Global cultural evolutionary model of humpback whale song Zandberg, Lies; Lachlan, Robert F.; Lamoni, Luca ...
Philosophical transactions of the Royal Society of London. Series B. Biological sciences,
10/2021, Letnik:
376, Številka:
1836
Journal Article
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Humpback whale song is an extraordinary example of vocal cultural behaviour. In northern populations, the complex songs show long-lasting traditions that slowly evolve, while in the South Pacific, ...periodic revolutions occur when songs are adopted from neighbouring populations and rapidly spread. In this species, vocal learning cannot be studied in the laboratory, learning is instead inferred from the songs' complexity and patterns of transmission. Here, we used individual-based cultural evolutionary simulations of the entire Southern and Northern Hemisphere humpback whale populations to formalize this process of inference. We modelled processes of song mutation and patterns of contact among populations and compared our model with patterns of song theme sharing measured in South Pacific populations. Low levels of mutation in combination with rare population interactions were sufficient to closely fit the pattern of diversity in the South Pacific, including the distinctive pattern of west-to-east revolutions. Interestingly, the same learning parameters that gave rise to revolutions in the Southern Hemisphere simulations gave rise to evolutionary patterns of cultural evolution in the Northern Hemisphere populations. Our study demonstrates how cultural evolutionary approaches can be used to make inferences about the learning processes underlying cultural transmission and how they might generate emergent population-level processes.
This article is part of the theme issue ‘Vocal learning in animals and humans’.
Quantifying the direction and strength of mate preference is essential to improve our understanding of sexual selection. Experimental designs, however, often do not consider how individuals evaluate ...and compare the available options, which may affect the results significantly. Preferences are often assumed to be absolute, with individuals assigning a fixed, absolute value to a cue or potential partner they encounter. However, individuals may instead also compare the available options, in which case the social context plays an essential role in the preference for each potential partner. Here we investigated the importance of considering the choosers’ evaluation process in mate preference tests. Using a mate preference study on wild great tit, Parus major, heterozygosity, breast stripe size and yellowness as a case study, we tested whether individuals use absolute or comparative mate preferences. We analysed how the perceived average attractiveness and the variation in attractiveness of the group of potential mates affected the measured preference functions. We found that the average attractiveness of the stimulus groups affected the total time individuals spent visiting all stimulus birds, and that the variation in attractiveness within groups affected the measured preference slopes. This indicates that the social context will affect the measured responses to stimulus groups, and that great tits may use both absolute and comparative evaluation. Considering how a study species encounters and evaluates potential mates and how the social environment may affect preferences is essential when choosing an appropriate experimental design to obtain reliable measurements of mate preferences. We therefore strongly advise future studies to consider not only the absolute stimulus trait values, but also the context in which they are presented. The ability to quantify preferences accurately will increase our understanding of mate preferences, mate choice and ultimately sexual selection.
•The choice for a mate is not only made on absolute quality.•The social context affects the choice for a mate.•Individuals can use comparisons between options for their choice.•Birds used a combination of absolute and comparative evaluation of stimulus groups.•How species evaluate mates is crucial for the choice of experimental design.
Under sexual selection, mate preferences can evolve for traits advertising fitness benefits. Observed mating patterns (mate choice) are often assumed to represent preference, even though they result ...from the interaction between preference, sampling strategy and environmental factors. Correlating fitness with mate choice instead of preference will therefore lead to confounded conclusions about the role of preference in sexual selection. Here we show that direct fitness benefits underlie mate preferences for genetic characteristics in a unique experiment on wild great tits. In repeated mate preference tests, both sexes preferred mates that had similar heterozygosity levels to themselves, and not those with which they would optimise offspring heterozygosity. In a subsequent field experiment where we cross fostered offspring, foster parents with more similar heterozygosity levels had higher reproductive success, despite the absence of assortative mating patterns. These results support the idea that selection for preference persists despite constraints on mate choice.
•Personality did not affect the likelihood or latency to solve a foraging task.•Dominant birds were less likely to develop a scrounger tactic.•Fast and slow explorers increased their solving rate ...faster than intermediate birds.•Slow, compared to intermediate and fast explorers obtained the highest payoff.•Personality-dependent variation in problem solving resembles strategy use.
Individuals develop innovative behaviours to solve foraging challenges in the face of changing environmental conditions. Little is known about how individuals differ in their tendency to solve problems and in their subsequent use of this solving behaviour in social contexts. Here we investigated whether individual variation in problem-solving performance could be explained by differences in the likelihood of solving the task, or if they reflect differences in foraging strategy. We tested this by studying the use of a novel foraging skill in groups of great tits (Parus major), consisting of three naive individuals with different personality, and one knowledgeable tutor. We presented them with multiple, identical foraging devices over eight trials. Though birds of different personality type did not differ in solving latency; fast and slow explorers showed a steeper increase over time in their solving rate, compared to intermediate explorers. Despite equal solving potential, personality influenced the subsequent use of the skill, as well as the pay-off received from solving. Thus, variation in the tendency to solve the task reflected differences in foraging strategy among individuals linked to their personality. These results emphasize the importance of considering the social context to fully understand the implications of learning novel skills.
By choosing the right partner individuals can gain reproductive benefits and can increase their reproductive success. These benefits can be direct, when the offspring’s quality or quantity is ...increased by the behaviour or investment of the mate, or indirect, when the quality of the offspring is increased by the genetic contribution of the mate. While previously it was often thought that reproductive benefits were primarily caused by the higher quality of these preferred partners, more and more studies suggest that also partner compatibility may increase reproductive success. Mate compatibility may be especially important when individuals differ in their preferences for a mate. Although uniform preferences are often assumed, an increasing number of studies indicate that individuals have a preference for different trait values (Forstmeier and Birkhead 2004; Lehtonen and Lindström 2008; Holveck and Riebel 2010; Ihle et al. 2015). Moreover, these differences in preference can depend on the chooser’s own trait values (Mays and Hill 2004; Holveck and Riebel 2007). These studies show that individuals may prefer a mate that is the best fit for them, rather than the universally ‘best individual’.A number of studies on captive populations have found that the fitness benefits from mating with a certain individual differ between individuals, suggesting individual differences in preference and both direct and indirect benefits of mating with these compatible mates. However, it is still unclear how compatibility and perceived mate attractiveness affect reproductive success in a wild population. Additionally, to understand fitness consequences and the evolution of mate preferences, preference and choice should be studied as two distinct processes. To our knowledge, no study thus far has combined all three and tested what the fitness benefits of mate preferences are under mate choice constraints in a wild population. Therefore, the overall aim of this thesis was to study the role of individual differences in mate preferences and its effects on reproductive success, by comparing measured mate preference with the resulting choice and relating the pair compatibility with different aspects of reproductive success. When measuring mate preferences results may be affected by how individuals evaluate and compare the available options they are presented with. Preferences are often assumed to be absolute, assigning a fixed, absolute value to a cue or potential partner they encounter. However, in reality, individuals may compare the available options, in which case the social context plays an essential role in the preference for each potential partner. In chapter 2 I used a 6-choice mate choice setup to test great tits for their preferences in a mate. Using such a test design allowed individuals to comparatively evaluate potential partners. Additionally, presenting individuals with 6 choice options allowed for the measurement of non-linear preferences. I reveal that great tits use a combination of both absolute and comparative evaluation and that the social context affected the measured responses to stimulus groups. This suggests that great tits can flexibly use both evaluation methods, depending on the situation they encounter potential mates in. With such knowledge of how a study species encounters and evaluates potential mates, it is possible to choose the most appropriate experimental design and analysis to obtain reliable measurements of mate preferences. The ability to more accurately quantify preference is expected to increase our understanding of mate preferences, mate choice, and ultimately sexual selection. By measuring preferences for traits in a mate I found that individuals differed in their preferences for a mate. In chapter 4 I have found that there were no population-wide mate preferences for the different bird traits that we measured (heterozygosity, intensity yellow breast plumage, black breast stripe size and body condition) and that individual preference slopes for (at least three of) these traits differed between individuals. Thus, rather than preferring the same universally attractive individuals, individuals may prefer a mate that is compatible to themselves. Moreover, individuals may differ in which traits they find important in a mate (chapter 4)Compatibility between pair mates can be dependent on the combination of the pairs’ trait values. In chapter 3 I have shown that preferences for certain traits were dependent on the choosers’ own traits, suggesting preference for compatibility for these traits. By testing individual repeatedly for their mate preferences for genetic characteristics I found that both sexes preferred mates that had heterozygosity levels similar to themselves, and not those with which they would optimise offspring heterozygosity. Moreover, I found that these preferences for similarity in heterozygosity were in reflected in direct benefits for reproductive success. In the subsequent field experiment where we cross fostered offspring, foster parents with more similar heterozygosity levels had higher reproductive success, despite the absence of assortative mating patterns. This suggests that direct fitness benefits underlie mate preferences for genetic characteristics and that the potential for selection for preferences persists despite constraints on mate choice.Another trait that is thought to play a large role in pair compatibility is behavioural compatibility. Especially for species with biparental care behavioural traits, such as personality traits and behavioural compatibility may be important for reproductive success. In chapter 5 I studied the role of personality and behavioural compatibility in the provisioning behaviour in particular, by recording parental provisioning behaviour of great tit pairs with known exploratory behaviour. By experimentally cross-fostering offspring I was able to distinguish between the pre-hatching and rearing effects of parental personality on offspring weight and fledging probability. Here I found that the combination of personalities in a pair did not affect their provisioning behaviour. Instead, I found that although all birds provision on a trade-off between visit rate and prey volume, fast birds brought in smaller prey for a given visit rate resulting in a lower overall amount of prey delivered to their offspring. These differences in provisioning strategy led to faster explorers bringing a lower total prey volume to their offspring. Thus, personality may certainly play a role in direct benefits that individuals gain from finding a mate, however, this benefit was not dependent on the choosers’ own traits. Despite the personality dependent differences in provisioning behaviour, there was no effect of pair compatibility on provisioning performance. However, it is possible that these effects of personality are context dependent, or only become apparent when pairs encounter challenges in their breeding attempt. To gain a better insight into how selection pressures may favour certain combinations of personalities these personality effects should be measured over more different contexts (over different years, different contexts or using experimental manipulations). Additionally, a context dependence of behavioural compatibility suggests a fluctuating selection on personality traits and pair compatibility, and with it a potential for fluctuating selection on preferences for mate personality.Individuals have been shown to have increased reproductive success when they are able to mate with individuals that they perceive as attractive. Since here individuals have been found to differ in their preferences, and some traits can be more or less important for different individuals depending on their own traits (chapter 3 and 4), each individual can differ in how attractive they perceive the same potential mate. This has been shown in captivity where it has been found that the same courter may give higher benefits to some choosers than to others. Here I investigated if the attractiveness of an individual, as perceived by its mate, increased the reproductive success of the pair (chapter 4). On the basis of preference tests I calculated preference functions for each individual and in the subsequent breeding season estimated a measure of how attractive each individual perceived the mate they were paired with. Here I found that while individuals differed in their preference for a mate, they were not more likely to obtain a mate that they perceived as attractive than under random mating. Additionally, I found no effects of perceived mate attractiveness on female reproductive investment, offspring weight or fledging probability. Thus, although with a limited sample size, we found no effect of our measure individual mate attractiveness on reproductive success, this method of estimating preferences and individual mate attractiveness gives the potential for further studies studying pair compatibility and reproductive success. A better understanding of preferences for compatibility rather than quality and the benefits related to this may shed light on the adaptive value of individual differences in preference for mates. By measuring both preference and choice I found that, quite often, preferences are not reflected in the mating patterns that we find in the population (chapter 3 and 4). However, I did find that these preferences were reflected in reproductive benefits (chapter 3). Thus, while not always being able to, those individuals that did find a mate according to their preferences benefitted from compatibility with their mate. Mate choice is therefore the result of choosing a partner according to ones’ preferences whilst under physical and environmental constraints. This emphasizes the importance of measuring both preference and choice to fully understand how sexual selection acts on preferences. To conclude, in this thesis I investigated the role of compatibility on mate
Individuals develop innovative behaviours to solve foraging challenges in the face of changing environmental conditions. Little is known about how individuals differ in their tendency to solve ...problems and in their subsequent use of this solving behaviour in social contexts. Here we investigated whether individual variation in problem-solving performance could be explained by differences in the likelihood of solving the task, or if they reflect differences in foraging strategy. We tested this by studying the use of a novel foraging skill in groups of great tits (Parus major), consisting of three naive individuals with different personality, and one knowledgeable tutor. We presented them with multiple, identical foraging devices over eight trials. Though birds of different personality type did not differ in solving latency; fast and slow explorers showed a steeper increase over time in their solving rate, compared to intermediate explorers. Despite equal solving potential, personality influenced the subsequent use of the skill, as well as the pay-off received from solving. Thus, variation in the tendency to solve the task reflected differences in foraging strategy among individuals linked to their personality. These results emphasize the importance of considering the social context to fully understand the implications of learning novel skills.
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