Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

[Truncated abstract] The assumption that facial attractiveness signals mate quality is central to current evolutionary theories of human sexual selection. Evidence for direct links between attractiveness and mate quality is, however, scarce, and the exact nature of mate quality remains the subject of debate. Mate quality may include genetic diversity, because genome-wide diversity has been linked to individual fitness, and diversity within the Major Histocompatibility Complex (MHC) has been associated with immunocompetence and health in many species. This thesis investigates whether individual genetic diversity plays a role in human sexual selection. The main aim is to examine whether MHC diversity, compared to genetic diversity in general, is especially important for mate preferences, health and mating success. The four studies herein are based on data collected from a large sample of heterosexual, Caucasian males and females. Participants were photographed, provided a DNA sample, and completed questionnaires regarding sexual history and health. Genetic diversity was calculated as both mean heterozygosity (H) and standardised mean-d2 (d2), separately for 12 MHC microsatellite loci and 11 nonMHC loci. The photographs were rated for various attractive features by opposite-sex raters. The first study investigated whether MHC diversity influences preferences for facial appearance in a potential mate, and if so, are they specific to the MHC and are they mediated by specific facial characteristics? I found that MHC-H, but not nonMHCH, positively predicted male facial attractiveness, and that this relationship was mediated by facial averageness. For females, nonMHC-d2 predicted facial symmetry, and potentially attractiveness. These findings indicate that faces contain visual cues to mate quality in both males and females, providing support for evolutionary theories that our preferences are adaptations for identifying mates of high quality. ... Measuring them both allowed me to tease apart their effects on mate preferences, and on health and mating success. Indeed, the MHC appears to be especially important in sexual selection as MHC diversity predicted female mate preferences after controlling for nonMHC diversity, and MHC dissimilarity predicted male mate preferences after controlling for nonMHC dissimilarity. Moreover, although MHC diversity did not appear to influence males’ preference for females, it did predict female mating success, suggesting that males also attend to MHC-related cues, although perhaps non-facial cues, when seeking mates. Additionally, nonMHC diversity predicted both male preferences for female faces and health, suggesting that such preferences are adaptive. Importantly, by providing direct links between facial attractiveness and biological markers of individual quality, genetic diversity, these results support the commonly held assumption that facial attractiveness signals mate quality.

Made available in DSpace on 2016-12-23T13:47:34Z (GMT). No. of bitstreams: 1 Giovanni Ribeiro Loiola.pdf: 928388 bytes, checksum: 78051849b34ce27fbc12468e5563d739 (MD5) Previous issue date: 2008-02-22 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Heteragrion consors Selys (Odonata: Megapodagrionidae) é uma espécie de libélula que habita riachos em matas fechadas. Machos permanecem pousados em poleiros as margens de córregos, enquanto fêmeas adquirem parceiros e visitam locais de oviposição. A variação diária da abundância de machos e da temperatura ambiental, o orçamento temporal dos machos; o comportamento reprodutivo e sistema de acasalamento da espécie, a distribuição espacial dos machos e hipóteses de que o comportamento (pousado inerte, pousado flexionando o abdômen, voo de deslocamento, voo de forrageio e voo agonístico) e tamanho corporal dos machos afetam a permanência e mobilidade em poleiros preferenciais e determinam estratégias territoriais distintas foram investigadas. Para alcance dos objetivos, incluindo testes de hipótese, uma população de H. consors foi monitorada por 40 dias na Reserva Biológica de Duas Bocas, Espírito Santo, registrando-se o comportamento de 152 indivíduos, localização no ambiente e tomando-se medidas corporais de 63 indivíduos. A espécie apresenta tolerância térmica limitada a alta incidência de radiação solar e recorre a poleiros sombreados nos horários mais quentes do dia, evitando o aquecimento corporal excessivo. Analisando-se 35 horas de amostragem comportamental, machos permanecem pousados e inertes a maior parte do tempo ( x =98,17%, DP= ± 7,58%), utilizando o mesmo poleiro por vários dias consecutivos ( x =4,06 dias; DP= ± 4,08; amplitude=1-20 dias), raramente realizando voos de deslocamento ( x =0,16%; DP= ± 0,85%), forrageio ( x =0,58%; DP= ± 1,06%) e agonístico ( x =0,34%; DP= ± 2,48%); ou acasalamentos (0,4 acasalamentos/dia). O macho permanece em contato com a fêmea em tandem précopulatório ( x =4,55 minutos; DP= ± 5,13; n=27,3 minutos), cópula ( x =15,98 minutos; DP= ± 7,13; n=79,9 minutos) e guarda pós-copulatória com contato ( x =10,07 minutos; DP= ± 7,8; n=40,3 minutos) de longa duração, evitando a perda do sucesso reprodutivo e competição espermática com rivais. As características comportamentais investigadas e o tamanho corporal não exerceram influência sobre a capacidade de monopolização de pontos específicos no ambiente, embora machos com tamanho corporal menor frequentem poleiros mais altos (r=-0,3; P=0,01; n=135). Não foi possível dissociar diferentes estratégias territoriais com base nas características comportamentais investigadas e tamanho corporal dos machos, mas conflitos aéreos e permanência no mesmo poleiro por vários dias podem significar territorialidade. A seleção sexual (intrasexual e intersexual) aparentemente opera em intensidade baixa na espécie, que apresenta baixo grau de dimorfismo sexual. O sistema de acasalamento não se baseia na monopolização de recursos pelos machos, consistindo em um sistema de acasalamento por encontro limitado, com encontros raríssimos entre machos e fêmeas e disponibilidade abundante de locais oviposição. O impacto da longevidade dos machos sobre o sucesso reprodutivo merece investigação futura, pois tende a ser característica influente na aquisição de parceiras, havendo maior vantagem para machos que vivam mais e explorem maior número de eventos reprodutivos extremamente raros. A abundância de fêmeas, gordura e simetria corporal dos machos, características do substrato submerso nos segmentos com poleiros e a velocidade da corrente hídrica também são variáveis que podem definir a permanência dos machos em um mesmo poleiro e a visitação de fêmeas, merecendo também futuras pesquisas / Heteragrion Consors Selys (Odonata: Megapodagrionidae) is a species of dragonfly inhabits streams in dense forests. Males remain resting perches on the banks of streams, while females acquire partner and visit places of oviposition. The daily variation of the abundance of males and ambient temperature, the time budget of males, the reproductive behavior and mating system of the species, the spatial distribution of males and assumptions that behavior (perching inert, perching flexing the abdomen, transition flight, foraging flight and agonistic flight) and body size of males affect retention and mobility in preferred roosts and determine distinct territorial strategies were investigated. To achieve these goals, including hypothesis tests, a population of H. Consors was monitored for 40 days in Duas Bocas Biological Reserve, Espírito Santo, southeastern region of Brazil, registering the behavior of 152 individuals, location in the environment and taking body measurements of 63 individuals. The species has a limited thermal tolerance to high incidence of solar radiation and uses shaded perches in the hottest times of the day, avoiding excessive body heat. Analyzing the 35 hours of sampling behavioral male inert and remain resting most of the time ( x =98.17%, SD= ± 7.58%), using the same perch for several consecutive days ( x =4.06 days; SD= ± 4.08; range=1-20 days), rarely performing transition flights ( x =0.16%, SD= ± 0.85%), foraging flights ( x =0.58%, SD= ± 1,06%) and agonistic flights ( x =0.34%, SD= ± 2.48%), or mating (0.4 matings/day). The male remains in contact with the female pre-copulatory tandem ( x =4.55 minutes, SD= ± 5.13, n=27.3 minutes), copulation ( x =15.98 minutes, SD= ± 7.13, n=79.9 minutes) and contact post-copulatory guarding ( x =10.07 minutes, SD= ± 7.8, n=40.3 minutes) of long duration, avoiding the loss of reproductive success and sperm competition with rivals. Behavioral characteristics investigated and body size had no influence on the ability to monopolization of specific points in the environment, although males with smaller body size perches attend higher (r=-0.3, P=0.01, n=135). It was not possible to separate different spatial strategies based on behavioral characteristics investigated and body size of males, but air conflicts and stay on the same perch for several days can mean territoriality. Sexual selection (intrasexual and intersexual) apparently operates at low intensity in the species, which has a low degree of sexual dimorphism. The mating system is not based on the monopolization of resources by males, consisting of an encounter-limited mating system, with rare encounters between males and females and abundant availability of oviposition sites. The impact on the longevity of male reproductive success deserves further investigation, because it tends to be characteristic influential in acquiring partner, with greater advantage for males to live longer and explore more reproductive events extremely rare. The abundance of females, fat and body symmetry in males, characteristics of the substrate submerged in segments with perches and speed of the water current are also variables that can determine the permanence of males in the same perch and visitation of females, also deserves further research

Darwin was troubled by elaborate male traits observed in many species that are seemingly maladaptive for survival, the peacock’s tail being the most iconic of all. He wrote "The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick" because it challenged his theory of evolution by natural selection for adaptive traits. The extreme length of the tail may render a peacock more vulnerable to predation and therefore maladaptive for survival. To account for the evolution of apparently maladaptive traits he proposed the theory of sexual selection, wherein, traits that directly enhance mating success may be selected for, either as weapons in male-male competition for mates or as ornaments preferred by females. Male and female elephants in the proboscidean evolutionary radiation have had tusks and show extreme exaggeration in size and form. However, tusk in the Asian elephant (Elephas maximus) is sexually dimorphic as it is expressed only in the males, hinting at a possibility that opposing selection (sexual selection advantage to males and natural selection disadvantage to females) may have been the processes behind this pattern of tusk expression. Intriguingly, tuskless males (male dimorphism with respect to tusk) also occur at fairly high frequencies in some Asian elephant populations (∼50% in norteastern India and ∼95% in Sri Lanka). Theory states that dimorphic males can also occur in a population in stable frequencies as a consequence of sexual selection. I explored sexual selection on elephant tusks as possible mechanism leading to the observed patterns of tusk dimorphism in the elephants. All elephant populations on earth have been harvested for ivory, therefore, artificial selection (selective poaching of tusked elephants for ivory) is another possible cause of tusk dimorphism. I developed mathematical models of population genetics, population dynamics and conducted field observations of mating behavior of Asian elephant in Kaziranga National Park, Assam to understand the evolution of tusk dimorphism in elephants. Darwin’s sexual selection theory was controversial when proposed in 1871 and continues to remain so in 2014. In the introduction of my thesis I have discussed Darwin’s two classical mechanisms of sexual selection, namely, male-male combats for mates and female mate choice based on male traits. The latter was viewed with considerable skepticism by his con-temporary Alfred Russell Wallace and more recently deemed "fundamentally flawed" by Joan Roughgarden. Therefore, I have also discussed the arguments against female mate choice for male traits found in literature. I have reviewed current knowledge about sexual selection for sexually dimorphic male traits of body size and musth, in the African and Asian elephant and state why I have hypothesized that tusks may also be under sexual selection. Sexually selected traits are expected to be genetically determined, therefore, I explored mathematically (Chapter 1) the genetic basis of evolution of sexual dimorphism. Fisher proposed that sexually selected male display traits originate in both the sexes but are suppressed in the females by modifier genes, when the trait becomes deleterious to females. Thus, sexually antagonistic selection on a trait and sex-specific gene expression can lead to the evolution of sexual dimorphism. Tusk is sexually monomorphic in the probocideans that are ancestral to both the African (Loxodonta africana) and Asian elephant (Elephas maximus). Tusk continues to remain monomorphic in the African elephant but has become sexually dimorphic in the Asian elephant. Tusk, therefore could be a sexually selected male trait that evolved according to the Fisherian model. Intriguingly, tuskless males occur at very high frequencies in some Asian elephant populations. The tusked and tuskless male morphs could be alternate male mating strategies, occurring at evolutionarily stable frequencies. Alternatively, the observed male tusk dimorphism, could be a consequence of artificial selection against tusked individuals, due to selective harvest of tusked males. Furthermore, male African elephants are more intensely poached for ivory than female elephants. Yet the frequency of tuskless individuals has increased more rapidly among females than in males. In essence, sexual dimorphism could be evolving among such poached populations. Is such rapid, contemporary evolution of sexual dimorphism, possible through the Fisherian modifier gene mechanism? A 2-loci genetic model (with X-linked trait gene and an autosomal modifier gene) (Rice 1984), a slight variant of the model (with X-linked modifier gene, and an autosomal trait gene) and an entirely autosomal model, were analyzed for the rate of evolution of sexual dimorphism, under different selection pressures for tusk possession. Negative frequency dependent selection was introduced into the model of tusk evolution in accordance with Gadgil’s model for the evolution of male dimorphism as consequence of sexual selection (Gadgil 1972). In two of the 2-loci models (in which tusk gene in autosomal), tusklessness evolved much more rapidly in females than in males, under equal negative selection pressures. The models predict several combinations of time-lines and negative selection pressures for effecting a particular change in the frequency of tusklessness. Model predictions were com-pared with observed changes in the frequency of female tusklessness, in one South Ugandan, African elephant population (∼2% to 10% in 5 to 9 generations) and male tusklessness (∼5% to 50% in 25 to 40 generations) in one north eastern Indian, Asian elephant population. The models predict strong selection pressures of 30% to 50% reduction in fitness, that can effect an 8% increase in tusklessness, in the African elephant population, within time-lines of 9 to 5 generations (∼225 to 125 years) respectively. For the male Asian elephants, natural selection against tusked males on an already sexually dimorphic population, must have been in operation and shifted the population to 5% male tusklessness. The models predict that artificial selection with 20 to 30% fitness cost to tusked males, operating for 40 to 25 generations (∼1000 to 600 years) respectively, can further shift the population from ∼5% to ∼50% tusklessness. Asian elephant populations may already have been in a transient phase of evolution, tending towards tusklessness, with recent artificial selection hastening the process. The two major pre-dictions from this modeling exercise are (1) artificial selection could have played a significant role in the evolution of male tusk dimorphism in the Asian elephant (2) a lack of or very mild current sexual selection on tusks in the male Asian elephant. Both these predictions may be empirically verified. Chapters 2 and 3 are attempts at empirical verification of prediction (1) and Chapters 4 and 5 of prediction (2). From historical references to elephant harvest in Assam, we do know that artificial selection has been in operation, but whether it has played a major role in causing male tusk dimorphism needs to be established. It may be possible to detect signatures of significant past harvest from current demographic structure of an elephant population. Sustained biased harvesting of a particular sex and or age class from an animal population alters the sex ratio and age structure (relative proportion of individuals in each age and sex class) of a population considerably (Sukumar 1989). It may be possible to back infer the harvest scenario by studying the deviation of current age and sex ratios from natural age and sex ratios. In Chapter 2, I explored models of population dynamics under different harvest regimes and its effect on age and sex ratios. I described a method to infer unknown harvest rates and numbers from age and sex ratios, namely, adult female to male ratio, male old-adult to young-adult ratio, and proportion of adult males in the population using Jensen’s(2000) 2-sex, density-dependent Leslie matrix model. The specific combination of male and female harvest rates and numbers can be deter-mined from the history of harvest and an estimate of population size. I validated this model with published data on age and sex ratios of one Asian and African elephant population with fairly reliable data on elephant harvest as well. In Chapter 3, I applied this model to the demographic data that I collected from a wild Asian elephant population in Kaziranga National Park, Assam, India (where more than 50% of the adult males are tuskless). Male polymorphism of sexually-selected male traits occur at stable frequencies in populations of several species. The different male morphs of the trait are hypothesized to be alternate male mating strategies with equal life time reproductive fitness. Male Asian elephants of Kaziranga National Park, Assam are dimorphic with respect to tusk possession: ∼50% of the males are tuskless (and are locally called makhnas). Makhnas could be trading tusk for either longevity, larger body size, testicular volume and or duration of musth as alternate mating strategies. On the other hand makhnas may have increased to a very high frequency primarily due to selective removal (captures for domestication and hunting for ivory) of tusked males from the population for centuries. The aim of Chapter 3 was to examine the role of artificial selection in the evolution of makhnas. Prolonged male-biased harvest(removal from the population) is bound to alter the demographic structure of the population and leave a signature of the intensity and type of harvest on the residual population structure. The Kaziranga elephant population was considered as representative of elephant populations of north east India; A harvest modeling approach (described and validated in Chapter 2) was used to infer unknown harvest of elephants from demographic parameters estimated by sampling this elephant population during 458 field days in the dry season months of 2008–2011. The Kaziranga elephant population appears to have been harvested approximately for the past 700 to 1000 years with adult tusked males being harvested at approximately twice the rate of adult tuskless males, adult females and their immature offspring of both the sexes. The currently observed high frequency of tuskless males in Kaziranga therefore, may be a consequence of sustained artificial selection against tusked males for several centuries. The previous two Chapters have only examined some mechanisms for the loss of tusks in elephants. I proceeded to examine the possibility of evolution of tusks through Darwin’s mechanisms of male-male competition for mates and female mate choice. Elephant tusks are cited as an example of a male trait that has evolved as a weapon in male-male combats. In Chapter 4 I examined the role of tusks in establishing dominance along with two other known male–male signals, namely, body size and musth (a temporary physiologically heightened sexual state) in an Asian elephant population in northeastern India with equal proportions of tusked and tuskless males. I observed 116 agonistic interactions with clear dominance outcomes between adult (>15 years) males during 458 field days in the dry season months of 2008–2011. A generalized linear mixed-effects model was used to predict the probability of winning as a function of body size, tusk possession and musth status relative to the opponent. A hierarchy of the three male–male signals emerged from this analysis, with musth overriding body size and body size overriding tusk possession. In this elephant population tusk possession thus played a relatively minor role in male–male competition. An important implication of musth and body size being stronger determinants of dominance than tusk possession is that it could facilitate rapid evolution of tuskless males in the population under artificial selection against tusked individuals, which are poached for ivory. If not a weapon, tusks could be a male ornament that female elephants find attractive. I explored the interplay of the three male traits (body size, musth and tusk), male mating strategies and female mate choice in Chapter 5. In some species males obtain mating opportunities by harassment of females. Given the striking size difference between an adult male and female elephant, with males weighing at least 30% more than females, male coercion of females to mate is a possibility. A detailed study of the courtship behavior revealed that overt male harassment of females is rare and the ability of a male to mount and stay mounted on a female for copulation is under female control. Therefore female Asian elephants can exercise choice to mate but this is subtly different from exercising mate choice itself. Age-related male mating strategy (reported for the first time in the Asian elephant) exists in the Kaziranga elephant population and this strategy limits the ability of females to exercise choice. Young males (<25 years) predominantly show a sneak mating strategy. Middle-aged males (25–40 years), when in musth, mate–guarded oestrous females from sneakers and attempted mating but sometimes resorted to sneak mating when out of musth. Old males (> 40 years) attempted mating only during their musth phase and were seldom sneakers. Large/musth males received positive responses from estrous females towards courtship attempts significantly more often than did small/non–musth males. Tusked non–musth males attempted courtship significantly more often than did their tuskless peers, and had a higher probability of receiving positive responses than did tuskless males. A positive response, however, may not translate into mating because of mate–guarding by the dominant male. Females permitted large/musth males to stay mounted significantly longer than small/non-musth males. Musth and large body size may be signals of male fertility. Female mate choice in elephants thus seems primarily for traits that signal direct benefits of assurance of conception. Tusked males may attain sexual maturity faster than tuskless males. Therefore it is worth exploring if tusks function as signals of male fertility when males are young (15 to 25 years); this may be possible through hormonal and behavioral profiling of young tusked and tuskless males from 10 to 20 years of age. Overall all musth and body size appear to play a larger role in enhancing male mating success than tusks. Tusked males appear to have a weak sexual selection advantage (male-male domi-nance and female preference) over their tuskless peers, only in the young age class (15 to 25 years) in this population. Males in this age age class, seldom come into musth that would over-ride tusk as a signal of male dominance. Current sexual selection on tusks in this population, appeared to be insignificant and this may be verified through genetic analysis of paternity success. An important implication of musth and body size being stronger determinants of mating success than tusk possession is that, it could facilitate rapid evolution of tuskless males in the population under artificial selection against tusked individuals, even in a slow breeder such as the elephant. Musth may have evolved much later than tusks in elephants, therefore it is possible that tusks evolved under sexual selection before musth evolved. However, body size, in mammals in gen-eral appear to be under both natural and sexual selection. Gould has shown that the absurdly large and palmate antlers of the extinct Irish elk, scales allometrically with body size (Gould & Lewontin 1979). Phylogenetic studies of elephant evolutionary radiation indicate a general trends towards increase in body-size with size reduction and tendency towards dwarfism occurring only in island habitats (Palombo 2001). Tusk development, which is essentially tooth development may be closely linked to cranium development. Cranium development in turn may be linked to body size through allometric scaling laws. If so, any selection on body size is bound to act on tusk size. I propose that the evolution of elaborate tusks seen in elephants is primarily due to natural and or sexual selection acting on body size, and tusk just hitched a ride with body size. Tusks may be maintained in spite of tuskless males occurring in the population only because of a rather weak sexual selection advantage to tusk possession in contests in which males are symmetrical with respect to body size and musth status.

Birdsong is one of the most astounding natural sounds which profoundly shaped our evolutionary thinking since the 19th century. Despite a strong interest in birdsong for over 100 years, our understanding of birdsong ecology and evolution over large spatial and phylogenetic scales is still very fragmentary. Answering many basic questions requires a global synthesis covering vast diversity of extant bird species and adoption of multidisciplinary approaches. In presented dissertation thesis, my co-workers and I have explored important patterns in macroecology and macroevolution of song in passerines (Order: Passeriformes), the most diverse and widespread bird order. We have focused on three key song phenomena: (1) song complexity, (2) song frequency and (3) the presence of song in female birds. We have exploited birdsong "big data" available on public citizen science databases and other open sources in order to fill several important gaps in the current knowledge. These data were analysed by a combination of phylogenetically-informed cross-species analyses and spatial macroecological approaches. Since the publication of Darwin's seminal work, elaborated songs are generally agreed to be the result of sexual selection. We developed a simple but reliable song complexity metric to explore a global diversity in...

6 ABSTRACT Conditional ornaments plays irreplaceable role in sexual selection in non-small part of by sexual reproduction reproducing animals. Fastidiousness of generating and later also carrying of these ornaments which show condition of their wearer, burdens also metabolism in non-small scale. This thesis tests hypothesis of mutual addiction between conditional ornaments, as the indicators of qualities of individuals and metabolism, as the most significant source of free radicals which are responsible for oxidative stress. The real weight of influence of ornament fastidiousness on organism, resp. on redox state, is tested in this thesis. Manipulations which were performed with individual males of model species should point how much the selected factors correlate each other. The barn swallow (Hirundo rustica) is the model species. Analyses of dates collected during trapping which were realized in breeding seasons in 2012 and 2013 does not show any important trends between observing variables. This fact is confirmed by minimal differences and inconsistent variability of levels of measured antioxidants - oxidoreductases, superoxide dismutase and glutathione peroxidase. The marginal effect of manipulations with one of the conditional ornaments which are presented in model species supports the hypothesis of...

Birdsong is one of the most astounding natural sounds which profoundly shaped our evolutionary thinking since the 19th century. Despite a strong interest in birdsong for over 100 years, our understanding of birdsong ecology and evolution over large spatial and phylogenetic scales is still very fragmentary. Answering many basic questions requires a global synthesis covering vast diversity of extant bird species and adoption of multidisciplinary approaches. In presented dissertation thesis, my co-workers and I have explored important patterns in macroecology and macroevolution of song in passerines (Order: Passeriformes), the most diverse and widespread bird order. We have focused on three key song phenomena: (1) song complexity, (2) song frequency and (3) the presence of song in female birds. We have exploited birdsong "big data" available on public citizen science databases and other open sources in order to fill several important gaps in the current knowledge. These data were analysed by a combination of phylogenetically-informed cross-species analyses and spatial macroecological approaches. Since the publication of Darwin's seminal work, elaborated songs are generally agreed to be the result of sexual selection. We developed a simple but reliable song complexity metric to explore a global diversity in...

Previous studies have shown that physical attractiveness is one of important aspects in mate choice. Facial traits perceived as attractive may be linked to potential mate quality, or more precisely to their reproductive potential, health and ability to invest in his mate and offspring. Mating with individuals with more reactive immune system could lead to higher reproductive success and thus it is possible that visual cues facilitating detection of such traits may have evolved. The main aim of the present thesis was to test a possible association between the reactivity of the immune system response to foreign antigens (stimulated by vaccination) and facial attractiveness perceived by opposite sex individuals. Further, we investigated visual changes occurring during immune system activation. We did not find any association between measures of reactivity of immune system and perceived facial attractiveness. However, participants with activated immune system were rated as significantly less attractive and were significantly paler. Overall, our results suggest that people are sensitive to visual cues to current health status but not to overall quality of the individual. Key Words Facial attractiveness, mate choice, sexual selection; heterozygosity; symmetry; immune system, antigen; disease-avoidance,...

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...

Bei vielen Laubheuschreckenarten produzieren nur die Männchen Gesänge, hauptsächlich um arteigene Weibchen anzulocken und sich mit Rivalen zu messen. Die Produktion der durch sexuelle Selektion ausgewählten akustischen Signale kostet das singende Männchen Energie. Die Gesangsleistung kann aufgrund der unterschiedlichen Körperqualität von Männchen zu Männchen variieren, was zu relevanten Konsequenzen für das Ergebnis der sexuellen Selektion führt. In dieser Arbeit soll die Auswirkung sexueller Selektion auf sekundäre Merkmale der Männchen untersucht werden, wie die Größe der Organe zur Schallproduktion und die Struktur akustischer Signale. Der Fokus liegt dabei auf den Faktoren, die die Qualität des Signalgebers und die Zusammensetzung des sozialen Umfelds bestimmen. Um diese Ziele zu erreichen, werden zwei Laubheuschreckenarten Poecilimon ampliatus und Poecilimon v. veluchianus untersucht. Die morphologischen Befunde zeigen, dass die positive Selektion auf klangproduzierende Strukturen mit der Präferenz von Weibchen für schwerere Männchen übereinstimmt und daher Rückschlüsse von der Körpermasse der Männchen auf die Größe der schallerzeugenden Organe gezogen werden können. Die Ergebnisse der akustischen Daten betonen die entscheidende Relevanz der Kombination verschiedener Umweltfaktoren. Sie zeigen, wie Männchen auf akustische Signale reagieren, die von benachbarten Konkurrenten erzeugt werden, indem sie ihre Signalerzeugung kohärent an die Stärke der Konkurrenz und ihren persönlichen energetischen Status anpassen. Männchen beider Arten zeigen eine interindividuelle Variation in der Fähigkeit, ihre Signalproduktion anzupassen, die sowohl durch Faktoren wie die Körpermasse des Männchens und der Populationsdichte beeinflusst wird. In zukünftigen Untersuchungen könnte der Frage nachgegangen werden, wie Männchen in der Natur von ihrer Kondition abhängige Signale und alternative Verhaltensstrategien entwickeln. / Behaviours and structures related to mating are under sexual selection. Due to their costs, these traits honestly reflect the quality of the signaller. Using structures located on the wings, bushcricket males signal to attract females and repel rivals. Sound performance can vary between individuals of different body conditions, leading to relevant consequences for the outcome of sexual selection. This thesis aims to investigate the effect of sexual selection on secondary male traits, such as the size of sound production organs and the structure of acoustic signals. The focus is on the factors that determine the quality of the signaller and the composition of the social environment. To fulfil the aims, two bushcrickets species were used: Poecilimon ampliatus and Poecilimon v. veluchianus. In P. ampliatus, sexual selection plays a role in determining the size of morphological structures that are responsible for producing female-preferred acoustic signals. A positive relationship between body condition and size of sound-producing organs was found. Heavier and larger males had larger wing and longer stridulatory file with disproportionally longer and less dense stridulatory teeth. A further effect of sexual selection is highlighted during the acoustic contest. In both species, only heavy males shown plasticity in acoustic behaviour. Moreover, the sound produced in competition honestly reflects the males’ body condition. In P. ampliatus heavier males signal at higher effort than lighter males and increased their activity when the light rival was placed at a closer distance. In P. v. veluchianus heavy males increased their signal activity only when the number of light rivals increased. Future endeavour will be to study how males in nature evolve condition-dependent signalling and alternative behavioural strategies.