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Extra-pair fertilizations and the opportunity for sexual selection in Barn swallows
Michálková, Romana ; Albrecht, Tomáš (advisor) ; Šálek, Miroslav (referee)
Generally it is assumed, that sexual selection drives the evolution of elaborate traits. The strength of sexual selection has traditionally been attributed to varinace in reproductive success among individuals. This variance is mainly caused by the number of mating partners and the number of sired offspring. Both males and females can increase their reproductive success by alternative reproductive strategies - extrapair copulations and intraspecific brood parasitism. In our study we tested the relationship between male ornamentation and success in extra-pair and within-pair paternity and the total male reproductive success in barn swallow (Hirundo rustica), a socially monogamous species with high levels of extrapair paternity. The results suggest more colourful throat to indicate male reproductive success. Dark rusty males were less often cuckolded and they have higher total fertilization success than drab ones. Tail length did not affect neither within- nor extra-pair fertilization success, however, previous studies have concluded that reproductive success of male barn swallows is positively related to the tail ornaments. Our results confirm that extra-pair paternity considerably increase variance in reproductive success among barn swallow males. We show that within-pair success may increase the...
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Physiological and hormonal mechanisms influencing ejaculate quality in birds
Mojžišová, Kateřina ; Tomášek, Oldřich (advisor) ; Svobodová, Jana (referee)
Sexual selection is an important mechanism of evolution. In addition to precopulatory sexual selection, arising when males compete for female partners, there is also postcopulatory sexual selection (sperm competition), when females copulate with more males. Even though most avian species are socially monogamous, most of them are also partially promiscuous. In such species, sperm competition is an important factor increasing variability in reproductive success between males. Male's success in sperm competition is primarily determined by sperm concentration, total sperm count and morphology and motility of spermatozoa. My bachelor thesis summarizes knowledge about the hormonal a physiological mechanisms that influence semen quality. This is especially the effect of sex and other hormones, physiological and oxidative stress, environmental conditions, antioxidant mechanism and composition of sperm cell membrane. Besides evaluating their influence on ejaculate quality on intraspecific level, I also describe their differences between avian species with respect to the differences of sperm competition.
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Growth and sexual selection in selected representatives of scarabaeoid beetles (Coleoptera: Scarabaeoidea).
Vendl, Tomáš ; Šípek, Petr (advisor) ; Knapp, Michal (referee) ; Skuhrovec, Jiří (referee)
Flower chafers are well-known beetles with apparent sexual dimorphism. Yet, in contrast to other groups of scarab beetles, only little attention has been paid to various aspects of this phenomenon. It concerns also sexual dimorphism in size, which is very common in animals. Although ultimate causes of sexual size dimorphism have been extensively studied, the developmental mechanisms are still only poorly understood. We investigated proximate causes of sexual size dimorphism in several differentially dimorphic flower chafer species. We found that in highly dimorphic species the dimorphism started to develop already in the first instar and tended to accumulate through successive larval development. In contrast, the sexes in species with a relatively low dimorphism diverged in size during only one instar. Moreover, we found variability not only in when the dimorphism arises during development, but also how: sex-related differences in both the instar duration and average growth rate were the proximate causes of sexual size dimorphism. In addition, we showed that the sexes may differ also in growth trajectory - males had relatively longer period of rapid growth than females, even in cases where the absolute development times were similar in both sexes. Further, we focused on systematic survey of sexual...
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Nest construction
Jenšovský, Václav ; Kreisinger, Jakub (advisor) ; Kratochvíl, Lukáš (referee)
The nest is in the life of birds important structure. It is a place where birds kept posterity throughout the period of reproduction. To make it nest offspring suitable place for development, must have a specific structure which is different for each type of variable. Variability, whether at the level of intraspecific and interspecific level and is influenced by several factors. These factors include thermal insulation properties, antipredatory properties, further property to protect the nest before (ecto) parasites, and also the construction of the nest in intraspecific communication as a selectable character sexually. All these factors are aligning differently, but often one factor may disadvantage second and thus reduce the success of rearing offspring. Key words: nest construction, thermal insulation properties, antipredatory properties, ectoparasites, sexual selection
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Acoustic and visual signalization in birds: Identification of key components and their role in sexual selection
Mikula, Peter ; Albrecht, Tomáš (advisor) ; Svobodová, Jana (referee)
This bachelor thesis is focused on describing visual and acoustic signals in birds and their potential role in the process of sexual selection. Evidence that acoustic and visual signals are sexualy selected is summarized. The key characters that can be utilized in comparative studies are determined. In the first chapter of the thesis are briefly outlined mechanisms of sexual selection and evolution of costly secondary male ornamentation. In the second chapter basic avian ornaments (colouration, acoustic signals) are described. The emphasis is on visual and acoustic structures which are costly to produce and serve as honest indicators of individual condition. The third chapter is devoted to the possible trade-offs between visual and acoustic signalization in birds. The last section summarizes hypotheses about potential relationships between visual and acoustic signalization (and trade-offs between these two types of ornamental traits) in relation to changing environmental conditions.
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Condition dependence of sexually selected ornaments in birds
Tomášek, Oldřich ; Albrecht, Tomáš (advisor) ; Verhulst, Simon (referee) ; Šálek, Miroslav (referee)
Sexual ornaments important for mating success in many species are often assumed to evolve as condition-dependent signals of individual quality. Ornament expression can be associated with age and survival, thereby signalling individual viability. Here, we have tested viability signalling function of tail streamers and their importance for within-pair and extra-pair fertilisation success in the European barn swallow (Hirundo rustica rustica). In contrast to previous studies on this subspecies, our data suggest that tail length is not associated with fertilisation success in our population. Instead, the most important predictors of within-pair and extra-pair fertilisation success were female and male age, respectively. Our data supported viability signalling function of male tail streamers, as documented by age-related within- individual increase in their length. There was no evidence for senescence in this trait. Contrary to some previous studies, the viability signalling function of tail streamers was further supported by observed selective disappearance of males with shorter tails. Several physiological mechanisms have been proposed as maintaining signalling honesty. Among them, oxidative stress from highly reactive species (RS), including free radicals, attracted a considerable attention. Given...
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Boar vocalizations and their potential role in sexual selection
Roreitnerová, Daniela ; Linhart, Pavel (advisor) ; Schneiderová, Irena (referee)
The aim of this research was to gather existing knowledge about vocalizations of boars and their potential role in sexual selection. Few studies mainly from the 70s and 80s of the last century suggest that the so-called love song, emitted by males during courtship, could act as a stimulant that triggers mating. However, I did not find any evidence that boars significantly use calls in fights. Most studies deal with pig vocalization in a different context. For this reason, I tried to look at the studies of pig relatives - even-toed ungulates - to better evaluate the potential role of boar vocalizations in sexual selection. In their case, the influence of the calls on the sexual behavior of females and competing males was reported. It is possible to conclude that the role of boar vocalization is probably not that important as in red deers, for example, because boars use calls in short range communication. On the other hand, stimulatory effect on females was found in other species too. Further studies are needed to understand possible function of boar vocalizations that could be used for example in pig breeding to improve the effectiveness of artificial insemination of sows. Powered by TCPDF (www.tcpdf.org)
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Macroecology and macroevolution of birdsong
Mikula, Peter ; Albrecht, Tomáš (advisor) ; Osiejuk, Tomasz S. (referee) ; Šálek, Miroslav (referee)
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...
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Sperm morphology and motility in estrildid finches of the genus Lonchura
Šárová, Markéta ; Reifová, Radka (advisor) ; Frolíková, Michaela (referee)
Sexual selection plays an important role in the evolution of animals. Today we already know that it takes place not only before copulation (precopulatory sexual selection), but also after copulation. This type of sexual selection is called postcopulatory sexual selection, and occurs mainly in promiscuous species, where females mate with multiple males. In this case, sperm competition occurs in the female reproductive tract. To increase the likelihood of their reproductive success, males began to develop surprisingly diverse sperm adaptations at the morphological, physiological, or behavioural levels. These adaptations often affect sperm velocity (motility), which is a key factor for successful egg fertilization. However, the result of reproductive success can also be influenced by females, who may prefer sperm with a certain phenotype in the process of cryptic female choice, and thus, for example, obtain better genes for offspring. In some species, females even can have the ability to sort and store sperm in specialized organs in which the sperms are nourished for some time, and then used to fertilize the egg. Even in this case, the storage of sperm is often affected by sperm morphology. Due to these mechanisms of postcopulatory sexual selection, sperm are under strong selection pressure, which can...
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