Evolution Exam 4

Provide an evolutionary explanation for the sex difference in alarm calling frequency observed in Beldings's ground squirrel populations.

- Alarm calls are mostly emitted by females

What is an "alliance"? Describe the types of alliances that exist in dolphin herding behavior.

- Alliance: when coalitions exist for a long period of time - First order alliance: composed of pairs or trios of males acting in a coordinated fashion to keep females by their side for purpose of mating - Second order alliance: when they aggressively attack and steal females from other alliances

Genetic models have shown that large-scale changes in the genome (i.e. genetic revolutions") are unlikely and unnecessary for divergence & speciation to occur. Summarize experimental evidence in support of this notion. Be specific.

- An experiment conducted with the three spine stickleback was done to distinguish between closely-related species - Marine tickles are larger in size and freshwaters tickles have longer spines and more numerous boney lateral plates - Tests show that limnetic and benthic species mate assortatively and that hybrids between the two have lower fitness than either parent

Summarize byproduct mutualism and provide an example.

- Byproduct mutualism: cooperation is a byproduct of the fact that an individual would incur an immediate cost/penalty if it did not act cooperatively ex/ house sparrow food calls - House sparrows produce a unique "chirrup" call when they come upon a food source - This call attracts other birds to the newly discovered food and this is considered as some type of cooperation - Call rates were higher when food resource was divisible

How might communal nesting female mice be "cheated" by other females in the group? How do they solve this problem? Include in your answer an evolutionary explanation for WHY this would likely solve the problem.

- Communal nesting can create a situation in which the females are cheated because other females at their nest are protected from danger, but don't nurse all the pups present - One way to get around this is to form communal nests with their genetic relatives

Animals that are not genetic relatives cooperate with each other in many contexts. How can such cooperative behavior emerge among animals in the absence of kin selection? Describe/discuss three proposed explanations for the evolution and maintenance of such cooperative behavior among animals.

- Cooperation occurs in many contexts such as foraging, predation, anti-predator behaviors, mating, play aggressive interaction, etc. 1) Reciprocity 2) Byproduct mutualism 3) Group selection

What are cryptic species?

- Cryptic species: groups that were/are actually independent of one another, but appear to be members of the same species based on morphological similarity

Describe "first-order" and second order" alliances in dolphins. What are their primary functions? Is this kind of cooperation common across the animal kingdom? Explain.

- Described in last flashcard - Primary functions consist of ganging up on females for mating purposes or stealing females from others - This kind of cooperation is common in many primate species as well as hyenas, wolves, cheetahs, and of course dolphins

Distinguish between dyadic and polyadic interactions.

- Dyadic: two individuals interact in such a way that the fitness of each is affected by both its own action and the action of its partner - Polyadic: interactions that involve more than two individuals

Given the power of kinship to affect social interactions, how do kin recognize one another? Can they calculate genetic relatedness? Explain.

- Each sibling values the other at a level that is half of that at which it values itself - NS individuals who act in a manner that makes it appear as though they are making calculations for genetic relatedness - Kin recognize each other through complex vocal cues and vocal signatures emitted by young ex/ species in emperor and king pernguins

Trivers addressed the evolution of reciprocal altruism using game theory. What is game theory and how did Trivers use it to explain the evolution of cooperative behavior in animals?

- Game theory: math tool used when the payoff an individual receives for undertaking an action is dependent on what behaviors others adopt - Trivers uses this to explain the evolution of cooperative behavior in animals by employing the game, "prisoner's dilemma"

What advantage do specialist species have over generalist species? What advantage to generalists have over specialists?

- Generalist species can live in many different places, eat a variety of foods, tolerate a wide range of environmental conditions - Specialist species can specialize more and there will not be overlap and there are fewer competitors

Genetic drift has long been hypothesized as "the key to speciation's second stage". Provide a theoretical explanation for why this was believed to be the case.

- Genetic drift can cause random fixation of alleles and random loss of alleles - It is a sampling process and its effects will be most pronounced in small populations - As it continues to occur in the small, derived population, it leads to a random loss of alleles and the random fixation of both existing and new alleles

What is "hybrid inferiority"? Explain how it serves as a form of post-mating reproductive isolation.

- Hybrid inferiority: when hybrids are not well adapted to the environment

Summarize the basic premise of the "rule of thumb" model of kin recognition. Provide some "pros" and "cons" of using such a kin recognition strategy.

- If it lives in your nest/cave/territory, then treat it like kin - NS should favor this - This rule can also be subject to cheating

A parent could "dispense every ounce of energy it has to provide offspring X with all the benefits at its disposal". Make a case for why natural selection should or should not favor such a parental strategy.

- If such an effort kills the parent or severely hampers the parent from producing other offspring in the future, than NS may not favor such behavior

Human babies weighing over 9 lbs are at greater risk of developing gestational diabetes as adults. Given what we have learned in class about the condition and its development, how might we explain the statistic above? Hint: Start by addressing the question of how babies might get so big before birth.

- If there are higher blood glucose levels in the mother, the baby will gain extra glucose and this will cause it to be put on extra weight - Since that extra glucose was brought to them as fetuses, this may affect their bodies when they grow after birth

The parent-offspring conflict predicted in any population is in part a function of the mating system that exists in that population. Explain and provide an example to illustrate your point.

- In long-term monogamous species, current offspring will have an average genetic relatedness of 0.5 because they're likely to have the same mother and father - In polyandrous species where a female mates with several males, NS will favor offspring who attempt to extract more in the way of parental assistance since genetic relatedness of current and future offspring will be somewhere between 0.25 and 0.5

Can inclusive fitness theory be used to understand conflicts within families? Explain.

- Inclusive fitness theory can be used to understand conflicts within families - This is because it predicts that parents should go to great lengths to help their offspring because parents and offspring have an average "r" of 0.5 - This creates strong selection pressure for parents to provide aid to their offspring

Define "inclusive fitness" and Hamilton's rule and provide an example.

- Inclusive fitness: if a gene codes for preferentially aiding genetic kin, then that gene can increase its representation in the next generation because it is coding for aid to individuals that are likely to have "G" as well - Hamilton's Rule: the essence of inclusive fitness models is that they consider the effect of a gene, not only on the individual in which it resides, but on individuals carrying genes that are identical by descent

Summarize the "matching model" of kin recognition. How are such internal templates generated? Provide some hypothetical examples of how they might form.

- Individual 1 determines if individual 2 is kin or nankin, depending on how closely individual 2 matches the internal template of individual 1 - This internal template may be generated genetically via learning or social learning

What is gestational diabetes? Is it a disease? How might we explain this condition for the perspective of evolutionary medicine?

- It is a possible outcome of parent-offspring conflict - Doctors view it as an evolutionary measure selected by fetal genes to increase sugar flow to the fetus

Why is sexual selection considered a particularly effective process in producing speciation?

- It results from differences among individuals in their ability to attract mates - In Hawaiian Drosophila, it is thought to be a key factor in promoting divergence among isolated pops. - 2 populations diverge due to sexual selection

Why would an alarm caller do anything to attract a predator in its direction and make itself the predator's most likely next meal?

- Its genetic relatedness can affect its behavior in many important ways - This plays a large role in whether or not a squirrel will emit an alarm call when a predator is detected

Compare and contrast the morphospecies concept, the biological species concept, and the phylogenetic species concept. What criteria does each use to identify species? What are the pros and cons of each?

- Morphospecies concept: identifying species is done when distinguishing between difference in color or soft tissue; advantage is that these species can be identified in organisms that are extinct or living, sexual and asexual; disadvantage is some species can be difficult to apply in groups like Bacteria, Archaea, and many fungi that are small and have few measurable morphological traits to assess - Biological species concept: identifying species is done through reproductive isolation; advantage is that reproductive isolation confirms lack of gene flow; disadvantage is that this concept is difficult to apply because if nearby populations do not overlap, researchers have no way of knowing whether they're reproductively isolated - Phylogenetic species concept: identifying species is done through estimating phylogeny of closely-related populations and finding the smallest monophyletic groups; advantage is that it can applied to any type of organism (sexually reproducing, asexual, or fossil); disadvantage is that populations must have been evolutionary independent long enough for the diagnostic traits to have evolved

Describe/compare kin recognition in nest-building penguins vs. those that rear their young in dense colonies with no nests (e.g. emperor penguins). Discuss how natural selection for kin recognition has operated differently on the two.

- Parents can find their offspring y remembering the location of their nests - NS to recognize offspring by vocal cues in these species is weak - When the kin recognition is more difficult, NS favors the evolution of more complex vocal recognition systems

Describe the "parent-offspring conflict" that occurs between a women and her developing fetus during pregnancy (be specific). Explain the costs and benefits to the fetus and Mom.

- Placentally produced hormones change the uterus environment in a manner that benefits the fetus at the cost of the mother - A fetus may use human placental lactose to manipulate insulin in such a manner that sugar remains in the blood a longer time than normal which provides the fetus with more time to access the sugar - The maternal-counter response is to increase insulin production and if this is unsuccessful, the fetus can obtain extra sugar, but the mother suffers from gestational diabetes

Distinguish between pre- and postzygotic isolation. State and describe the 4 forms of reproductive isolation which prevent/avoid the needless loss of gametes (eggs & sperm).

- Prezygotic isolation: divergence in traits which prevents fertilization from occurring - Postzygotic isolation: when populations also remain genetically isolated in the absence of reinforcement if hybrid offspring are sterile or infertile 1) Gamete mortality: male mates with female, but sperm dies in female reproductive trait 2) Zygote mortality 3) Hybrid inferiority: hybrids are not well adapted to environment 4) Hybrid sterility: hybrids don't have proper functioning reproductive organs

Define "reciprocal altruism"

- Reciprocal altruism: exchanging acts of cooperative and altruistic behavior

What is reinforcement? Summarize "the logic" behind it. What does the reinforcement hypothesis predict about secondary contact between previously isolated populations?

- Reinforcement: when selection reduces the frequency of hybrids - The hypothesis states that when closely-related species come in contact and hybridize, a mechanism that prevents hybridization will evolve

Discuss sibling rivalry in resource poor vs. resource rich environments.

- Resource poor: intense, lethal competition would emerge among the siblings - Resource rich: interactions would be less competitive since more food is added

Can spatial cues and kin recognition rules change through the lifetime of an individual? Explain and provide an example. Why might natural selection favor such a switch?

- Spatial cues and kin recognition rules can change through the lifetime of an individual - ex/ bank swallows - When their chicks are about 20 days old, mothers witch from their rule of thumb to using distinctive vocal cues in order to recognize and feed their offspring

Summarize the tit-for-tat (TFT) "solution" to the iterated prisoner's dilemma game. Explain the role of social learning in this solution.

- TFT: strategy in which an individual cooperates on the first encounter with a partner and subsequently copies its partner's move - If the individual is nice, they will never cheat first - If the individual is forgiving, they will forgive earlier cheating - If the individual is retaliatory, they will see cheating and cheat as well

Summarize the allopatic model of speciation. Explain the difference between dispersal and vicariance. Why might dispersal or vicariance events initiate speciation? Describe examples of species that are hypothesized to have speciated by vicariance and dispersal.

- The allopathic model of speciation shows that physical isolation creates an effective barrier to gene flow - Dispersal or vicariance events can initiate speciation due to situations where an existing range is split by a new physical barrier - Lizards are a good example of a species that can be speciated by vicariance and dispersal

House sparrows produce a unique "chirrup" call when they come upon a food source. Explain why this serves as an example of animal cooperation. Furthermore, provide an explanation for the evolution of such cooperative behavior. Summarize the evidence (research on sparrow behavior) supporting your explanation from a cost/benefit perspective.

- The chirrup calls may be regarded as some type of cooperation because they attract other birds to the newly discovered food - Those arriving to the food were most likely to produce the chirrup calls - The hypothesis is that if food items were small enough that sparrows could pick them up and fly away, they'd go without producing chirrup calls - Byproduct mutualism comes into play when calls are emitted when the immediate net benefit for calling is greater than the net benefit for not calling

Summarize the prisoner's dilemma game (include in your answer a description of the alternative strategies and payoff matrix). What exactly IS the "dilemma" here? Is there an ESS in an iterated version of the game? Explain.

- The game is comprised of two criminal suspects interrogated by police in hope of getting a confession from one or both of them - Defect: "The other suspect is guilty officer!" - Cooperate: "I have no idea what you're talking about. We're both innocent!" - Payoff matrix: 1) R = reward for mutual cooperation = 1 yr in jail 2) P = punishment for mutual defection = 3 yrs in jail 3) T = temptation for cheat payoff = 0 yrs in jail 4) S = sucker's payoff = 5 yrs in jail - The actual dilemma is T > R > P > S - There is an ESS in an iterated version of the game called the TFT strategy

How might MHC genes be used in kin recognition? Discuss empirical evidence that such a mechanism exists in animals (be specific).

- The genes are used to ID by an odor when determining a mate to choose - In mice, females can discriminate among kin and nonkin through odors associated with the MHC genes

Describe the evolutionary arms race that occurs between nest parasites such as cowbirds and their hosts.

- The kin recognition rule is subject to cheating - The nest parasites can cause the cowbirds to "forget" about some of their offspring

The "b" & "c" terms of Hamilton's model are particularly difficult to measure in nature. How have Ethologists solved this problem? Explain with an example.

- They have solved this problem with the offspring rule which uses the number of offspring that were born and survived as the currency of measure - It sets up the possibility of field manipulations in which Hamilton's ideas could be tested by counting the number of offspring across different experimental treatments ex/ if an ethologist wants to know the positive effects that young "helps-at-the-nest" might have on raising their siblings, they could examine the difference in the average number of chicks that survive in the presence or absence of "helpers"

What does it mean to say that species are "evolutionarily independent"?

- This is used when something occurs when mutation, NS, gene flow, and drift operate on populations separately

When the Panama land bridge between North & South America was uncovered, some N. American mammal lineages crossed to South America and underwent dramatic radiations. For terrestrial species, did the completion of the land bridge represent a vicariance or dispersal event? Why? Does the recent building of the Panama Canal represent a vicariance or dispersal event for terrestrial organisms? For marine organisms? Explain your answers.

- This represented a vicariance event because the populations that were sampled appeared to represent 7 pairs of closely related species pairs with one member of each pair found on each side of the land bridge and the phylogeny of the shrimp also explains why - Both terrestrial and marine organisms were also known to have represented a vicariance event because vicariance has been an important isolating mechanism and trigger for speciation in a wide variety of groups

Explain the evolutionary significance of Rieseberg's studies of sunflowers in the American Southwest.

- This study shows if hybrid populations will occupy a new environment and become a distinct species - The experimental and natural hybrids were genetically almost identical

Morphologically similar species of snapping shrimp that are each other's closet relatives live on either side of the Isthmus of Panama. Does this observation support the hypothesis that speciation occurred via vicariance or colonization? Explain your answer.

- This supports the hypothesis that speciation occurred via vicariance because when they put males and females of vicarious species pairs together, and watched or aggressive and pairing interactions, they found a strong correlation between the degree of genetic distance between species pairs and how interested the shrimper in courting

Summarize Robert Trivers' parent-offspring conflict theory.

- When parents must make decisions regarding how much aid to give any particular offspring - These decisions are affected by: 1) how much energy is available for helping current offspring 2) how many offspring it is likely to have in the future

Distinguish between "within-group" and "between-group" selection with respect to animal cooperation.

- Within-group selection: acts against cooperators and altruists; selfish types are always favored since they receive any benefits that accrue because o the actions of cooperators, but pay no cost - between group selection: favors cooperation if groups with more cooperators out-produce other groups

Explain (in evolutionary terms) the "zone of conflict" between Mom and offspring X with regard to parental care.

- Zone of conflict: between how much offspring X wants a parent to give him/her and how much a parent is willing to give

Define the terms "r", "b", "A" and "c" in Hamilton's inclusive fitness model. How does each variable impact the decision to aid family members?

- r = our measure of relatedness - b = the benefit that others receive - A = number of individuals affected by the trait of interest - c = the cost accrued to the individual expressing the trait - The decision to aid family members is a function of: 1) how related individuals are 2) how high or low the costs and benefits associated with the trait turn out to be

Is it possible for speciation to occur in the absence of physical isolation between populations? If so, explain one mechanism for how it may occur.

- yes, one way is through tetraploid population which is created by mutation that produces diploid gametes - If they mate with members of the diploid population, homologues do not pair properly at meiosis, leading to cells with dysfunctional chromosome complements

At least 8 geographically-isolated populations of spiny lizard exist in the mountains and deserts of north & central Mexico. Although females look similar, males in each population are strikingly different - ranging from black to gold to green, orange, and blue. An analysis has shown that at least 5 of the populations are phylogenetic species. Would they be considered species under the morphospecies and biological species concepts as well? Researchers suggest that sexual selection has been responsible for speciation in this group. Outline a study that would test this hypothesis.

- you have to test on whether these species can interbreed - Pair males and females from different pops. and see if they mate - If they do mate from different pops., then this means that the females are willing to choose different mates from a different pop. - evolutionary independent long enough to develop traits of sister pairs - identify derived traits that make up phylogenetic species - morphospecies concept involves physical character traits in comparing different populations - Conduct a mate choice study; see if females mate assortatively in their own population whether they choose the males or not - Hybrid vs. Purebred - No gene flow if they hybridize (not separate species)

What are the possible outcomes when species that have long been separated geographically come back into contact and begin hybridizing? Under what conditions does each outcome occur?

1) Equal to parent form: higher frequencies of hybrid individuals are found and decrease with increasing distance; the conditions that cause this to occur is the length of the hybrid zone and the distance of dispersal of individuals from each population in each generation 2) Lower than parents form: short-lived and narrower; strength of selection determines this outcome 3) Higher than parent form: reinforcement occurs and new species is formed; hybrid zone is dependent on whether positive fitness advantage occurs in new habitat or ecotone

Using our hypothetical "lizard island" example discussed in class, explain the classic 3-stage speciation process and how adaptation to local conditions can lead to speciation.

1) Isolation of populations 2) Divergence in traits 3) Reproductive Isolation - The isolation and divergence steps were thought to take place over time and to occur while pops. were located in different geographic areas

A parent's decision regarding how much aid to give any particular offspring is a function of . . .

Parent-offspring Conflict

Do placentally produced hormones change the in utero environment in a manner that benefits the fetus at the cost of the mother? Explain.

Yes because the mother can suffer from gestational diabetes

Provide an example of how group selection might operate in favor of cooperation.

ex/ Alarm calls: groups with many alarm callers may out-produce groups with fewer cooperators - For such groups, benefits to be manifest, groups must differ in the frequency of cooperators within them