Chapter 9- Kinship

Question 1

Parental care

Answer 1

Where one or both parents provide care for their developing offspring

Question 2

Which species was the first to use parental care?

Answer 2

Waptia fieldensis (a shrimp like species)

Question 3

Can we use the fossil record to better our understanding of the origin and diversity of parental care?

Answer 3

Fossils from multiple locations were examined for evidence of brood care. Brood care was found in multiple species from 450-500 million years ago. At least 3 different brood care strategies were uncovered.

Question 4

Why do squirrels display altruistic behavior when it can be risky to an individual?

Answer 4

A (usually female) squirrel will emit an alarm call when it sees a predator, even though an alarm call can be dangerous to the squirrel that emits it. It has been found that genetic relatedness play a role in how natural selection favors alarm calls. In Belding’s ground squirrels, males leave their group to find mates, but females live their entire lives in their natal area. This means that females are among genetic relatives while adult males are usually in groups without genetic relatives. Therefore, females are warning genetic relatives using alarm calls. When moved to a new group without genetic relatives, females will emit less alarm calls.

Question 5

Inclusive fitness

Answer 5

A measure of an individual’s total fitness based on both the number of its own offspring and the contribution it makes to the reproductive success of its genetic relatives. The social behavior of a species evolves in a way that the individual will value its neighbors’ fitness against its own based on the relationship to the individual and the situation. An allele will be able to increase its representation in the next generation if it codes for preferentially aiding genetic kin- it codes for aid for individuals who are likely to have a copy of that allele that is identical by descent.

Question 6

Altruistic behavior in insects

Answer 6

Darwin was one of the first to suggest that suicidally altruistic behavior he observed in social insects like bees could have evolved as a result of bees defending hives filled with their relatives. If the recipients of an altruistic act are relatives, natural selection could favor altruism.

Question 7

Kinship

Answer 7

The probability that individuals share copies of alleles that they have inherited from common ancestors, like parents or grandparents

Question 8

Identical by descent

Answer 8

Alleles that are shared because of common ancestry are referred to as identical by descent. The most recent common ancestors are those through which two or more organisms can trace alleles they share by descent. You share some of the same alleles with your siblings because your most recent common ancestor is your parents, and you share some of the same alleles with your cousins because your most recent common ancestor is your grandparents

Question 9

Genetic relatedness (r)

Answer 9

The probability that two or more individuals with a common ancestor share alleles that are identical by descent. Two siblings would have an r value of .5. That is because there are only two ways that siblings can share a copy of an allele. There is a 50% chance that one parent passed an allele to an offspring. Therefore, there is a 25% chance that both siblings share that specific allele through that parent. To determine the probability that both siblings share the allele through either parent, we add the percentages to get 50%. The r value for cousins is .125 (1/8) and the r value for grandparents and grandchildren and for aunts/uncles with nieces and nephews is .25.

Question 10

How to calculate genetic relatedness (2)

Answer 10

1. Find the most recent common ancestor or ancestors
2. Compute the probabilities that a given allele copy in each ancestor is passed to each offspring. Multiple these percentages to get the r value for the probability for both offspring.

Question 11

Hamilton’s rule

Answer 11

Predicts when a allele that is associated with a trait will increase in frequency. Considers the r value, the count of individuals affected by the trait, the cost accrued by the individual expressing the trait, and the benefit that others receive from the trait in question. This is related to indirect fitness. A high genetic relatedness and benefit will make the trait more frequent. Also, as the number of relatives helped by an act of altruism increases, selection more strongly favors altruism. However, some of these variables are difficult to measure in nature

Question 12

Offspring rule

Answer 12

Used the number of offspring that were born and survived as a measure of benefit/cost in Hamilton’s rule. This formulation could be used in field studies by comparing the average number of offspring that survive in one condition vs another

Question 13

Hamilton’s rule in long tailed tits study

Answer 13

Long tailed tit breeders who lost their nest to predation will join another nest and help breeders in the nest raise their young. Focused on male breeders, since males tend to remain in their natal areas. Researchers studied whether joining nests to help created benefits and relatedness exceeding costs for the helpers. An r value was .2 was found between helpers and the breeders they assisted, and an r value of .16 was found between helpers and the chicks they helped. They then measured benefits received by helpers, looking at recruitment rate (the increased probability that chicks who are helped survive their first year make it to the breeding population the next year), as well as the increased survival of male breeders who helped. The r times b value was found to be greater than c

Question 14

Ecological constraints theory

Answer 14

Examines dispersal options of mature offspring and the conditions that favor dispersal from home rather than remaining on natal territory

Question 15

Reproductive skew theory

Answer 15

Examines how reproductive opportunities are divided among potential breeders by predicting conditions that should favor conflict or cooperation with respect to breeding decisions

Question 16

Emlen’s components of the evolutionary theory of family dynamics (3)

Answer 16

1. Inclusive fitness theory
2. Ecological constraints theory
3. Reproductive skew theory

Question 17

Emlen’s prediction regarding family groupings

Answer 17

Emlen predicted that family groupings would be unstable, and that groupings would dissolve when other reproductive opportunities came up. It was hypothesized that individuals who have a higher inclusive fitness should stay as part of a family unit, but they should leave if there are better fitness opportunities elsewhere. This prediction can be examined by creating new, unoccupied territories and examining whether mature offspring leave their natal area to live in the new areas.

Question 18

Nonbreeding groups and inclusive fitness benefits in gorillas

Answer 18

Male western lowland gorillas may be found in one or more social conditions- a solitary male, a member of a nonbreeding group (NBG), and a member of a breeding group (BG). Males can shift from being solitary to being part of an NBG or BG. Researchers examined whether there were inclusive fitness benefits associated with being part of an NBG for immature males or for the single male silverback. There was no evidence that males preferentially joined groups in which other nonbreeding males were their relatives. However, males showed a strong preference for joining NBGs with a silverback male, since these groups tend to be safer and associated with more food. Among NBGs that contained a silverback, males preferred to join groups where they were related to the silverback. Therefore, silverbacks receive indirect benefits where they protect their genetic relatives that will go on to form their own breeding groups. The inclusive benefits for young males joining an NBG group with a related silverback are unclear.

Question 19

Nonbreeding groups in gorillas

Answer 19

Contains younger males and one older silverback male

Question 20

Breeding groups in gorillas

Answer 20

Contains one mature male, and adult females and sexually immature males

Question 21

Family groupings in superb fairy wrens

Answer 21

In this species, a breeding pair is often helped by its nonbreeding young male offspring, who will provide siblings with food and protection. Researchers wanted to test the prediction that families will break down when suitable territories emerge for younger males, so they removed the breeding males from 29 female territories- after this happened, all but one of the male helpers moved to a new territory. This is likely because a shortage of females and breeding territories created an environment where reproductive opportunities were rare, so male helpers took the new opportunity and left their family. Helping at a nest might raise inclusive fitness of young males when territories are limited, but not otherwise. However, as a whole, data does not support Emlen’s prediction. In humans, married couples stay in contact with their parents as much as single individuals, suggesting that marriage does not dissolve family units

Question 22

Emlen’s prediction regarding the stability of families based on the quality of resources

Answer 22

Predicted that families that control high quality resources will be more stable than those with lower quality resources, and that families in a resource rich area will tend to stay in the same area under generations. Inclusive fitness theory predicts that individuals will remain in their natal territory if there are enough resources for them to mate and provide for their own offspring. Data from bird species indicated that birds from high quality family territories are actually less likely to disperse from their natal territory than those from inferior areas.

Question 23

Acorn woodpeckers and territory quality study

Answer 23

In acorn woodpeckers, the number of storage holes is a measure of territory quality. Individuals on territories with many storage holes produced a greater average number of offspring. In areas with a greater number of holes, more offspring stayed in their natal territories than in areas with less holes. In high quality territories, males that served as helpers had a high probability of entering the breeding population, and breeding in their natal area. Data suggest that contact and support are found more often in wealthy families in humans, supporting the idea that families with more resources are more stable

Question 24

Emlen prediction regarding assistance in rearing offspring

Answer 24

Predicted that assistance in rearing offspring (cooperative breeding) would be expressed more often between family members that are the closest genetic relatives. Inclusive fitness theory suggests that all else being equal, when given the choice between helping individuals that differ with respect to r, more aid should be dispensed to the closest genetic kin than to more distantly related kin.

Question 25

White fronted bee eater birds kinship

Answer 25

Helpers in this species frequently chose to aid individuals they were most closely related to. Altmann had proposed the all or nothing model, where an individual would dispense all of its aid to the recipient that is its closest genetic relative. This study found that the model was accurate- helpers overwhelmingly chose to help their closest genetic relative, and dispensed all of their aid to the chosen individual

Question 26

Haplodiploid species

Answer 26

Males in the species are haploid while females are diploid. Haplodiploidy produces sisters that are on average more related to each other than in more classical diploid animal systems (r= .75), so females are more related to their sisters than to their offspring. Full sisters inherit exactly the same alleles from their father. Found most commonly in eusocial insects. Haplodiploidy alone does not explain the evolution of eusociality, but it helps explain why eusociality is overrepresented in social hymenopterans (bees, ants, wasps)

Question 27

High genetic relatedness and eusociality study in bees

Answer 27

Genetic relatedness is highest in social insect groups when queens are monandrous (have a single mate). Therefore, researchers predicted that eusociality in bees should be associated with a monogamous mating system. A phylogenetic analysis indicated that monandry was the ancestral state in all eusocial lineages examined

Question 28

Worker policing in honeybees

Answer 28

When workers bees use information associated with genetic relatedness to police their hive, and destroy eggs that have low genetic relatedness to them. This results in an increase in their inclusive fitness. Workers seem to use an egg marking pheromone produced only by queens to distinguish which eggs to destroy

Question 29

Genetic relatedness in honeybees

Answer 29

Queens produce most of the offspring, but workers can produce unfertilized eggs that always develop into males. In honeybee colonies with a single queen that mates once, female workers are more related to their nephews than to their brothers. However, honeybee queens typically mate 10-20 times, so workers are more closely related to brothers (produced by queen) than to nephews (produced by sister workers). Worker policing may evolve in this situation.

Question 30

Kinship and reproduction in honeybees

Answer 30

If policing is effective at removing eggs laid by workers, it was hypothesized that it should produce strong selection pressure against worker reproduction. It was found that the more effective policing was at removing worker eggs, the less often workers attempted to reproduce in the first place

Question 31

Parent-offspring conflict

Answer 31

Inclusive fitness theory predicts that parents should help their offspring (because r= .5). Parents are also usually in a better position to help offspring than vice versa. A parent’s decision to help is based on how much energy they have and how many offspring it’s likely to have in the future. Natural selection might not favor the parent using all of its energy when it might not maximize the total number of offspring produced.

Question 32

Parental investment

Answer 32

An offspring will receive some inclusive fitness benefits when its parent provides aid to siblings. Siblings have an r value of .5, but one offspring as an r value of 1 since it’s completely related to itself. Therefore, an offspring benefits more by receiving a parent’s aid themselves. A parent benefits equally regardless of which offspring it helps, so there is a conflict between what the offspring wants and how much the parent can give

Question 33

Why is the degree of relatedness between current and future offspring a function of the mating system?

Answer 33

In species with long term monogamy, current and future offspring will be related by a value of .5 because they will likely have the same mother and father. In systems like polyandry, the r value will range between .25 and .5 due to half siblings. In polyandrous mating systems, natural selection will favor offspring that attempt to extract more in the way of parental assistance. Therefore, parent-offspring conflict would be more intense in a polyandrous vs monogamous mating system.

Question 34

Parent-offspring conflict in polyandrous vs monogamous mating systems study

Answer 34

Parent offspring conflict begins in utero, where the mother generally has the upper hand. However, the fetus can’t be deprived of resources without also depriving the mother. Researchers used an independent contrast phylogenetic method and predicted that in polyandrous mating systems, a fetus would attempt to sequester more resources during development and would have a faster rate of growth than fetuses in species that are monogamous. The results revealed that this relationship does exist

Question 35

Relationship between testes size and polyandry

Answer 35

Sperm competition is more intense in polyandrous species, so males in these species tend to have larger testes. Testes size can therefore be used as a proxy for the degree of polyandry. It was found that there is a positive relationship between testes size and parent-offspring conflict

Question 36

In utero conflict in humans

Answer 36

Fetal cells invade the maternal endometrium (membrane lining the uterus) during implantation, the cells manipulate the maternal spiral arteries in a way that would make them difficult to constrict. Constriction would make fewer resources available to the fetus. This action benefits the fetus by providing the fetus with direct access to maternal arterial blood and allowing the fetus to release hormones and other substances directly into the maternal bloodstream. It also puts the volume of blood and the nutrients it contains under fetal, rather than maternal, control

Question 37

How can fetuses manipulate human placental lactogen?

Answer 37

A fetus can use human placental lactogen to manipulate insulin so that sugar would remain in the blood longer than normal. This provides the fetus with more time to access sugar for itself, but increases production of insulin in the mother. If this countermeasure is unsuccessful, the mother will experience gestational diabetes. Gestational diabetes can be viewed as a disease or as an evolutionary measure to increase sugar flow to the fetus

Question 38

Sibling rivalry

Answer 38

What helps one sibling is usually helpful for the other sibling- kin selection theory predicts that individuals shouldn’t be aggressive to kin like siblings. However, in situations where resources are limited and the siblings have to compete, each sibling wants those resources for themselves

Question 39

Sibling rivalry in egrets

Answer 39

Egret siblings often fight viciously, which can even result in the death of less dominant chicks. Parents provide enough food when egret chicks first hatch, but there is less food for the chicks as they grow. Egrets hatch eggs in sequence rather than all at once, so there are chicks who differ in age by many days. The chicks that hatch first start to feed sooner and receive more food, so they have a weight advantage over chicks that hatch later. Large size means better fighting ability, which translates into more food

Question 40

How do penguins identify their offspring?

Answer 40

Penguins travel long distances to find food and bring it back to their colony. There are often many other chicks in the colony, so penguins recognize their kin using vocal signatures that are emitted by the young. Penguins that live in dense colonies are more adept at recognizing the vocal cues because it is favored by natural selection when penguins are unable to remember the location of their nests

Question 41

Kin recognition matching models

Answer 41

Models of kin recognition that hypothesize that individuals have an “internal template” against which they match others and gauge relatedness. The internal template can be generated genetically, via learning, or via social learning, but the animal estimates the degree of kinship as some function of the extent to which others match its own template. Some templates can only distinguish between kin and non kin, but others can determine which type of relative an individual is

Question 42

Template matching in spadefoot toad tadpoles

Answer 42

There are 2 feeding morphs of spadefoot toads- juveniles that feed on detritus will morph into herbivorous omnivores, while those that feed on shrimp tend to mature into carnivorous cannibals. Researchers tested both morphs in the presence of either unfamiliar siblings or unfamiliar nonrelatives. When visual cues (behavior, morphology) and chemical cues (odors) were present, herbivores preferred associating with their siblings over unrelated individuals. Carnivorous individuals spent more time near unrelated individuals, probably to avoid the costs of killing their genetic kin. When allowed to eat tadpoles, the carnivorous individuals were able to distinguish between related and nonrelated individuals and ate nonrelated individuals much more frequently. However, the toads were less picky when they had been starved for 24 hours, and they would eat genetic kin in this situation

Question 43

Major histocompatibility complex and kin recognition

Answer 43

Researchers examined MHC in house mice, where females nest together and nurse all offspring at their nest- this is beneficial because it protects offspring against infanticidal males. The problem is that females can be “cheated” in a communal nest, where females are protected from danger but don’t nurse all of the offspring present. However, forming communal nests with genetic relatives can minimize the cheater problem while maximizing inclusive fitness benefits. Females can identify relatives using odor cues to determine an individual’s MHC. One study found that females tended to choose a communal nest based on whether it contained individuals with MHC complexes similar to their own.

Question 44

Social learning and kinship in Siberian jays

Answer 44

Siberian jays live in groups made up of adults and their offspring, plus unrelated young migrants who join the group. Hawks and owls are the main predators in this population, and when a perched predator is observed, adults will emit mobbing calls. Researchers hypothesized that all young would copy the antipredator behavior of adults, and that kinship wouldn’t affect the role that social learning might have on antipredator behavior in young Siberian jays. A covered model predator was placed on a pole close to a feeding station where jays fed, and it was uncovered when they got close. Contrary to the hypothesis, it was found that kinship played a significant role in social learning and mobbing behavior. Related young followed their parents and copied their mobbing calls, while unrelated individuals behaved very differently