Evolutionary Ecology

Front 1

Who is Thomas Malthus and what effect did he have on Darwin's theory?

Back 1

Developed theory of population growth based on carrying capacity.
Darwin realized that competition and conflict are what drives natural selection and that this is most prominent among members of a species
However, cooperation is also seen: among cells and organs, between mates in act of sexual reproduction, among social species, and between mutualistic pairs of species

Front 2

Explain what brood parasitism is.

Back 2

Brood parasitism occurs in bird species where females lay eggs in other nests.
Obligate: lay eggs in nests of other species. These species have completely lost ability to construct nests and incubate eggs.
Non-obligate: lay eggs in nests of conspecifics and in their own nests.
• "Host" birds have learned to differentiate to some degree between their eggs and "parasite" eggs. Color variation ranked from 1 to 7, color rank difference of 2 is sufficient for host to reject parasitic eggs.

Front 3

Explain the conflict between individual and group benefit as seen in slime mold.

Back 3

Individual cells form a moving organism when resources are scarce. Spore forming cells reproduce while stalk-forming cells die. "Cheater" mutations have arisen that preferentially make spores. These mutant cells cause wild-type cells to move to the front to form the stalk

Front 4

Is it individually advantageous not to escalate conflicts?

Back 4

Aggressive encounters seldom escalate into physical conflicts/death.

Front 5

Explain the assessor strategy.

Back 5

Individual escalates conflict if it judges opponent to be smaller/weaker but retreats if opponent is larger/stronger
• Many animals react aggressively independent of the opponents correlated features.

Front 6

What are honest and dishonest signals?

Back 6

Honest signals: indicate individual's fighting ability or resource-holding potential
ex. Anolis dewlap size correlated with force of bite
Dishonest signals: deceptive signals that indicate greater fighting ability than the individual actually has. Rare.

Front 7

Define cooperation

Back 7

Activity that provide a benefit to other individuals and to the actor

Front 8

Define altruism

Back 8

Activity that proves a benefit to other individuals but poses a risk/harm to actor

Front 9

What are direct and delayed benefits of cooperation?

Back 9

Direct: individual in a herd has a lower risk of predation
Delayed: ex. of manakins: females prefer teams so 2 + males will do a dance to attract her, but the dominant male obtains all/almost all copulations. Subordinate male succeeds when dominant dies, but this can take up to 13 years

Front 10

Define reciprocity

Back 10

Cooperation based on repeated interactions. An individual may profit from benefiting another if there is a high likelihood that he will reciprocate in the future.
However, it is possible that the individual will defect and a price was paid for no compensation

Front 11

Explain how punishment of noncooperators works in reciprocity.

Back 11

Cooperation is enhanced in reciprocity if selfish "cheaters" are punished because punishment alters the ratio of benefit to cost
Ex. Legumes: provide photosynthate for rhizobia bacteria who fix Nitrogen. Rhizobia can cheat by receiving the photosynthate and not fixing nitrogen, but legumes impose sanction by limiting supply of oxygen against poorly performing nodules

Front 12

Explain kin selection

Back 12

An altruistic gene can spread by natural selection if causes discrimination against kin and non-kin since relatives are genetically similar, a gene that causes the propagation of copies of itself will be fixed more readily.

Front 13

Explain Hamilton's rule.

Back 13

States that an altruistic trait can increase in frequency if the benefit received by donor's relatives, weighted by relationship to donor, exceeds the cost to the donor.
So altruism spreads if rb > c
Haldane: I would lay down my life for 2 brothers or 8 cousins

Front 14

Explain kin recognition.

Back 14

For kin selection to work, individuals need to distinguish related individuals from unrelated ones. Ants, for example, have distinctive colony order that allows this. If individuals are usually associated with kin such as primates and prairie dogs that live in colonies or troops mostly composed of relatives, this is not necessary

Front 15

Explain the green-beard model.

Back 15

The bearer of an allele for altruism can recognize other individuals that carry the same allele, whether or not they are closely related. This causes 3 phenotypic effects: 1. a perceptive trait (hypothetical green beard) 2. Recognition of this trait in others 3. Preferential treatment for those recognized
Ex. cSA gene in slime mold encodes a cell adhesion protein that binds to the protein in the membrane of other cells. Cells unrelated will not be allowed to form the slug

Front 16

Explain promiscuous mating

Back 16

2 types
1. Polygyny: male mates promiscuously
2. Polyandry: female mates with multiple partners

Front 17

Explain the dynamics in a monogamous pair bond.

Back 17

Females in some pair-bonding species favor males with characteristics that serve as honest signals of paternal caregiving such as the brightness of the male's breast or larger repertoire of songs
Selection favors defection more strongly in the sex in which parental care is more costly: meaning one parent will give less care than the other.
ex. Male fish often mate with multiple females and guard all their eggs in a single nest: males pay smaller cost than females, who have to use up a lot of resources and energy in making eggs.
ex. Birds and mammals feed their young: parental care is more costly for males, since males could obtain many matings in the time it takes to rear one brood.

Front 18

What is eusociality?

Back 18

The most extreme form of altruism: Naked mole rats, all termites, and in Hymnoptera: ants and bees
Evolved independently many times
In insects: female workers that do not mate while Queens lay eggs that develop into either workers or reproductive females and males. Haplodiploid, meaning females develop from fertilized eggs and are diploid while males are from unfertilized eggs so they are haploid. So they have different relativity ratios than usual. A female is more related to her sister than to her daughter

Front 19

Define genetic conflict.

Back 19

Mitochondrial/cytoplasmatically inherited genes often conflict with nuclear genes. They can exaggerate sexual conflict because they benefit from enhancing female, but not male fitness

Front 20

What is an example of genetic conflict?

Back 20

In humans: mother increases insulin production during pregnancy which removes glucose from blood but the fetus produces high levels of a hormone that counteracts this so there is no net alteration of blood glucose concentration int the blood. This seems to serve no purpose, but makes sense since offspring want more resources from the mother than the mother is willing to give, since she wants to reserve some for potential future offspring.

Front 21

Define horizontal transmission

Back 21

Endosymbionts are transmitted laterally among members of the host population. Selection favors symbiont genotypes with high reproductive rate, even if host is killed
Selection favors evolution of a parasite

Front 22

Define vertical transmission

Back 22

Endosymbionts are transmitted from mother host to daughter host.
Consequence: reproductive success of the endosymbiont depends entirely on fitness of the host
Selection favors genotypes with restrained reproduction that do not cause the death of host before it can transmit it to its progeny. It also favors alleles that will enhance the fitness of the host, since it also enhances fitness of the symbiont. This can lead to evolution of mutualism