| 1. |
- Favati, Anna, 1980-
(author)
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The relationship between personality and social dominance in the domestic fowl – a critical perspective
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Social dominance relationships are formed within numerous animal species and reduce costly fights over resources. Dominant individuals often enjoy greater access to important resources such as food and mating partners, and are generally more aggressive, bold, active and explorative compared to subdominant individuals. These behavioural traits can differ among individuals, but they can also be consistent within the individual, thereby describing the individual’s personality type. However, the causal direction of the observed correlation between dominance and personality is not well studied. One possibility is that some personality types have higher chances of obtaining a dominant social position. This would suggest that personality has consequences for fitness. Another possible explanation is that possessing different social positions gives rise to consistent behavioural differences among individuals on various timescales. If social status has a lasting effect on behaviour, social status would constitute a ‘stable state’ that explains some of the diversity of personality types that has been observed in a multitude of animal species. Dominance and personality may also share underlying proximate factors. In this thesis, I investigate the relationship between social dominance and personality using male domestic fowl, Gallus gallus domesticus. The species is group-living with pronounced dominance hierarchies, and dominance increases male access to mating partners. I show that some aspects of personality, exploration, vigilance and in particular aggressiveness, increased a male’s chances of obtaining dominance (paper III, IV, V), and that aggressiveness can be even more important than body weight and ornament size (comb size, paper V) or recent experience of winning or losing (paper IV). Winning a social interaction resulted in an increase in aggressiveness, while a decrease was seen in males that experienced a loss (paper IV). By observing behaviour before and after changes in male dominance relationships, I further show that a recent (2 days earlier) change in social status induced behavioural adjustments to the new social status in activity, exploration and vigilance (paper I). By extending the time of the new social relationship to 3 weeks, I show that such behavioural changes did not continue (paper II). Finally, I show that the social environment during juvenile development had little impact on adult male competitiveness (paper V). Social interactions appear to have several short-term effects on behaviour, but did not contribute significantly to variation and long-term consistency of personality in male fowl. Instead, a male's personality, and in particular his aggressiveness, affected the outcome of dominance interactions. Overall, my studies reveal important consequences of individual differences in behaviour, and contribute to the highly sought-after empirical testing of hypotheses explaining variation in animal personality.
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| 2. |
- Alm Bergvall, Ulrika, 1970-
(author)
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Food choice in fallow deer – experimental studies of selectivity
- 2007
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Doctoral thesis (other academic/artistic)abstract
- In this thesis, I experimentally investigate feeding selectivity in fallow deer (Dama dama), with respect to plant secondary compounds, especially tannins, which can decrease the quality of foods. I found that fallow deer avoided foods with higher amounts of tannic acid and Quebracho tannin, even though the deer ate some high-tannin food. The food choice was strongly dependent on the context in which the food was presented, so that the food choice in relation to tannin content was relative rather than absolute. When high-tannin food occurred at low frequency, the deer ate proportionally less from this type of food, at least when the difference in tannin content between the two foods was large. A basic implication is that an unpalatable plant type could benefit from its unpalatability, especially when occurring at low frequency. In experiments with two patches, the finding of a stronger within- than between-patch selectivity was mirrored in associational effects. First, low-tannin, palatable food was more eaten when occurring in a high-tannin patch, which corresponds to neighbour contrast susceptibility. Second, high-tannin, unpalatable food in a less defended patch was less eaten, which corresponds to neighbour contrast defence. A proximate cause of the associational effects can be the presence of a simultaneous negative contrast, which was experimentally demonstrated in an additional study. Individual differences in selectivity were present early in life and were consistent over five years, and selectivity was correlated with foraging exploratory behaviour. The results from this thesis suggest that fallow deer are selective in their food choice with respect to tannins from the beginning, and that the frequency of occurrence of different foods, but also the distance between foods and the complexity of presentation, influence the food choice. It is also suggested that a foraging behavioural syndrome is present in mammalian herbivores.
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| 3. |
- Stålhandske, Sandra, 1986-
(author)
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Spring Phenology of Butterflies : The role of seasonal variation in life-cycle regulation
- 2016
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Doctoral thesis (other academic/artistic)abstract
- Animals and plants in temperate regions must adapt their life cycle to pronounced seasonal variation. The research effort that has gone into studying these cyclical life history events, or phenological traits, has increased greatly in recent decades. As phenological traits are often correlated to temperature, they are relevant to study in terms of understanding the effect of short term environmental variation as well as long term climate change. Because of this, changes in phenology are the most obvious and among the most commonly reported responses to climate change. Moreover, phenological traits are important for fitness as they determine the biotic and abiotic environment an individual encounters. Fine-tuning of phenology allows for synchronisation at a local scale to mates, food resources and appropriate weather conditions. On a between-population scale, variation in phenology may reflect regional variation in climate. Such differences can not only give insights to life cycle adaptation, but also to how populations may respond to environmental change through time. This applies both on an ecological scale through phenotypic plasticity as well as an evolutionary scale through genetic adaptation. In this thesis I have used statistical and experimental methods to investigate both the larger geographical patterns as well as mechanisms of fine-tuning of phenology of several butterfly species. The main focus, however, is on the orange tip butterfly, Anthocharis cardamines, in Sweden and the United Kingdom. I show a contrasting effect of spring temperature and winter condition on spring phenology for three out of the five studied butterfly species. For A. cardamines there are population differences in traits responding to these environmental factors between and within Sweden and the UK that suggest adaptation to local environmental conditions. All populations show a strong negative plastic relationship between spring temperature and spring phenology, while the opposite is true for winter cold duration. Spring phenology is shifted earlier with increasing cold duration. The environmental variables show correlations, for example, during a warm year a short winter delays phenology while a warm spring speeds phenology up. Correlations between the environmental variables also occur through space, as the locations that have long winters also have cold springs. The combined effects of these two environmental variables cause a complex geographical pattern of phenology across the UK and Sweden. When predicting phenology with future climate change or interpreting larger geographical patterns one must therefore have a good enough understanding of how the phenology is controlled and take the relevant environmental factors in to account. In terms of the effect of phenological change, it should be discussed with regards to change in life cycle timing among interacting species. For example, the phenology of the host plants is important for A. cardamines fitness, and it is also the main determining factor for oviposition. In summary, this thesis shows that the broad geographical pattern of phenology of the butterflies is formed by counteracting environmental variables, but that there also are significant population differences that enable fine-tuning of phenology according to the seasonal progression and variation at the local scale.
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| 4. |
- Tegelaar, Karolina, 1984-
(author)
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Dynamics of the aphid-ant mutualism
- 2015
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Doctoral thesis (other academic/artistic)abstract
- An appreciation of the role of mutualism is essential when studying ecology and evolution in most ecosystems. Information covering aspects of mutualistic interactions can serve as a complement to the somewhat one-sided perspective from the 1950’s and 60’s that is used when teaching biology. In this thesis I applied an in-depth approach in which variation in the interspecific interaction between Aphis fabae aphids and Lasius niger ants was studied both in the field and in the laboratory. An emphasis was put on studies spanning several consecutive aphid generations. This approach revealed important differences between ant tended aphids and those without ants. In the lab, I found an initial decrease in aphid adult size and reproductive investment in the first generations after the start of ant tending, which was followed by a recovery to the pre-tending situation after about four generations. Another laboratory experiment showed an increase in alate (winged aphid) production from exposure to aphid alarm pheromones, and an even stronger decrease in alate production from ant attendance, suggesting that ants have gained the upper hand in an evolutionary conflict over aphid dispersal. Results from a field experiment further emphasized the possibility of negative effects of ants on aphids, showing that ant-tended aphid colonies experienced a higher rate of parasitoid attacks, produced fewer alates and embryos in adult aphids. The thesis highlights the scope for variation in the net effect of the interaction for aphids, and argues that, depending on the environmental circumstances, the interaction may sometimes and perhaps even often not really be a case of mutualism.
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| 5. |
- Aronsson, Marianne, 1978-
(author)
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Colour patterns in warning displays
- 2012
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Doctoral thesis (other academic/artistic)abstract
- In aposematism a prey species use bright colours, often combined with a black contrasting pattern, to signal unprofitability as prey to potential predators. Although there are several different hypotheses about the presence of these internally contrasting patterns, there is little experimental evidence of any beneficial effects. In this thesis I have used bird predators and artificial prey signals to investigate if the contrasting internal patterns in warning displays may have evolved to increase signal efficacy, especially regarding the speed of avoidance learning. In paper I the relative importance of colour and pattern in avoidance learning was studied. The conclusion was that birds primarily attend to colour, not pattern, when learning the discrimination, which was further supported by the results in paper II-IV, all suggesting a secondary role of patterns. In paper II I show that predators may to some degree use patterns for discrimination, if they convey important information about prey quality. The predators showed a hierarchical way of learning warning colour components, where colour is learned to a higher degree than pattern. In paper III I investigate if internal contrasting patterns promote avoidance learning by increasing conspicuousness as prey-to-background contrast does. The study did not support this idea, as the presence of internal black patterns did not improve avoidance learning on a colour matching background. In paper IV, however, I show that the presence of many internal colour boundaries resulted in faster avoidance learning on a multi-coloured background, and predator generalization favoured more internal boundaries, while there was no effect of pattern regularity. From these studies I conclude that internal pattern contrasts may function to increase the efficacy of the warning colour, its salience, and as a means for aposematic prey to be discriminated from harmful mimics. However, the major finding is the importance of colour over pattern.
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| 6. |
- Balogh, Alexandra, 1975-
(author)
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Predator psychology and mimicry evolution - a theoretical analysis
- 2009
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Doctoral thesis (other academic/artistic)abstract
- The evolution of Müllerian mimicry depends on many factors, among which predator psychology is the most important one. Predator avoidance learning, generalization and discrimination are primary selective agents during the evolutionary process. This thesis investigates an issue that has been a matter of debate since the 19th century; the question of how a mutant of a potential mimic population can escape the apostatic selection caused by predators that neither recognize it as a member of its own population, nor as being similar to its future model. In paper I, we investigate one of the ideas concerning this issue. Fisher stated that mimicry can evolve gradually by the displacement of an adaptive peak in a fitness landscape. We find this to be a plausible scenario, under certain conditions regarding predator generalization. In paper II, we further investigate the gradual evolutionary process and the implications of different generalization gradients. We find that the gradual process might be even more general than has previously been assumed and that abundant genetic variation in prey populations is an important factor in combination with predator generalization. In paper III, we examine another suggested solution to the problem of apostatic selection, the so-called two-step process, which can be problematic to extend to multiple prey traits. We find that the two-step process works for multidimensional traits provided that predators use feature-based generalization. The selective landscape of mimicry evolution is also shaped by the cost-benefit relationships for models and mimics. In paper IV we explore this matter, by applying the Rescorla-Wagner theory of learning to mimicry. We find that if variation in prey unpalatability gives rise to surprise, the learning rate is increased. This leads to unexpected kinds of mimicry that are more mutualistic than Müllerian mimicry has previously been assumed to be.
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| 7. |
- Favati, Anna, 1980-
(author)
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Social dominance and personality in male fowl (Gallus gallus domesticus)
- 2013
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Licentiate thesis (other academic/artistic)abstract
- Individuals in social species commonly form dominance relationships among each other, andare often observed to differ in behaviour depending on their social status. However, whethersuch behavioural differences are a consequence of dominance position, or also a cause to it,remains unclear. In this thesis I therefore investigated two perspectives of the relationshipbetween social dominance and personality in the domestic fowl (Gallus gallus domesticus), asocial species that forms relatively stable dominance hierarchies. In paper I I investigated theinfluence of social status on the expression and consistency of behaviours by experimentallychanging status between repeated personality assays. The level of vigilance, activity andexploration changed with social status, while boldness and territorial crows appeared asstable individual properties, independent of status. These results showed that social statuscontribute to both variation and consistency in behavioural responses. Social status shouldtherefore be taken into account when investigating and interpreting variation in personality.In paper II I showed that behaviour in a novel arena test and during encounter with anopponent can predict social status, more specifically that fast exploration and aggressivenesspredicted a dominant social position. Together, these results highlight the dynamics of thetwo-way relationship between social position and individual behaviour and indicate thatindividual behaviour can both be a cause and a consequence of social status.
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| 8. |
- Kazemi, Baharan, 1982-
(author)
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Evolution of Mimicry and Aposematism Explained: Salient Traits and Predator Psychology
- 2017
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Doctoral thesis (other academic/artistic)abstract
- Aposematic species have evolved conspicuous warning signals, such as bright colors and striking patterns, to deter predators. Some edible and harmless species take advantage of this deterrent effect by mimicking their appearance. Mimicry is a great example of how natural selection produces remarkable adaptations. However, while some species evolve a very close similarity to their models to effectively avoid attacks, others are successful in doing so despite an incomplete similarity, i.e. imperfect mimicry. In some cases, it is surprising how such a crude disguise can fool predators. Why and how imperfect mimicry can persist has been much discussed and considered as a problem for the theory of natural selection. It is therefore of great interest to understand what makes it possible.Predator psychology is an important factor in the evolution of aposematism and mimicry. In the past decades it has been suggested that certain components of prey appearance are more important to predators than others during prey assessment. We developed this idea by incorporating concepts from associative learning, and presented a new approach to explain imperfect mimicry. Our general hypothesis is that prey traits have different salience to predators. Certain traits are perceived as highly salient and are thus used primarily in the discrimination and generalization of prey, while traits with low salience are overshadowed and not used in the assessment. The salience of a trait can depend on how conspicuous or discriminable it is in the particular context, and can vary due to for example previous predator experience.We tested our ideas with wild blue tits and domestic chickens as predators, and artificial and semi-natural prey stimuli. In paper I we found that the trait that was perceived as most salient (color) was the one used to discriminate and generalize between prey. Mimics of that specific trait were highly avoided, despite differences in the other traits. We also found that salience is relative and context dependent (paper II). In a context where two traits were perceived as similarly salient, mimicry of a single trait offered intermediate protection, while mimicry of both offered high protection. In another context, the traits were perceived differently salient, and mimicry of one trait was enough for high protection. In paper III we tested a proposed scenario for the initiation of mimicry evolution in the edible butterfly mimic Papilio polyxenes asterius to its noxious model Battus philenor. The results showed that a partial similarity with the model in the salient black wing color offered intermediate protection from attacks, despite a general dissimilarity.This thesis investigates the major questions of imperfect mimicry: the initial step of mimicry evolution, the persistence of imperfect mimicry, and variation in mimic-model similarity. We conclude that mimicry evolution can begin in a non-mimetic species that acquires similarity to a model species in a high-salience trait. When multiple traits have similar salience, multi-trait mimicry is needed for higher protection. Mimicry can remain imperfect if the differences are in traits with low salience, and therefore under low or no selection pressure to change.To complete the picture, we showed that predators can have a biased generalization toward a more pronounced version of a salient trait (paper IV). The evolution of aposematism could therefore be explained by gradual enhancement of salient traits.
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