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.A mphibians are a model animal system for studying endocrine disruption in nature (1). Wild amphibians show evidence (such as testicular oocytes) of feminizing endocrine disruption in human-modified environments (2-7). With few exceptions (6, 7), research on amphibians has focused on agricultural landscapes (2, 4, 5) and the effects of pesticides such as atrazine (2,8). In parallel, endocrine disruption in fish has been observed in the context of chemical gradients associated with sources of endocrine disrupting chemicals (EDCs) such as municipal wastewater treatment facility discharges (9-11). These studies imply that endocrine disruption in aquatic systems is caused predominantly by industrial-or municipalscale activities. However, recent work has revealed that suburban neighborhoods also may be hotspots for endocrine disruption, and green frogs [Rana (Lithobates) clamitans] from "backyard ponds" have been reported (6, 7) to exhibit higher frequencies of feminizing endocrine disruption (testicular oocytes in males) than frogs from other land uses (forest, agricultural, and urban). Endocrine disruption appears to be a ubiquitous phenomenon in suburban ponds, with testicular oocytes observed in male green frogs at all 34 suburban ponds studied to date (6, 7). The causes of endocrine disruption in suburban landscapes have not yet been studied. Although some ...

Phenotypic matches between plants and their pollinators often are interpreted as examples of reciprocal selection and adaptation. For the two co-occurring plant species, Heliconia bihai and H. caribaea in the Eastern Caribbean, we evaluated for five populations over 2 years the strength and direction of natural selection on corolla length and number of bracts per inflorescence. These plant traits correspond closely to the bill lengths and body masses of their primary pollinators, female or male purple-throated carib hummingbirds (Eulampis jugularis). In H. bihai, directional selection for longer corollas was always significant with the exception of one population in 1 year, whereas selection on bract numbers was rare and found only in one population in 1 year. In contrast, significant directional selection for more bracts per inflorescence occurred in all three populations of the yellow morph and in two populations of the red morph of H. caribaea, whereas significant directional selection on corolla length occurred in only one population of the red morph and one population of the yellow morph. Selection for longer corollas in H. bihai may result from better mechanical fit, and hence pollination, by the long bills of female E. jugularis, their sole pollinator. In contrast, competition between males of E. jugularis for territories may drive selection for more bracts in H. caribaea. Competitive exclusion of female E. jugularis by territorial males also implicates pollinator competition as a possible ecological mechanism for trait diversification in these plants.

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