acase@tulane.edu / Anthropogenic noise is an evolutionarily recent phenomenon and many animals respond by changing the pitch and timing of their vocalizations to avoid masking. A benefit to modifying a vocal mating signal in the context of noise is increased transmission distance. This same modification may pose a fitness cost if that signal feature is also sexually selected. Bird song is a well-studied sexual signal used in territory defense and mate attraction. Physically difficult to produce components of song are thought to be honest signals of male quality. One such trait is a male's ability to maximize the rate of note production at a given frequency bandwidth; this tradeoff is known as vocal performance. Studies have shown modifications to song in the context of noise, specifically to trill rate and bandwidth. Costs of these modifications may include increased conflict with neighboring males, which could potentially lead to decreased body condition, loss of a territory, or less time spent attracting a female. Few studies have investigated this tradeoff between environmentally induced selection (i.e. natural selection) and social selection (i.e. sexual selection) on song in an urban landscape. Therefore, a gap remains in our knowledge of the consequences on fitness of urban song adaptation for signalers. Using the white-crowned sparrow (Zonotrichia leucophrys) in the San Francisco Bay Area of California, the objectives of my dissertation research include 1) testing if vocal performance is a salient signal for white-crowned sparrows, 2) testing if receivers are responding specifically to variation in trill rate or bandwidth, and 3) testing the effect of ambient noise level on receiver assessment of vocal performance. Overall, my dissertation research suggests that both anthropogenic and natural soundscapes shape the evolution of song and receiver behavior. Modifications to song structure that increase signal detection come at the cost of decreased signal salience for male competitors. Additionally, anthropogenic noise appears to change how males utilize vocal performance. Therefore, species living in noisy areas may face consequences of decreased fitness over time due to masked honest signals and increased male-male conflict. / 1 / Jennifer N. Phillips

In Annie Proulx's interview with Charlie Rose, she states that her stories come "from place." Ecocriticism has been the predominant lens with which to understand Proulx's work; however, ecocriticism's nebulous tenets and theoretical deficiencies perpetuate sentimental pastoralism of geographical determinism. The shaping impact of Wyoming's environment in Proulx's work lends itself to an evolutionary perspective. Proulx's fiction, like evolutionary theory, examines humanity's unique, reciprocal relationship with nature. The evolutionary approach provides readers with a framework to understand the human relationship to our environment, a theme Proulx's work examines. This approach also augments current criticism that notes the importance of place but does not utilize the relevant framework of evolution. Current evolutionary theory provides the theoretical framework necessary to shed light on the relationship between Proulx's colorful characters and the environment that shapes them. Utilizing this evolutionary framework and textual analysis, I examine two short stories, "The Half-Skinned Steer" and "Wamsutter Wolf."

Sexual selection drives the evolution of male morphology, life history, physiology, and behaviour across taxa. Here I examine the mechanisms of sexual selection that arise at various stages in mating interactions to identify congruence or conflict between the traits selected by choice and competition. I first examine plasticity of developing male Australian redback spiders (Latrodectus hasselti) and show that male metabolic rates vary adaptively to facilitate the scramble to reach virgins. Next, I show that females cease sex pheromone production after mating and re-advertise receptivity later in their reproductive season effectively creating two windows in which males may compete. I show that females discriminate against males that do not meet a threshold courtship duration suggesting that courtship is the trait selected through choice. However, male-male competition leads to reductions in courtship effort provided to females. During the first window paternity is split equally if rival males mate in quick succession with a virgin female. However, if the second mating is delayed, there is a strong bias in the paternity of the second male. A delay in the second mating is beneficial to females as it reduces longevity costs of polyandry. However, delays in the initial mating decrease female longevity, likely because of elevated metabolic rates of virgins. My research shows that the trait favoured by female choice is in opposition to selection via male-male competition. Females’ sex pheromone production yields windows during which mating will optimize female, but not male, fitness. Studies that isolate the mechanisms of sexual selection are valuable in that they can identify the traits under selection. However, my research shows that considering these processes in isolation can lead to incorrect inferences about the net effect of sexual selection.

Sexual selection drives the evolution of male morphology, life history, physiology, and behaviour across taxa. Here I examine the mechanisms of sexual selection that arise at various stages in mating interactions to identify congruence or conflict between the traits selected by choice and competition. I first examine plasticity of developing male Australian redback spiders (Latrodectus hasselti) and show that male metabolic rates vary adaptively to facilitate the scramble to reach virgins. Next, I show that females cease sex pheromone production after mating and re-advertise receptivity later in their reproductive season effectively creating two windows in which males may compete. I show that females discriminate against males that do not meet a threshold courtship duration suggesting that courtship is the trait selected through choice. However, male-male competition leads to reductions in courtship effort provided to females. During the first window paternity is split equally if rival males mate in quick succession with a virgin female. However, if the second mating is delayed, there is a strong bias in the paternity of the second male. A delay in the second mating is beneficial to females as it reduces longevity costs of polyandry. However, delays in the initial mating decrease female longevity, likely because of elevated metabolic rates of virgins. My research shows that the trait favoured by female choice is in opposition to selection via male-male competition. Females’ sex pheromone production yields windows during which mating will optimize female, but not male, fitness. Studies that isolate the mechanisms of sexual selection are valuable in that they can identify the traits under selection. However, my research shows that considering these processes in isolation can lead to incorrect inferences about the net effect of sexual selection.

This study shows the importance of the basic spectro-temporal song parameters in territorial contests between male songbirds. Chiffchaff and willow warbler were selected as model species for their phylogenetic and ecological similarity, strong territorial behaviour, but very different singing styles. We found that bigger males of both species sing lower pitched songs and that males of both species adjust their behaviour according to song pitch of their rival simulated by playback. Thus, it seems that both species use song pitch to acoustically assess the body size of their rivals. We also show that song length and syllable rate are important features of the song, probably signalling short-term motivation to escalate territorial conflict.

Past research suggests association between basal steroid hormone testosterone level and its changes with some individual characteristics (especially some behavioral manifestations of dominance and aggression) or different outcomes of male-male competition. This relationship is usually (in accordance with evolutionary theory) interpreted as the consequence of different individual prerequisites (or the degree of individual motivation) for high status position including winning a male-male competition. The aim of this study was to test the adequacy of measuring jealousy reaction in adolescent boys by way of changes in salivary testosterone level and finding their associations with some individual characteristics mentioned by researchers. For the purpose of measuring basal testosterone level and changes in this hormone level during the competition for a mate which simulated the internet mating and changes in this hormone after being informed of their failure in this competition, the boys who participated in our study provided three salivary samples. For finding associations of basal testosterone level and these hormonal changes with some individual characteristics, the boys filled in a set of questionnaires (EATQ-R, the short version of IPIP, EBIS, ISJS, RSPQ, Rosenberg Self-esteem Scale and expanded...

Past research suggests association between basal steroid hormone testosterone level and its changes with some individual characteristics (especially some behavioral manifestations of dominance and aggression) and its changes within male-male competition. This relationship is usually (in accordance with evolutionary theory) interpreted as the consequence of different individual prerequisites (or the degree of individual motivation) for high status position including winning a male- male competition. The aim of this study was to test the adequacy of measuring jealousy reaction in adolescent boys by way of changes in salivary testosterone level and finding their associations with some individual characteristics mentioned by researchers. For the purpose of measuring basal testosterone level before starting the experiment and changes in its level following the jealousy stimulus within a competition for a mate which simulated the internet mating and changes in its level after being informed of their failure in this competition, the boys who participated in our study provided three salivary samples (the samples were provided after 15 minutes after the stimuli). For finding associations of basal and mean testosterone level and these hormonal changes with some individual characteristics, the boys filled in...

Ainda que existam diversos registros de formas extremas de dimorfismo sexual, a função do alongado quarto par de pernas nos machos de muitas espécies de opiliões permanece desconhecida. Neste estudo, testamos quatro previsões sobre a hipótese de que a seleção sexual está direcionando o alongamento do quarto par de pernas nos machos de Longiperna zonata e Promitobates ornatus: (1) o coeficiente alométrico do comprimento do fêmur IV em machos será maior do que o das fêmeas; (2) machos com pernas IV mais compridas vão residir próximos a grupos de fêmeas; (3) machos envolvidos em interações agressivas terão fêmures mais compridos do que o tamanho médio da população; (4) a diferença de tamanho de perna entre os oponentes será menor do que a diferença esperada entre pares de machos escolhidos ao acaso na população. Como o previsto, o coeficiente alométrico do fêmur IV foi significativamente maior em machos do que em fêmeas nas duas espécies. O comprimento do fêmur IV está positivamente relacionado à chance de um macho ser encontrado próximo a um grupo de fêmeas. Finalmente, a média do comprimento do fêmur IV dos machos envolvidos em brigas foi significativamente maior que a de machos selecionados ao acaso da população. Adicionalmente, a média da diferença de tamanho entre pares de machos que brigaram foi significativamente menor que a média da diferença de tamanho de perna entre pares de machos selecionados ao acaso na população. Assim, a seleção sexual na forma de competição entre machos parece estar direcionando o dimorfismo sexual extremo no comprimento do fêmur nessas duas espécies de opiliões. / Although there are many reports of extreme forms of sexual dimorphism in harvestmen, the function of the elongated fourth pair of legs in males of many species remains unknown. We tested four predictions to address the hypothesis that sexual selection is driving the enlargement of the fourth pair of legs in males of Longiperna zonata and Promitobates ornatus: (1) the allometric coefficient of femur IV length in males will be higher than in females; (2) males with longer legs IV will reside closer to groups of females; (3) males involved in aggressive interactions will have longer femur IV than the population average size; (4) the size difference between contenders will be smaller than the difference expected between randomly chosen pairs of males in the population. As predicted, the allometric coefficient of femur IV length was significantly higher in males than in females of both species. Femur IV length was positively related to the chance of a male being found close to a group of females. Finally, the mean femur IV length of the males involved in fights was significantly larger than the mean of random samples of males from the population, and the average difference between male contenders was smaller than the average random expected difference of the population. Therefore, sexual selection in the form of male-male competition seems to be driving the extreme sexual dimorphism in femur length in these species.

Darwinian sexual selection predicts that males with the most extravagant secondary sexual traits suffer elevated mortality. Although correlative evidence has generally not borne this idea out, recent research, including a field cricket study, showed that investment in sexually selected traits is costly to survival. I investigated male survival, ornamentation (song) and mating success in a North American grylline, Gryllus pennsylvanicus, to test the generality of previous work and highlight the importance of ecology differences to resource allocation. As the calling songs of older male G. pennsylvanicus are highly attractive to females, in Chapter 2 I tested whether male age correlated with calling song and found a weak but statistically significant correlation, thus leaving open the possibility that choosy females use an age-based indicator mechanism. In Chapter 3, I tested the condition dependence of male survival and calling effort. In contrast to previous work, I found that high condition males both called more and lived longer than low condition males, although there was no trade-off between survival and calling effort. The substantial condition dependence of calling effort suggests that calling effort is under strong directional selection. In Chapter 4 I tested whether female mating preferences resulted in strong selection on male calling effort. I also tested for the condition dependence of female mating preferences. I found that female choosiness was condition-dependent, but the rank of preferred male songs (preference function) was not. Both low and high condition females preferred high calling effort over low calling effort song. In Chapter 5 I tested for evidence of nonlinear selection on male survival that might explain the nonlinear pattern of male investment in survival seen in Chapter 3 (i.e. male survival leveled-off with increasing condition). I found that socially experienced females, but not virgin and naive females, exerted linear selection on male age. I discuss these and the other results of my thesis in the context of previous work on field crickets and condition-dependent ornamentation. Finally, Appendix A reports results that confirm ancient Chinese cultural knowledge that large headed male crickets are more successful in male-male combat.

Darwinian sexual selection predicts that males with the most extravagant secondary sexual traits suffer elevated mortality. Although correlative evidence has generally not borne this idea out, recent research, including a field cricket study, showed that investment in sexually selected traits is costly to survival. I investigated male survival, ornamentation (song) and mating success in a North American grylline, Gryllus pennsylvanicus, to test the generality of previous work and highlight the importance of ecology differences to resource allocation. As the calling songs of older male G. pennsylvanicus are highly attractive to females, in Chapter 2 I tested whether male age correlated with calling song and found a weak but statistically significant correlation, thus leaving open the possibility that choosy females use an age-based indicator mechanism. In Chapter 3, I tested the condition dependence of male survival and calling effort. In contrast to previous work, I found that high condition males both called more and lived longer than low condition males, although there was no trade-off between survival and calling effort. The substantial condition dependence of calling effort suggests that calling effort is under strong directional selection. In Chapter 4 I tested whether female mating preferences resulted in strong selection on male calling effort. I also tested for the condition dependence of female mating preferences. I found that female choosiness was condition-dependent, but the rank of preferred male songs (preference function) was not. Both low and high condition females preferred high calling effort over low calling effort song. In Chapter 5 I tested for evidence of nonlinear selection on male survival that might explain the nonlinear pattern of male investment in survival seen in Chapter 3 (i.e. male survival leveled-off with increasing condition). I found that socially experienced females, but not virgin and naive females, exerted linear selection on male age. I discuss these and the other results of my thesis in the context of previous work on field crickets and condition-dependent ornamentation. Finally, Appendix A reports results that confirm ancient Chinese cultural knowledge that large headed male crickets are more successful in male-male combat.