THE ECOLOGICAL AND EVOLUTIONARY EFFECTS OF ENDOCRINE DISRUPTING COMPOUNDS ON SEXUALLY SELECTED TRAITS IN MALE GUPPIES

Male mating signals convey important mate-quality information to females and are regulated by androgens. Endocrine disrupting compounds (EDCs) are chemicals that interfere with proper hormonal functioning in exposed animals, causing altered hormone levels and resulting in changed reproductive characteristics, including mating signals. Altered signals can have ecological implications by influencing population and community dynamics and evolutionary implications via trans-generational reduction in signal reliability leading to reduced preference and eventual loss of the signal trait. I examined the effects of exposure to environmentally relevant concentrations of atrazine, a widely used herbicide and EDC, on mating signals and behaviors in male guppies, a sexually dimorphic freshwater fish. Guppies were exposed either during adulthood or embryonic development. Prolonged atrazine exposure during adulthood reduced the size of the carotenoid-based ornament, the number of courtship displays performed, and aggression towards competing males. Embryonic exposure did not affect survival to adulthood and the time to develop male-specific morphologies. But there was a trend for smaller genitalia, and the ornament size was significantly increased. Possible increases in immunocompetence as a result of slight estrogenecity may have allowed for greater carotenoid allocation to the ornament. Embryonic exposure also resulted in reduced courtship behavior, forced copulatory attempts and aggression towards competitors; female guppies found these males less attractive. The low dose had the strongest effects with embryonic exposure, indicating the importance of low-dose exposures. These studies highlight the effects of low and environmentally relevant doses of atrazine on mating signals and behaviors in exposed wildlife. A mathematical model was used to understand the evolutionary effects of EDCs on the optimal allocation of carotenoids between ornament and immunocompetence. Animals obtain carotenoids through their diet, and allocate some of this to enhance immune function and the rest to ornaments for mate attraction. The model replicates the disruption of carotenoid-based ornaments as a result of EDC-exposure, and predicts that signal reliability will be reduced. The model simulates an evolutionary shift in the optimal allocation if exposure spanned multiple generations, but signal reliability is not restored. Including additional selective forces like predation further suppresses signal reliability

Environmentally Realistic Exposure to the Herbicide Atrazine Alters Some Sexually Selected Traits in Male Guppies

Male mating signals, including ornaments and courtship displays, and other sexually selected traits, like male-male aggression, are largely controlled by sex hormones. Environmental pollutants, notably endocrine disrupting compounds, can interfere with the proper functioning of hormones, thereby impacting the expression of hormonally regulated traits. Atrazine, one of the most widely used herbicides, can alter sex hormone levels in exposed animals. I tested the effects of environmentally relevant atrazine exposures on mating signals and behaviors in male guppies, a sexually dimorphic freshwater fish. Prolonged atrazine exposure reduced the expression of two honest signals: the area of orange spots (ornaments) and the number of courtship displays performed. Atrazine exposure also reduced aggression towards competing males in the context of mate competition. In the wild, exposure levels vary among individuals because of differential distribution of the pollutants across habitats; hence, differently impacted males often compete for the same mates. Disrupted mating signals can reduce reproductive success as females avoid mating with perceptibly suboptimal males. Less aggressive males are at a competitive disadvantage and lose access to females. This study highlights the effects of atrazine on ecologically relevant mating signals and behaviors in exposed wildlife. Altered reproductive traits have important implications for population dynamics, evolutionary patterns, and conservation of wildlife species

Pearson's correlation coefficients between variables of mating behavior in the presence of competing males.

<p>Pearson's correlation coefficients between variables of mating behavior in the presence of competing males.</p

Treatment effects on mating behaviors.

<p>(A) The number of courtship displays performed to a female per 10 minute trial, and (B) the number of mating attempts per 10 minute trial. Treatments are labeled as follows: pooled control+DMSO group = “controls”, atrazine low-dose = “AtzL”, atrazine high-dose = “AtzH”, ethynyl estradiol = “EE”. Arrows between groups in panel A denote planned orthogonal contrasts. These are not shown for panel B because none of the contrasts were significantly different.</p

Treated males' behaviors in relation to paired control males' behaviors.

<p>Treated males—those belonging to DMSO, atrazine low-dose, atrazine high-dose and ethynyl estradiol groups—were the focals, while the paired male from the control group was the opponent. For each response variable, the x- and y-axes have the same measure and units. Results of the ancova corresponding to each panel: (A) Proximity: treatment, <i>F</i>_{3, 36.7} = 2.71, <i>P</i> = 0.059; opponent's response, <i>F</i>_{1, 37.1} = 5.47, <i>P</i> = 0.025; treatment×opponent's response, <i>F</i>_{3, 36.9} = 0.65, <i>P</i> = 0.59; (B) number of courtship displays: treatment, <i>F</i>_{3, 39} = 4.71, <i>P</i> = 0.007; opponent's response, <i>F</i>_{1, 39} = 0.01, <i>P</i> = 0.92; treatment×opponent's response, <i>F</i>_{3, 39} = 0.23, <i>P</i> = 0.88; (C) number of mating attempts: treatment, <i>F</i>_{3, 39} = 5.63, <i>P</i> = 0.0026; opponent's response, <i>F</i>_{1, 39} = 19.97, <i>P</i><0.0001; treatment×opponent's response, <i>F</i>_{3, 39} = 0.18, <i>P</i> = 0.91; (D) number of attacks: treatment, <i>F</i>_{3, 28.9} = 8.25, <i>P</i> = 0.0004; opponent's response, <i>F</i>_{1, 33.1} = 14.41, <i>P</i> = 0.0006; treatment×opponent's response, <i>F</i>_{3, 28.4} = 10.37, <i>P</i><0.0001; (E) number of aggressive displays: treatment, <i>F</i>_{3, 30} = 4.10, <i>P</i> = 0.015; opponent's response, <i>F</i>_{1, 34.9} = 0.72, <i>P</i> = 0.40; treatment×opponent's response, <i>F</i>_{3, 32.4} = 0.06, <i>P</i> = 0.98.</p

Treatment effects on change in proportion of body area covered by orange.

<p>Negative numbers suggest reduction in area of orange, while positive numbers suggest increase in area of orange. Treatments are labeled as follows: pooled control+DMSO group = “controls”, atrazine low-dose = “AtzL”, atrazine high-dose = “AtzH”, ethynyl estradiol = “EE”. Arrows between groups denote planned orthogonal contrasts.</p

Intercept and slope estimates of the treated males' behaviors in relation to those of the paired control males for each treatment group, as generated by the ancova.

<p>*Intercepts and slopes of treatment groups that are significantly different (<i>P</i><0.05) from those of the DMSO group.</p

Factors determining habitat choice of the smooth-coated otter, Lutra perspicillata in a South Indian river system

This study has characterized spraint sites of the smooth-coated otter in the Cauvery Wildlife Sanctuary. Otters use specific sites on land (‘otter sites’/‘spraint sites’) for feeding and social activities; ‘non-otter sites’ are those not used by the otters. Various habitat parameters were identified and assessed. Otter sites varied significantly from non-otter sites, and comprised of loosely packed sand and rock, and lacked hard-packed sand, stone, gravel, vegetation and canopy cover. We believe these site features are important in facilitating grooming, and are prominent territorial markers. Otters avoided areas with high levels of anthropogenic disturbance, though avoidance was temporal rather than spatial. This study has categorized the preferred habitat of otters, which is of importance to conservation