In this thesis, I investigate the relationship between two variables for which persistent directional sexual selection is an evolutionary driver: condition dependence and sexual dimorphism. This joint dependence on sexual selection predicts that among traits within a given species, greater dimorphism should be associated with stronger condition dependence. Very few studies have tested this prediction, and those that have focus on species with highly exaggerated and strongly dimorphic traits between the sexes. Here, I quantified variation in a suite of morphological traits in a dipteran species – the antler fly, Protopiophila litigata – in which sexual dimorphism is less extensive. I manipulated condition via different larval diets and then quantified the effects on adult body size and shape in both sexes. Across traits, I found that the extent of sexual dimorphism was positively associated with the strength of condition dependence in males but not in females. These results suggest a shared developmental basis to condition dependence and sexual dimorphism in body shape, and suggest that this has arisen via sexual selection in males despite the absence of extremely dimorphic shared traits.

Natal dispersal outcomes are an interplay between environmental conditions and individual phenotypes. Peripheral, isolated populations may experience altered environmental conditions and natal dispersal patterns that differ from populations in contiguous landscapes. We document nonphilopatric, sex-biased natal dispersal in an endangered small mammal, the Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis), restricted to a single mountain. Other North American red squirrel populations are shown to have sex-unbiased, philopatric natal dispersal. We ask what environmental and intrinsic factors may be driving this atypical natal dispersal pattern. We test for the influence of proximate factors and ultimate drivers of natal dispersal: habitat fragmentation, local population density, individual behavior traits, inbreeding avoidance, competition for mates, and competition for resources, allowing us to better understand altered natal dispersal patterns at the periphery of a species' range. A juvenile squirrel's body condition and its mother's mass in spring (a reflection of her intrinsic quality and territory quality) contribute to individual behavioral tendencies for movement and exploration. Resources, behavior, and body condition have the strongest influence on natal dispersal distance, but affect males and females differently. Male natal dispersal distance is positively influenced by its mother's spring body mass and individual tendency for movement; female natal dispersal distance is negatively influenced by its mother's spring body mass and positively influenced by individual tendency for movement. An apparent feedback between environmental variables and subsequent juvenile behavioral state contributes to an altered natal dispersal pattern in a peripheral population, highlighting the importance of studying ecological processes at the both range center and periphery of species' distributions.

This study investigated the hypothesis that universal psychological adaptations produce personality variation when individuals differentially face adaptive problems that shifted the cost-benefit tradeoffs of alternative personality strategies in ancestral environments. The current research tested the hypothesis that psychological adaptations calibrate individual differences in neuroticism as a functional response to social exclusion. If psychological adaptations produce neuroticism in response to social exclusion, and heritable components of individuals' social partner value influence their likelihood of being excluded, then individual differences in social partner value should yield heritable differences in neuroticism. Three conceptually distinct sub-studies tested hypotheses derived from this conceptual framework. Sub-study 1 tested the relationship between individuals' mate value, social exclusion, and neuroticism. Individuals' mate value exhibited both a direct effect on neuroticism and an indirect effect through the experience of social exclusion. Sub-study 2 investigated sexual jealousy as a specialized class of neuroticism in response to infidelity. As predicted, individuals' mate value predicted the likelihood of their partners' infidelity and their own mate guarding behavior. Sub-study 3 manipulated the threat of infidelity to test for functional shifts in neuroticism in response to relationship exclusion. Participants read vignettes describing their mates' certain fidelity, uncertain fidelity, and certain infidelity, and wrote what they would think, feel, say, and do in response to each scenario. An independent sample assessed participants' personalities based on these cognitive, affective, and behavioral responses. As predicted, participants' neuroticism tracked relationship exclusion; participants' neuroticism levels increased with infidelity threat. These findings are consistent with the hypothesis that a universal psychological mechanism adaptively calibrates neuroticism levels in response to relationship exclusion; the certain absence or presence of the adaptive problem of relationship exclusion should deactivate or activate anti-exclusion mechanisms in all individuals. Above this situational effect, under conditions of uncertain infidelity -- in which the threat of infidelity would have ancestrally varied with men's (but not women's) mate value -- men's mate value predicted their neuroticism. Together, these findings support the hypothesis that humans possess psychological adaptations that functionally calibrate neuroticism levels. More broadly, they highlight the heuristic value of an evolutionary adaptationist framework for the study of personality and individual differences. / text

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O dimorfismo sexual varia consideravelmente entre populações dentro de uma mesma espécie. Essa variação na direção e na magnitude do dimorfismo sexual é, em parte, devida às diferenças sexuais na respostas plásticas às condições e aos recursos ambientais. Por meio de experimentos em laboratório, sabe-se que a temperatura e a disponibilidade de alimento são fatores importantes na geração de variações morfológicas inter-individuais e que seus efeitos diferem entre machos e fêmeas. Usamos indivíduos da tesourinha Labidura xanthopus (Dermaptera) coletados em 20 localidades ao longo da costa brasileira para investigar como o tamanho corporal e o tamanho do armamento de machos e fêmeas variam em um gradiente natural de temperatura. O tamanho do corpo diminuiu com o aumento da temperatura, mas o dimorfismo sexual se manteve constante ao longo do gradiente de temperatura. Para o tamanho do armamento, encontramos uma relação negativa para machos e positiva para fêmeas. Conseqüentemente, a magnitude do dimorfismo sexual no tamanho do armamento diminuiu ao longo do gradiente de temperatura. Para entender o efeito da disponibilidade de alimento sobre a expressão de características morfológicas em cada um dos sexos, manipulamos a dieta durante o desenvolvimento de indivíduos provenientes de uma população de clima tropical e uma de clima temperado. Independente da população, o dimorfismo sexual foi causado por diferenças sexuais na dependência de condição. Machos e fêmeas diferiram não apenas na magnitude da resposta, mas também na direção. Em relação ao comprimento relativo dos fórceps, em particular, os resultados obtidos em laboratório não apóiam que a variação encontrada em campo se deve à disponibilidade de alimento. Outros fatores que não levamos em consideração, tais como densidade populacional, podem exercer um papel importante na resposta de machos e fêmeas em relação ao tamanho do armamento. Por fim, mais estudos experimentais comparando populações com diferenças marcantes de condições ambientais poderão lançar luz sobre quais fatores ecológicos podem ter favorecido a evolução do dimorfismo sexual dependente de condição / Sexual dimorphism varies considerably among populations within species. This variation in the direction and magnitude of sexual dimorphism is partially explained by sexual differences in phenotypically plastic responses to environmental conditions and resource availability. Laboratory experiments have already shown that temperature and food availability are important factors promoting inter-individual morphological variation and that their effects differ between males and females. We used individuals of the earwig Labidura xanthopus (Dermaptera) collected from 20 Brazilian localities to investigate how body size and weapon size of males and females vary across a natural temperature gradient. Body size decreased with increasing temperature, but sexual size dimorphism remained constant across the temperature gradient. For weapon size, we found a negative relationship for males and a positive relationship for females. Thus, the magnitude of sexual dimorphism in weapon size decreased across the temperature gradient. To understand the effect of food availability on the expression of morphological traits in each sex, we manipulated the diet of individuals from a tropical and temperate population. Regardless of the population, sexual dimorphism was caused by sex-differences in condition dependence. Males and females differed not only in the magnitude of their responses, but also in the direction. Regarding the relative length of the forceps, in particular, our results do not support the interpretation that the morphological variation observed in the field is explained by differences in food availability. Other factors not considered here, such as population density, may play an important role in determining weapon size variation in males and females under natural conditions. Finally, more experimental studies comparing populations with marked differences in environmental conditions may shed light on which ecological factors have favored the evolution of condition-dependent sexual dimorphism

O dimorfismo sexual varia consideravelmente entre populações dentro de uma mesma espécie. Essa variação na direção e na magnitude do dimorfismo sexual é, em parte, devida às diferenças sexuais na respostas plásticas às condições e aos recursos ambientais. Por meio de experimentos em laboratório, sabe-se que a temperatura e a disponibilidade de alimento são fatores importantes na geração de variações morfológicas inter-individuais e que seus efeitos diferem entre machos e fêmeas. Usamos indivíduos da tesourinha Labidura xanthopus (Dermaptera) coletados em 20 localidades ao longo da costa brasileira para investigar como o tamanho corporal e o tamanho do armamento de machos e fêmeas variam em um gradiente natural de temperatura. O tamanho do corpo diminuiu com o aumento da temperatura, mas o dimorfismo sexual se manteve constante ao longo do gradiente de temperatura. Para o tamanho do armamento, encontramos uma relação negativa para machos e positiva para fêmeas. Conseqüentemente, a magnitude do dimorfismo sexual no tamanho do armamento diminuiu ao longo do gradiente de temperatura. Para entender o efeito da disponibilidade de alimento sobre a expressão de características morfológicas em cada um dos sexos, manipulamos a dieta durante o desenvolvimento de indivíduos provenientes de uma população de clima tropical e uma de clima temperado. Independente da população, o dimorfismo sexual foi causado por diferenças sexuais na dependência de condição. Machos e fêmeas diferiram não apenas na magnitude da resposta, mas também na direção. Em relação ao comprimento relativo dos fórceps, em particular, os resultados obtidos em laboratório não apóiam que a variação encontrada em campo se deve à disponibilidade de alimento. Outros fatores que não levamos em consideração, tais como densidade populacional, podem exercer um papel importante na resposta de machos e fêmeas em relação ao tamanho do armamento. Por fim, mais estudos experimentais comparando populações com diferenças marcantes de condições ambientais poderão lançar luz sobre quais fatores ecológicos podem ter favorecido a evolução do dimorfismo sexual dependente de condição / Sexual dimorphism varies considerably among populations within species. This variation in the direction and magnitude of sexual dimorphism is partially explained by sexual differences in phenotypically plastic responses to environmental conditions and resource availability. Laboratory experiments have already shown that temperature and food availability are important factors promoting inter-individual morphological variation and that their effects differ between males and females. We used individuals of the earwig Labidura xanthopus (Dermaptera) collected from 20 Brazilian localities to investigate how body size and weapon size of males and females vary across a natural temperature gradient. Body size decreased with increasing temperature, but sexual size dimorphism remained constant across the temperature gradient. For weapon size, we found a negative relationship for males and a positive relationship for females. Thus, the magnitude of sexual dimorphism in weapon size decreased across the temperature gradient. To understand the effect of food availability on the expression of morphological traits in each sex, we manipulated the diet of individuals from a tropical and temperate population. Regardless of the population, sexual dimorphism was caused by sex-differences in condition dependence. Males and females differed not only in the magnitude of their responses, but also in the direction. Regarding the relative length of the forceps, in particular, our results do not support the interpretation that the morphological variation observed in the field is explained by differences in food availability. Other factors not considered here, such as population density, may play an important role in determining weapon size variation in males and females under natural conditions. Finally, more experimental studies comparing populations with marked differences in environmental conditions may shed light on which ecological factors have favored the evolution of condition-dependent sexual dimorphism

Secondary sexual traits play an irreplaceable role in the reproduction of a range of animals and are used as quality and fitness sensors during pairing of individuals. Expression of these traits, ornamentes, can correlated with an individual's personal and behavioral strategies. In the case of melanin ornaments, not only the relationships with personal individuals are considered, but there is the possible connections with stress resistance and the level of stress responses too. This hypothesis is based on the pleiotropic effect of the melanocortin system, which can be used during melanogenesis but also in the production of hormones that contribute to range of stress responses. The aim of this work was to clarify the relationship between an individual's ornaments, his stress response and individuality in the barn swallows (Hirundo rustica rustica). In this work the relationship between selected ornaments and the stress reaction of the organism, stressed glucose levels measured 15 minutes after a stress stimulus, was tested. Both sexes showed a correlation between area of white tail spots and stress response. Only for males a relationship with the length of outermost tail feathers was found and a correlation with the color saturation of feathers on the throat was shown for females. The second part of...