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Intraspecific and intraclutch variability of avian egg
Králová, Barbora ; Jelínek, Václav (advisor) ; Sedláček, Ondřej (referee)
Egg-laying birds have a huge variation between species in terms of number, size, pigmentation, but also in the speckled nature of the eggs. Bird eggs vary not only between species, but also within species, even within a clutch. It is only recently that more speculation has begun about the possible causes of intraspecific variation. Hypotheses about intraclutch variation started to emerge even later. This thesis presents and describes some of the hypotheses dealing with egg variability. One of the most significant factors affecting intraspecific variability is food availability, which in turn affects female fitness. For intraclutch variability, most studies focus on the difference between the last egg and other eggs within the clutch. In many cases, the last egg has a size difference, but also a different amount of pigment compared to the other eggs in the clutch, which are not significantly different from each other.
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Maternal effect on body size in the Madagascar ground gecko Paroedura picta
Píchová, Veronika ; Starostová, Zuzana (advisor) ; Vrtílek, Milan (referee)
The maternal effect is a phenotypic process in which the mother influences her offspring through her phenotype, her behaviour and also through the environmental condition that affect her. This non-genetic effect can have a variety of manifestations. One way that mothers of oviparous vertebrates can affect their offspring is through the size of their eggs. This thesis aims to investigate whether and how female of the gecko Paroedura picta can influence the growth and final body size of their offspring. Females of this species can reproduce at an early age and increase the size of their eggs during their lifetime. Therefore, I investigated whether this difference in energy allocation to the eggs would affect the size of the hatchlings and subsequently their growth and final body size. The result shows that the eggs mass increases with female body size and larger hatchlings were born from larger eggs. However, smaller hatchlings from smaller eggs grow faster compared to larger ones and exhibit so called compensatory growth. Only the sex affects final body size of an individual, but this effect is not apparent at hatching. In this gecko, the maternal effect is only apparent in the egg size and hatchling size but it does not affect the growth or final body size of an offspring later in the ontogeny.
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Trade-off between egg size and number at the level of bird families
Špaldoňová, Alexandra ; Hořák, David (advisor) ; Reif, Jiří (referee)
Trade-off between offspring size and number belongs to the most discussed concepts in the life history theory. The aim of this study was to elucidate the relationship between egg size, clutch size and female body mass at the family level in bird's and to examine whether there is the relationship between offspring size and number and life history traits specific for particular bird families. From published sources, I collected data about 5.073 species belong in 146 families. Most species of birds lay smaller clutches, on average three eggs. In 112 families from 130 tested eggs size was positively correlated with female body mass. There is evidence that egg size and clutch size are inversely related in 83 families from 130 tested but only for 34 families was significant. The relationship exists independently of female body mass across bird families and this suggests a trade-off between these traits. The relationship between the strength and shape of egg size-number correlations and life history characteristics of bird families was not frequent. According to results, the strength of correlation seems to be related to development mode and diet type. The negative egg size-number correlation is stronger when incubation period and fledging time is longer and in birds with longer lifespan. The...
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