Endosulfan affects pheromonal detection and glands in the male red-spotted newt, Notophthalmus viridescens

A comprehensive overview of the effects of urbanisation on sexual selection and sexual traits

Urbanisation can affect mating opportunities and thereby alter inter- and intra-sexual selection pressures on sexual traits. Biotic and abiotic urban conditions can influence an individual's success in pre- and post-copulatory mating, for example through impacts on mate attraction and mate preference, fertilisation success, resource competition or rival interactions. Divergent sexual selection pressures can lead to differences in behavioural, physiological, morphological or life-history traits between urban and non-urban populations, ultimately driving adaptation and speciation. Most studies on urban sexual selection and mating interactions report differences between urban and non-urban populations or correlations between sexual traits and factors associated with increased urbanisation, such as pollution, food availability and risk of predation and parasitism. Here we review the literature on sexual selection and sexual traits in relation to urbanisation or urban-associated conditions. We provide an extensive list of abiotic and biotic factors that can influence processes involved in mating interactions, such as signal production and transmission, mate choice and mating opportunities. We discuss all relevant data through the lens of two, non-mutually exclusive theories on sexual selection, namely indicator and sensory models. Where possible, we indicate whether these models provide the same or different predictions regarding urban-adapted sexual signals and describe different experimental designs that can be useful for the different models as well as to investigate the drivers of sexual selection. We argue that we lack a good understanding of: (i) the factors driving urban sexual selection; (ii) whether reported changes in traits result in adaptive benefits; and (iii) whether these changes reflect a short-term ecological, or long-term evolutionary response. We highlight that urbanisation provides a unique opportunity to study the process and outcomes of sexual selection, but that this requires a highly integrative approach combining experimental and observational work.

Anticipated effects of abiotic environmental change on intraspecific social interactions

Social interactions are ubiquitous across the animal kingdom. A variety of ecological and evolutionary processes are dependent on social interactions, such as movement, disease spread, information transmission, and density-dependent reproduction and survival. Social interactions, like any behaviour, are context dependent, varying with environmental conditions. Currently, environments are changing rapidly across multiple dimensions, becoming warmer and more variable, while habitats are increasingly fragmented and contaminated with pollutants. Social interactions are expected to change in response to these stressors and to continue to change into the future. However, a comprehensive understanding of the form and magnitude of the effects of these environmental changes on social interactions is currently lacking. Focusing on four major forms of rapid environmental change currently occurring, we review how these changing environmental gradients are expected to have immediate effects on social interactions such as communication, agonistic behaviours, and group formation, which will thereby induce changes in social organisation including mating systems, dominance hierarchies, and collective behaviour. Our review covers intraspecific variation in social interactions across environments, including studies in both the wild and in laboratory settings, and across a range of taxa. The expected responses of social behaviour to environmental change are diverse, but we identify several general themes. First, very dry, variable, fragmented, or polluted environments are likely to destabilise existing social systems. This occurs as these conditions limit the energy available for complex social interactions and affect dissimilar phenotypes differently. Second, a given environmental change can lead to opposite responses in social behaviour, and the direction of the response often hinges on the natural history of the organism in question. Third, our review highlights the fact that changes in environmental factors are not occurring in isolation: multiple factors are changing simultaneously, which may have antagonistic or synergistic effects, and more work should be done to understand these combined effects. We close by identifying methodological and analytical techniques that might help to study the response of social interactions to changing environments, highlight consistent patterns among taxa, and predict subsequent evolutionary change. We expect that the changes in social interactions that we document here will have consequences for individuals, groups, and for the ecology and evolution of populations, and therefore warrant a central place in the study of animal populations, particularly in an era of rapid environmental change.

Mate choice in a polluted world: consequences for individuals, populations and communities

Pollution (e.g. by chemicals, noise, light, heat) is an insidious consequence of anthropogenic activity that affects environments worldwide. Exposure of wildlife to pollutants has the capacity to adversely affect animal communication and behaviour across a wide range of sensory modalities-by not only impacting the signalling environment, but also the way in which animals produce, perceive and interpret signals and cues. Such disturbances, particularly when it comes to sex, can drastically alter fitness. Here, we consider how pollutants disrupt communication and behaviour during mate choice, and the ecological and evolutionary changes such disturbances can engender. We explain how the different stages of mate choice can be affected by pollution, from encountering mates to the final choice, and how changes to these stages can influence individual fitness, population dynamics and community structure. We end with discussing how an understanding of these disturbances can help inform better conservation and management practices and highlight important considerations and avenues for future research. This article is part of the theme issue 'Linking behaviour to dynamics of populations and communities: application of novel approaches in behavioural ecology to conservation'.

The endocrine disruptor, 17α-ethinyl estradiol, alters male mate choice in a freshwater fish

Among the handful of studies on the behavioural effects of endocrine disrupting chemicals (EDCs), only a few have set out to disentangle the mechanisms underpinning behavioural changes. In fish, previous studies have shown that both visual and chemical cues play an important role in mate choice. As such, contaminant-induced changes in either transmission or perception of mate choice cues could have direct implications for individual's fitness. One widespread contaminant of environmental concern is 17α-ethinyl estradiol (EE2), a synthetic estrogen used in the contraceptive pill. Here, we investigated the impacts of EE2 exposure (28 days; measured concentration 14 ng/L) on visual and chemical communication in wild guppies (Poecilia reticulata). Using a standard dichotomous mate choice assay, we first gave individual males (either control or EE2-exposed) the opportunity to court two size-matched females (one control and one EE2-exposed) using only visual cues. We then introduced chemical cues of females (control and EE2-exposed) to the trial tank. We found that there was no significant effect of EE2-treatment on total time males spent associating with the females, when given only visual cues. There was, however, a significant effect on male courtship behaviour, with both control and EE2-exposed males spending more time performing 'sigmoid' displays towards the visual cues of control females compared to EE2-exposed females. When males were presented with both visual and chemical female cues simultaneously, we found that males spent more time courting control females that were paired with EE2-chemical cues. Not only does our study uncover a previously unknown behavioural impact of EE2-exposure on chemical cues, but demonstrates that EE2-exposure can exert complex effects on visual and chemical communication in a mate choice context. Finally, we contribute to the discussion of intraspecific variability by providing data on the potential trade-offs underpinning contaminant-induced behavioural changes.

Sexual dimorphic responses in wildlife exposed to endocrine disrupting chemicals

Understanding the gender similarities and differences in how organisms respond following exposure to environmental chemicals is important if we are to determine the relative risk of these agents to wildlife and human populations. In this paper, we have chosen to focus on the sex determination and differentiation of fishes, amphibians, and reptiles, because of their close association with the environment and the number of environmental factors (e.g., temperature and endocrine disrupting chemicals) that are known to affect these phenomena in these taxa. We have discussed examples of gender differences in response to exposure to endocrine disrupting chemicals and found gender similarities about as often as we found differences. We found that most studies examined either one sex exclusively, or the experimental design did not include examining the effect of sex as a variable. Given the central role of sex steroid hormones in the sex determination and sexual differentiation of fishes, amphibians, and reptiles, we recommend that future research purposefully include sex as a factor, so that risk assessment by government agencies can address the probable gender differences in effects from exposure to chemicals in the environment.

Methodologies, bioindicators, and biomarkers for assessing gender-related differences in wildlife exposed to environmental chemicals

Male and female organisms may have significant differences in their exposure, toxicokinetics, and response to chemicals, but gender effects have received relatively little attention, often viewed as a confounder rather than of primary importance. In this paper, we examine some of the key issues and methodologies for incorporating gender in studies of the effects of chemicals on wildlife, and explore bioindicators and biomarkers of gender effects. Examining gender-related differences in response to chemicals is complicated in wildlife because of the vast array of species, and differences in niches, lifespans, reproductive cycles and modes, and population dynamics. Further, organisms are more at risk in some ecosystems than others, which may increase the magnitude of effects. Only by studying wild animals, especially native species, can we truly understand the potential impact of gender-specific effects of chemical exposure on populations. Several factors affect gender-related differences in responses to chemicals, including exposure, age, size, seasonality, and genetic and phenotypic variation. There are clear examples where gender-related differences have had significant effects on reproductive success and population stability, including destabilization of gamete release in invertebrates, and alterations of endocrine and neuroendocrine system functioning in vertebrates. A wide range of new technologies and methods are available for examining gender-related differences in responses to chemicals. We provide examples that show that there are gender-related differences in responses to chemicals that have significant biological effects, and these gender-related differences should be taken into account by scientists, regulators, and policy makers, as well as the public.

Alteration of the chemical environment disrupts communication in a freshwater fish

It is well established that changes to the chemical environment can impair development, physiology and reproductive biology; by contrast, impacts on communication have not been widely reported. This is surprising given that chemical communication is the most widely used sensory modality in nature, and that variation in the chemical composition of the environment is the rule, not the exception. Here, we show that chemically mediated species recognition in a swordtail fish, Xiphophorus birchmanni, can be hindered by anthropogenic disturbance to the signalling environment. Females have a strong preference for conspecific male chemical cues, yet they hybridize in nature with the congener X. malinche. Wild-caught females showed a strong preference for conspecifics when tested in clean water, but failed to show a preference when tested in stream water subject to sewage effluent and agricultural runoff. We hypothesized that this was due to the interaction between chemical communication systems and humic acid (HA), a ubiquitous, natural product elevated to high levels by anthropogenic processes. When exposed to elevated concentrations of HA, female X. birchmanni again lost their preference for conspecific male chemical cues, while visual mating preferences and motivation to mate were retained. Sub-lethal concentrations of seemingly benign substances can thus have a drastic effect on natural populations through their specific impact on communication systems.

Endocrine disrupting contaminants--beyond the dogma

Descriptions of endocrine disruption have largely been associated with wildlife and driven by observations documenting estrogenic, androgenic, antiandrogenic, and antithyroid actions. These actions, in response to exposure to ecologically relevant concentrations of various environmental contaminants, have now been established in numerous vertebrate species. However, many potential mechanisms and endocrine actions have not been studied. For example, the DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] metabolite, p,p -DDE [1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene] is known to disrupt prostaglandin synthesis in the uterus of birds, providing part of the explanation for DDT-induced egg shell thinning. Few studies have examined prostaglandin synthesis as a target for endocrine disruption, yet these hormones are active in reproduction, immune responses, and cardiovascular physiology. Future studies must broaden the basic science approach to endocrine disruption, thereby expanding the mechanisms and endocrine end points examined. This goal should be accomplished even if the primary influence and funding continue to emphasize a narrower approach based on regulatory needs. Without this broader approach, research into endocrine disruption will become dominated by a narrow dogma, focusing on a few end points and mechanisms.