of research studying phytoestrogens,including their mechanisms of estrogenic effects, evolution, and detection in biological systems, little isknown about their ecological significance. There is evidence, however, that an ecological relationshipinvolving phytoestrogens exists between plants and animals—plants may produce phytoestrogens to reducefecundity of organisms that eat them. Birds and other vertebrates may also exploit phytoestrogens to regulatetheir own reproduction—there are well known examples of phytoestrogens inhibiting reproduction in highervertebrates, including birds. Also, common plant stressors (e.g., high temperature) increase the production ofsecondary plant compounds, and, as evidence suggests, also induce phytoestrogen biosynthesis. Theseobservations are consistent with the single study ever done on phytoestrogens and reproduction in wild birds[Leopold, A.S., Erwin, M., Oh, J., Browning, B., 1976. Phytoestrogens adverse effects on reproduction inCalifornia quail. Science 191, 98-100.1, which found that drought stress correlated with increased levels ofphytoestrogens in plants, and that increased phytoestrogen levels correlated with decreased young. Thisreview discusses the hypothesis that plants may have an effect on the reproduction of avian species byproducing phytoestrogens as a plant defense against herbivory, and that birds may "use" changing levels ofphytoestrogens in the vegetation to ensure that food resources will support potential young produced.Evidence from our laboratory and others appear to support this hypothesis.