7 Abstract Bird nests protect eggs and nestlings, allowing the parents to leave their offspring and subsequently return to them. Their thermoregulatory properties reduce energetic costs of incubation and brooding of nestlings. For all these reasons, nests are key structures for the reproduction of a majority of avian species and as such they should be subject to natural selection. Several hypotheses describing selection pressures which affect the size of nests or some of their parts have been suggested. In my PhD thesis, I investigated some of them in the great reed warbler (Acrocephalus arundinaceus) - an open nesting passerine species with very variable nest size. For this purpose, I used a large dataset of several hundred measured great reed warbler nests, nest enlargement experiments and an experiment with artificial nests. In accordance with previous studies, we did not find that nest size affects the probability of common cuckoo (Cuculus canorus) brood parasitism, while it was influenced by other factors, such as timing of breeding, reed density around the nest and nest visibility from the nearest potential cuckoo perch site. More interestingly, we found that cuckoos adjust their nest-searching strategy in relation to availability of host nests. When host nests were scarce, cuckoos parasitized all of...

In many species carotenoid-based ornaments plays fundamental role in sexual selection. It is believed that carotenoid-based ornaments act as indicators of individual quality and condition during mate-choice, as associations between their expression, individual fintess and various condition indicators were observed. Despite the long-term research, mechanisms ensuring signalling honesty remain unknown. Currently, the most accepted hypothesis suggests antioxidant properties of carotenoids, and, therefore, a trade-off between their allocation to ornamentation or defence against free radicals. The antioxidant function of carotenoids in vivo was challenged in birds, however, and alternative hypotheses were proposed, assuming either carotenoid loss due to free-radical oxidation, or harmful (pro- oxidant) effects of high carotenoid levels in the body, or interconnection of metabolic pathways for both, the carotenoid conversion and homeostatic control of mitochondrial respiration and redox state. These hypotheses assume differing allocation of carotenoids under elevated oxidative stress, which we tested using experimental manipulations of oxidative state and carotenoid intake in adult male zebra finches (Taeniopygia guttata). The results are inconsistent with all the alternative hypotheses, but partly...

Human mate choice is far from random. Assortative mating can be either positive (homogamy), when people prefer and choose partners with self-similar characteristics, or negative (heterogamy, complementarity), when people prefer self-dissimilar partners. Over one hundred years of research, it has been shown that people generally couple based on the principle of homogamy. This thesis seeks to address the following two goals. First, it critically reviews the current state of knowledge in positive assortative mating (in particular, empirical support, factors affecting homogamy, mechanisms of homogamy, relationship and genetic impact of homogamy, and methodological pitfalls of research). This section includes theoretical papers deal with further mechanisms of assortative mating (homogamy, imprinting-like effect, heterogamy, complementarity). Second, the thesis provides further test of assortative mating in 'ideal partners' (preferences) and actual partners, in the context of sex, sexual orientation (heterosexual and non-heterosexual), and population (Brazil and Czech Republic). Results of these studies show that the principle of homogamy is valid irrespective of sex and population. However, they find a stronger tendency for homogamy in actual partners among heterosexuals than in homosexuals, although...

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,...

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In meiner Dissertation untersuche ich das Paarungs- und Fortpflanzungsverhalten des Europäischen Grasfrosches (Rana temporaria) in einem evolutionären Kontext. Mein Ziel ist es zu verstehen, welche Mechanismen zur Bildung von Paaren führen, ob die Partnerwahl die Paarungsmuster erklärt, die wir beobachten können, und ob es evolutive Vorteile gibt, die sich aus der Paarung mit einem bestimmten Partner ergeben. Die Suche nach und die Konkurrenz um Paarungspartner führt zur Entwicklung verschiedener Paarungssysteme, Strategien und Taktiken, um den Reproduktionserfolg während der gesamten Lebensdauer zu erhöhen. Das Paarungsverhalten wird durch natürliche und sexuelle Selektion beeinflusst, wobei beide in unterschiedliche Richtungen wirken können. Für die meisten Individuen ist das Überleben unerlässlich, um sich so oft wie möglich zu reproduzieren, und dadurch die reproduktive Gesamtfitness zu erhöhen. Andererseits könnte ein auffälliges Verhalten bei der Fortpflanzung das Prädationsrisiko erhöhen. Der Akt der Paarung selbst kann bereits mit Risiken verbunden sein, welche sich auf die Überlebensraten auswirken können. Durch sexuelle Selektion könnten bestimmte sekundäre Geschlechtsmerkmale begünstigt werden, entweder aufgrund von Vorteilen im Wettbewerb innerhalb eines Geschlechts (intrasexuell), oder aufgrund spezifischer Präferenzen zwischen den Geschlechtern (intersexuelle Selektion). Damit sich die Partnerwahl entwickeln kann, muss der gewählte Paarungspartner Vorteile aufweisen, von denen der wählende Partner profitiert, denn die Wahl ist mit energetischen Kosten und zeitlichem Aufwand verbunden. Als Frühlaicher muss der Europäische Grasfrosch mit einem eingeschränktem Paarungszeitraum umgehen. Die Männchen konkurrieren um den Zugang zu Weibchen und es wird angenommen, dass sich Weibchen während der Paarung und Reproduktion passiv verhalten, da der hohe "Männchen-Überschuss" keine Wahl zulassen würde. Aus evolutionärer Sicht sollten Weibchen jedoch das wählerische Geschlecht sein und entscheiden mit wem sie sich paaren, da sie mehr Energie in die Eierproduktion investieren. / In my thesis, I examine the mating and reproductive behaviour of the European Common Frog (Rana temporaria) in an evolutionary context. I aim to understand which mechanisms lead to the formation of pairs, if mate choice shapes the patterns of mating that we can observe and if there are benefits derived from pairing with a specific mate. The search and competition for mating partners lead to the evolution of various mating systems, strategies and tactics to increase lifetime reproductive success. The mating behaviour is influenced by natural and sexual selection, whereby both could act in different directions. For most individuals, survival is essential in order to reproduce as often as possible to increase lifetime reproductive fitness. On the other hand, reproduction could increase predation risk due to conspicuous behaviour and risks associated with mating itself. Sexual selection could favour specific secondary sexual traits, either due to advantages in intrasexual competition, or by specific preferences of the choosy sex (intersexual selection). For mate choice to evolve, there need to be benefits associated with the chosen mating partner, because choosiness involves costs in terms of energy and time constraints during mating. As an explosive breeder, the European Common Frog has to deal with time constraints during the short breeding season. The males are competing for the access to females and it is assumed that females are passive during breeding due to a high male-biased operational sex ratio. However, from an evolutionary perspective females should be the choosy sex and should decide with whom to mate, as they invest more energy into the production of eggs.

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S’approvisionner en nourriture est essentiel à la survie et au succès reproducteur. Lorsque les animaux font face à des changements environnementaux brutaux, ils doivent s’ajuster rapidement à leur nouvel environnement et parfois même innover dans leur façon de s’approvisionner. Des processus comportementaux et cognitifs, tels que l’innovation et l’apprentissage, permettent aux animaux d'intégrer de nouveaux comportements à leur répertoire comportemental afin de s'adapter de façon optimale. Les performances cognitives varient entre les individus d’une même population et bien que des études récentes se soient intéressées aux causes de ce phénomène, de convaincantes évidences sont manquantes afin d’expliquer pourquoi ces variations sont maintenues. Au cours de ce mémoire, les questions des pressions de sélection s'exerçant sur les performances d’alimentation par une tâche motrice nouvelle sont abordées afin de mieux comprendre l'évolution des capacités cognitives au sein d'une population captive de diamants mandarins (Taeniopygia guttata). Nous avons tout d'abord testé si les femelles diamants mandarins modifient leurs préférences d'accouplement après avoir observé la performance d'alimentation par une tâche motrice nouvelle des mâles. Afin de déterminer si les femelles sont capables de discriminer entre les mâles sur la base de leur capacité cognitive, nous avons également évalué les performances d’apprentissage de chacune d’elles. En effet, des études ont suggéré qu’il peut être coûteux, spécialement en terme de temps, de discriminer entre des partenaires potentiels sur cette base. La généralisation d’une préférence pour un mâle performant à d’autres mâles possédant le même phénotype permettrait la réduction de ces coûts. Nous avons donc finalement testé si les femelles diamants mandarins peuvent généraliser leur préférence après avoir observé les performances d’alimentation pour une tâche motrice nouvelle d’un mâle. Nos résultats suggèrent que les femelles diamants mandarins ne peuvent évaluer les capacités cognitives d’un mâle par l’intermédiaire de traits indicateurs. Toutefois, nous avons démontré qu’une observation directe des performances d’alimentation d’un mâle guide le choix d’appariement des femelles. Également, nous avons montré que les femelles peuvent généraliser l’apparence du mâle le plus performant et utiliser cette information lors de l’évaluation de nouveaux mâles. La relation entre les performances cognitives et le choix de partenaire pourraient s’expliquer par exemple par une meilleure exploitation de l’habitat, mais nécessite des études plus approfondies. / Successful foraging is essential for survival and reproductive success. When animals face rapidly change due to climate change or anthropogenic habitat destruction, they are force to quickly adjust their behaviour such as foraging. Innovation and learning, two processes related to cognitive functions, are know to allow animals to incorporate novel behaviours into their behavioural repertoires and thus to facilitate optimal responses to environmental change. Cognitive performance vary between and within individuals and although several studies have rencently addressed the causes, convicing evidences for why inter-individual variations in cognitive performance are maintained in a population are still lacking. During my Masters, I investigated different selective pressures acting on foraging performance on a novel motor task to better understand the evolution of cognitive abilities in a captive population of zebra finch (Taeniopygia guttata). Firstly, we investigated whether female zebra finches modify their mating preferences after having observed the foraging performance of males on a novel motor task. We also assessed each bird’s learning performance in a color associative task in order to check whether females could discriminate between the two males based on their learning performance. Discriminating among mates based on their cognitive ability might be very costly for females, especially in terms of time. Therefore, one way to reduce the cost of assessing mate would be to generalize their preferences to any male with the same phenotype as the most efficient observed individual. We finaly investigated whether female zebra finches can generalize their mating preferences after having observed a male’s foraging performance on a novel motor task. Our findings suggest that female zebra finches would be unable to assess male cognitive ability indirectly via morphological traits. However our results demonstrate that direct observation of the males’ performance on a foraging task can guide female mating preferences. We also demonstrates that female zebra finches can generalize the appearance of the male that is the most efficient at solving a motor task and then use this information to assessing new males. The relationship between cognitive performance and mating preference might be mediated throught habitat exploitation for example, but requires further investigation.

Evolution is a most fascinating feature of all living things in our world. The means of organismal evolution are diverse, comprising mainly of natural and sexual selection. Both of these phenomena may contribute to evolutionary adaptations in health and disease. The questions of immunity impact on the process of sexual selection and sexual selection for increased anti-parasite resistance are wide issues of the present research in natural sciences. Their clarification requires multidisciplinarily-based investigation combining a variety of partial results into a single united paradigm. My co-workers and I have chosen several specific issues to study, in order to fill some of the important gaps of the current knowledge. We proposed the Carotenoid maintenance handicap hypothesis to point out that optimisation instead of maximisation of the carotenoid intake and ornamental display may be physiologically convenient for the individual. In Scarlet rosefinch (Carpodacus erythrinus) we confirmed the role of the carotenoid-based ornamental colouration in the process of sexual selection and investigated several partial aspects of the association between immunogenetics, immune function, health and the ornament expression and mate choice. In Zebra finch (Taeniopygia guttata) we have shown that the present way of...