Lecture 10: Social Behaviours

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Questions and Answers

What is one reason optimal group sizes are often considered a compromise?

Smaller groups promote more individual fitness at the expense of social benefits.

Costs associated with group living can outweigh benefits in larger groups. (correct)

Larger groups always share resources equally.

Optimal group sizes do not impact fitness in any significant way.

Which type of social interaction results in both the donor and recipient increasing their fitness?

Spitefulness

Selfishness

Cooperation (correct)

Altruism

Which of the following statements about altruism is true?

Altruism has no evolutionary advantages.

Altruism leads to a direct increase in the donor's fitness.

All altruistic actions are driven solely by self-preservation.

Altruistic behaviors can enhance fitness of relatives through indirect selection. (correct)

What characterizes the interaction known as spitefulness?

Both donor and recipient suffer a fitness reduction. Signup and view all the answers

How does indirect fitness relate to altruism?

Indirect fitness increases when altruism benefits relatives, enhancing their reproductive success. Signup and view all the answers

What is the indirect fitness calculated for subordinates in wild turkeys using the coefficient of relatedness?

2.6 Signup and view all the answers

In the context of kin selection, how do unrelated females in white-winged trumpeters contribute to raising offspring?

By helping raise offspring without breeding Signup and view all the answers

What is one reason why kin selection isn't the only explanation for cooperative breeding?

Some species thrive in cooperative breeding for survival Signup and view all the answers

What is a characteristic of eusocial species?

Multiple adults live together and cooperate Signup and view all the answers

What happens when a breeding female dies in a group of white-winged trumpeters?

Another unrelated female takes her place Signup and view all the answers

How do plants communicate to warn each other about herbivory?

By releasing chemical signals into the air Signup and view all the answers

What is a social behavior exhibited by free-living slime molds?

They aggregate to form large fruiting bodies Signup and view all the answers

What response do plants exhibit when grown near their relatives?

They develop less dense root masses to minimize competition Signup and view all the answers

What type of behavior does it suggest if plants increase their defenses when nearby plants are attacked?

Altruistic behavior Signup and view all the answers

How do bacteria and protists interact socially?

They secrete chemicals to sense others and react positively or negatively Signup and view all the answers

What is a primary feature of eusocial species?

Reproductive dominance by one or a few individuals Signup and view all the answers

What formula represents the calculation for indirect fitness?

Indirect fitness = B × r Signup and view all the answers

Which caste in eusocial species typically does not reproduce?

Workers Signup and view all the answers

Under what condition is altruism likely to be favored by natural selection?

When the benefit to the relative is high and the donor is closely related to the recipient Signup and view all the answers

What evolutionary advantage does caring for a sister provide to female eusocial insects?

Higher indirect fitness benefit Signup and view all the answers

Which of the following best describes the sex-determination system in hymenopterans?

Haplodiploid where fertilization determines gender Signup and view all the answers

What does the coefficient of relatedness measure?

The probability of any gene being shared by relatives Signup and view all the answers

How do termites differ from hymenopterans in terms of sexuality within the colony?

Termites have no explicit reproductive caste Signup and view all the answers

What is indicated when the cost-benefit ratio (C/TB) is less than the coefficient of relatedness (r)?

Altruistic behavior is favored Signup and view all the answers

What triggers stress in worker mole rats that inhibits their reproductive capabilities?

Harassment from the queen Signup and view all the answers

In the context of kin selection, which of the following is true regarding the indirect fitness?

It is not beneficial to help non-relatives Signup and view all the answers

What is one potential benefit of living in groups related to predator defense?

Reduced probability of being preyed upon Signup and view all the answers

How do groups increase foraging efficiency?

By allowing more individuals to observe and find food Signup and view all the answers

Which characteristic is NOT associated with eusocial species?

Multiple reproductive individuals Signup and view all the answers

Why do subordinate male turkeys display in leks despite not breeding?

To increase their indirect fitness Signup and view all the answers

Which of the following is a cost associated with living in groups?

Higher likelihood of being targeted by predators Signup and view all the answers

Which statement best describes inclusive fitness?

It includes both direct fitness and indirect fitness from relatives Signup and view all the answers

Why might some species exhibit eusociality despite being diploid?

Minimal cost in direct fitness formation Signup and view all the answers

What is a common feature of eusocial species such as bees, wasps, and ants?

A single queen that mates only once Signup and view all the answers

Which equation represents the condition where altruism is favored?

B × r > C Signup and view all the answers

What is a dominance hierarchy?

A ranking system based on individual strength or skill Signup and view all the answers

What semi-permanent area is typically defended by individuals to secure resources?

Territory Signup and view all the answers

What is the common ancestry notion regarding the evolution of eusociality?

Eusociality evolved independently multiple times Signup and view all the answers

Which group size tends to have the lowest stress levels, according to benefits and costs of living in groups?

50-75 individuals Signup and view all the answers

Eusocial species demonstrate extreme social interactions. Which is NOT a characteristic of eusocial species?

Isolation until maturity Signup and view all the answers

What is the primary role of lekking behavior in group living?

For attracting potential mates Signup and view all the answers

In which scenario is the dilution effect primarily beneficial?

When in a predator-rich environment Signup and view all the answers

Natural selection favors group sizes that:

Balance the costs and benefits Signup and view all the answers

Study Notes

Social behaviours are individual interactions with mates, offspring, relatives, and unrelated conspecifics.
These behaviours are shaped by genetic and environmental factors.
Social behaviours are subject to natural selection.
Social behaviours are usually associated with mate selection or intraspecific competition for food or territory.
Social interactions have both costs and benefits.

Benefits of Living in Groups

Living in groups can increase survival.
Groups of individuals can more effectively fend off attacks from predators.
The dilution effect reduces the probability of predation for individuals in a group.
Increased vigilance, such as that seen in meerkats, also aids survival by allowing the group to be better at detecting threats.
Grouping can improve foraging success by providing more eyes to locate and consume resources.
Larger numbers of conspecifics improve the chances of finding food.
Groups can increase the likelihood of capturing prey.
Grouping can make it easier to find mates, especially in species that use leks.

Increased Vigilance

Individuals in groups may decrease the amount of time spent watching for predators, and increase the time spent feeding.
This is demonstrated by the European goldfinch.

Costs of Living in Groups

Living in groups increases competition for food.
Larger groups may be better at finding food, but more individuals mean food must be shared.
High population densities can increase the spread of disease and parasitism.
Groups of animals are more conspicuous to predators.
This is demonstrated by studying parasitism in coral reef fish.

Balancing Costs and Benefits

Natural selection favours group sizes that balance the costs and benefits for each species.
Medium-sized groups often have the lowest stress levels due to reduced competition for resources and better ability to fend off other groups/predators.
Yellow baboons are a good example, with group sizes typically ranging from 20 to 100 individuals.

Many Species Establish Territories

A territory is an area defended by one or more individuals.
Territories typically contain resources such as food and limited nest sites.
Defending a territory may allow for access to greater resources and potentially more mates.
Roe deer are an example of a species that establishes territories.

Dominance Hierarchies

When benefits of group living outweigh the benefits of defending a territory, species often form dominance hierarchies, establishing social ranking among individuals.
Dominance hierarchies are often determined through contests of strength or skill.
Once established, subsequent disputes are typically resolved by the dominance ranking.

Eusocial Species

Eusocial species exhibit social interactions to the extreme, displaying several characteristics.
These include overlapping generations of parents and offspring living together in the same group.
Cooperation in nest building and brood care is characteristic of these species.
Reproductive dominance by one or a few individuals, and the presence of sterile individuals, is observed.
Almost all eusocial species are insects, including termites, bees, wasps, and ants.
Two mammals are eusocial species: the naked mole rat and the Damaraland mole rat.
Most individuals in eusocial species do not sexually mature and instead specialize in tasks, known as castes.

Eusociality in Ants, Bees, and Wasps

Eusociality is common in Hymenopterans (ants, bees, wasps).
The society is typically dominated by one or more egg-laying females, referred to as queens.
Fertile females produce a large number of offspring, even potentially more than a million offspring over a 10–15 year period.
Non-reproductive offspring gather food and care for the young.
The queen has the same relatedness to sons/daughters (r = 0.5).
All females have the same genes from their father.
All females retain 50% probability of shared genes from their mothers (r = 0.75).
Brother-sister relatedness is r=0.25.

Eusociality in Termites

Termites are diploid insects that have a different evolutionary history compared to hymenopterans.
Colonies are dominated by one king and queen and produce sons and daughters via sexual reproduction.
Offspring act as workers, and can become sexually mature if the king/queen dies.
Soldiers are members of a second non-reproductive caste.

Eusociality in Mole Rats

Social mole rats live in colonies of up to 200 individuals.
Reproduction is managed by a single queen and multiple kings.
All individuals are diploid.
Workers are capable of reproduction but are often harassed and stressed by the queen, leading to reduced sex hormones and an inhibition of reproductive drive.

Origins of Eusociality

Eusociality evolved independently multiple times.
Haplodiploidy seems to favour eusociality, but some haplodiploid species are not eusocial, and some eusocial species are diploid.
Eusociality could be due to minimal costs in direct fitness, though this is debatable.

Many species besides animals exhibit social behaviour.
Even bacteria and protists can sense and react to other individuals via chemical secretions, potentially exhibiting aggressive or friendly interactions.
Free-living slime molds aggregate to form large fruiting bodies.
Plants communicate chemically with one another.

Plants can warn other plants about herbivory.
E.g., Alder trees are known to warn nearby plants about herbivory when their leaves are consumed and releases chemicals when attacked by herbivores.
Nearby plants detect these chemicals and increase their defences.
This behaviour is not necessarily considered a social behaviour as the mechanisms are unknown.

Plants can distinguish between relatives and non-relatives.
When grown near relatives, plants often develop less dense root mass due to less competition.
When grown near non-relatives, plants often develop a denser root mass, indicating higher levels of competition.

Additional Information

The lecture's learning objectives include describing how living in groups has costs and benefits, explaining the four types of social interactions in animals, and explaining how eusocial species exhibit social interactions to an extreme.
A concept check in the lecture asked students to identify how the dilution effect is a benefit of group-living.
A second concept check asked students to explain how optimal group sizes represent a compromise between the costs and benefits of group living, and provide at least one example.
Another check asked students to explain why altruism cannot be fully explained by direct fitness alone.

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Description

Explore the intricacies of social behaviours in various species, focusing on interactions among mates, offspring, and rivals. Understand how genetic and environmental factors shape these behaviours and their implications for survival and natural selection. This quiz will challenge your knowledge of the benefits and costs associated with living in groups.