Chapter 9- Kinship Flashcards
(44 cards)
Parental care
Where one or both parents provide care for their developing offspring
Which species was the first to use parental care?
Waptia fieldensis (a shrimp like species)
Can we use the fossil record to better our understanding of the origin and diversity of parental care?
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.
Why do squirrels display altruistic behavior when it can be risky to an individual?
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.
Inclusive fitness
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.
Altruistic behavior in insects
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.
Kinship
The probability that individuals share copies of alleles that they have inherited from common ancestors, like parents or grandparents
Identical by descent
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
Genetic relatedness (r)
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.
How to calculate genetic relatedness (2)
- Find the most recent common ancestor or ancestors
- 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.
Hamilton’s rule
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
Offspring rule
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
Hamilton’s rule in long tailed tits study
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
Ecological constraints theory
Examines dispersal options of mature offspring and the conditions that favor dispersal from home rather than remaining on natal territory
Reproductive skew theory
Examines how reproductive opportunities are divided among potential breeders by predicting conditions that should favor conflict or cooperation with respect to breeding decisions
Emlen’s components of the evolutionary theory of family dynamics (3)
- Inclusive fitness theory
- Ecological constraints theory
- Reproductive skew theory
Emlen’s prediction regarding family groupings
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.
Nonbreeding groups and inclusive fitness benefits in gorillas
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.
Nonbreeding groups in gorillas
Contains younger males and one older silverback male
Breeding groups in gorillas
Contains one mature male, and adult females and sexually immature males
Family groupings in superb fairy wrens
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
Emlen’s prediction regarding the stability of families based on the quality of resources
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.
Acorn woodpeckers and territory quality study
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
Emlen prediction regarding assistance in rearing offspring
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.
