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Date Created: 04/20/16
L10 Notes: I. Population Models A. Evolutionary Stable Strategies 1. What is best for an individual may not be best for an entire group? a. Therefore the payoff for performing a behavior may depend on what others are doing in the same population b. Nash Equilibrium i. First described by John Nash ii. Subject of the movie (a beautiful mind) 2. Evolutionary Stable Strategy (ESS) a. A strategy which when adopted by most members of a population cannot be beaten by any other strategy in the game b. Pure strategy: each individual plays only one strategy all the time (ALLD) c. Mixed strategy: individuals may play different strategies at different times (ex. TFT) 3. A question to ponder: should I stay or should I go? a. As the cow pat dries out, fewer females of flies come to pat b. As a result, more males leave and fewer stay c. However, those that do stay longer have the same mating success as those who leaves early B. Ideal Free Distribution (IFD) 1. Individuals should always select the best habitat available 2. As more individuals enter habitat quality decreases due to competition for resources 3. All individuals have equally reduced quality habitats R rich rich Rpoor Npoor 4. Resources available in each patch are always equal to the R/N where: a. R = # of resources in a patch b. N = # of individuals in a patch c. Eventually the value of each patch becomes equal to one another 5. Assumptions: a. Resources are distributed in patches b. Competitors are equal in all respects c. Competitors may switch patches d. Competitors have complete knowledge e. Resource density remains constant f. Intake rate increases with resource density and decreases with computer density 6. Ducks: ducks also distribute themselves according to the predictions of the IFD C. Ideal Despotic Distribution (IDD) 1. First individuals in a territory defend the resource excluding others, later individuals must accept lower quality territories and less resources a. All competitors are never equal b. Patches are never shared c. Patch values are usually never equal d. Sometimes not everyone gets a patch 2. IDD Assumptions a. Resources are distributed in patches b. Competitors are unequal in their ability to exploit resources c. Competitors may switch patches d. Competitors have complete knowledge e. Resource density remains constant f. Intake rate increases with resource density and decreases with competitor density 3. Ex. Aphids a. Position near stem has highest value decreases in value is due to resource access b. Larger leaves as more resources and are chosen first c. Optimal leaf choice depends on both leave size and number on leaf D. Economic Dependability 1. When should an individual defend a territory vs. share a territory? a. when the benefits of extra resources is greater than the cost of territory defense 2. ex. Pied wagtails a. territorial male defending territory b. territorial male sharing with satellite male c. satellite males not chased when availability is high but the addition or deletion of food resulted in change of behavior as predicted by the model of pied wagtails 3. ex. Sideblotched lizards a. when rocks were removed, territorial defense present, no sharing b. when rocks were added, territorial defense is absent, favorable to sharing 4. ex. rufous hummingbirds a. weight gain was low when too few or too many flowers were in the territory b. weight gain was highest with intermediate flower density 5. ex. Gray wolves in Yellowstone a. is pack size optimized for efficient hunting or for efficient territory defense? i. Pack size varies with: Age range of members Proximity to the next pack Number of prey in territory ii. Pack longevity varies with: Age (experiences) of leaders Stability of social structure Pack size Pack longevity is positively related to pack size rather than location of territory or availability of prey iii. Pack success varies with Number of offspring that survive Ability to hold territory across generations Ability to defend borders from rival packs II. GamesTheory Model A. HawkDove Model 1. Hawk Strategy a. Always fight to injure and kill opponent 2. Dove strategy a. Always display, but do not fight 3. Pay off: a. Winner gains (V) b. Loser gains (0) 4. Cost a. Fighting loss costs (C) b. Display loss costs (0) 5. 6. If you meet a predator once, you want to be Dove but if you meet it many times you should be hawk 7. Ex. Speckled wood butterfly a. Territory owners wins most fights b. If intruder is allowed to become territory owner, new owner (former intruder) now wins suggest strategy is conditional, not fixed B. Producer Scrounger Model 1. Producer strategy a. Always seeks food by active hunting 2. Scrounger strategy a. Always steal food discovered by others 3. Both strategies fitness declines with density 4. ESS is the proportion of scroungers where producer and scrounger fitness is equal III. Habitat Selection A. Habitat Preferences 1. How do individuals come to recognize suitable habitats? 2. Innate settlement cues a. Red algae extract conch b. Wave sounds reef fish 3. Learn cues from natal habitat a. Butterflies (feed on plant as larvae, lay eggs on that same plant) b. Salmon (odor cues to their native stream) c. Artic terns (come back to the locations of where they were hatched) 4. Use conspecifics as settlement cues a. Barnacles use smell cue to choose habitat b. Lizards use other lizards (need smell to choose habitat) c. Songbirds B. Ecological Traps 1. What if the cues that used to indicate quality habitat no longer do so? a. Historically cues indicate high quality habitat b. Due to rapid degradation of habitat, cues no longer are associated with quality habitats c. This can arise when the original environment is replaced by a new environment d. This can also arise when the new environment happens to have a very similar cue to the original 2. Ecological traps are over estimates of habitat quality 3. Underestimates of habitat quality may be just as bad 4. Conservation biologists might solve this problem by improving habitat or introducing the proper cue I. Play A. Activities that appear purposeless in which motor patterns in which motor patterns from other contexts may often be used in modified form and altered temporal sequencing B. Types of Play 1. Object play: use of an object beyond that of trying to determine what the object is 2. Locomotor play: run around; rapid sequencing of movement of speeds and postures 3. Social play: coordinate behaviors develop social skills C. General Theory of Play 1. Play may be adaptive if it trains specific motorsocial skills that may be essential later in life 2. Aids in cognitive development 3. Prepares animals for life 4. Predictions: a. Physiological challenges of unexpected events involving loss of control b. Individuals with more play should do better in loss of control situations c. Dominant individuals should allow subordinates to defeat them during play d. Behavior should activate motor, somatosensory, and emotional areas of the brain e. Play should be most common in species that experience variable environments D. Acquisition of Play 1. Hormones mediate play: testosterone stimulates play fighting while dopamine prepares the brain for play 2. Neural centers for play: parafascicular area (PFA) is involved along with the fosc gene (epigenetic control; need to know play to be able to play) II. Personality A. What maintains distinct behavioral phenotypes in a population? 1. ESS favors equal proportion of producers and scroungers B. Definitions of Personality 1. Consistent: longterm phenotypic behavioral response of an individual across different situations a. Behavioral type b. Coping styles c. Personality 2. Opposite of behavioral plasticity: ability of an organism to behave differently depending on environmental conditions C. Personality (Behavioral) Types 1. More broad the personality spectrum, the more variable the environment is 2. BoldShy Axis 3. a. Indicates the type of behavior that is present in individuals in a population 4. Behavioral Correlation Across Situations a. Same context, but different situations and describes the fixed behavior phenotype of the response of an individual to a stimuli. b. Consistent behavioral response usually correlates with distinct behavioral types D. ProactiveReactive Axis 1. Proactiverun away; Proactive: grab predator E. Behavioral Syndromes 1. A suite of correlated behaviors reflecting between individual consistency in behavior across multiple situations a. Individuals have behavior types (bold, shy, passive, aggressive, active, inactive, reactive, proactive) b. Populations have behavioral syndromes 2. Principle Component Analysis (PCA) a. Based on a certain stimuli/response, indicates the response and whether that is a certain personality type 3. Ex. Great Tits a. “Fast Birds” aggressive, approach novel objects, quickly approach members of the opposite sex b. “Slow Birds” nonaggressive, avoid novel objects, slowly approach members of the opposite sex c. Differ in their exploratory behaviors and the two sexes are under directional selection forces and is stabilizing. I. Ecology of Communication A. Types of Information 1. Personal Info (Observations): personally acquired; information about physical habitat, resource availability, number of competitors (Knowledge) 2. Social Info (Cues): inadvertently acquired; information about location of resources or the quality of resources based on the preferences of others (Public Info) 3. Social Info (Signals): intentionally acquired information shared with others that due to natural selection contains honest information regarding one’s state, intentions, size, quality, or abilities (Communication) 4. How do ordinary behaviors become signals? a. Intention movements b. Ambivalent behavior c. Protective responses d. Autonomic responses e. Displacement activities f. Redirected attacks B. Channels 1. Communication may be more or less effective depending on the limitations on the channel 2. Multimodal signals are those that employ multiple channels at the same time 3. Important signals often involve sequential assessments 4. These often utilize different channels of communication to increase effectiveness 5. Ex. Elk usually use olfactory, auditory, visual, and tactile channels C. Categories 1. Categories describe the context of the information 2. The amount of information and the specificity of the signal increases with each category 3. Interspecific (sexual interspecific the most complex) 4. Nonsexual intraspecific 5. 6. Ex. Tungara frogs: sometimes add extra syllables to their advertisement calls because the extra syllables are more attractive to females, however, they are also more attractive to bad predators a. Solution: make extra chucks only when they are in large choruses and are harder to pick out by bad predators II. Evolution of Communication A. Signal Reliability 1. Communication is an evolutionary arms race where senders try to manipulate receivers and receivers try to mindread senders 2. If senders manipulate receivers too well, then receivers will be favored to ignore senders 3. So signals must carry information of interest to the receiver that convey a benefit on average 4. So what maintains the honesty of signals? Indices B. Indices 1. Indices are honest signals because their production is limited by physical attributes that cannot be faked 2. Sequential assessments make good indices 3. Usually size determines how many assessments are needed to determine a winner a. Big size differences are usually determined by tail beating (in certain fish) b. Small size differences usually lead to through all four assessments and is determined by circling (in certain fish) 4. Ex. Frog calls a. The frequency of a frog call is inversely proportional to its size b. The decision to try and displace a mating male frog was shown to be influenced by whether the call was high or deep c. However, large males were still challenged less than small males 5. Ex. Elk bugle a. Frequency of elk bugle is proportional to body size b. Thus, the bugle can signal size and predict reproductive success C. Handicaps 1. Handicaps are honest signals because they are costly to produce 2. Lowquality males cannot afford to produce these high cost signals but high quality males can a. If the benefit (B) of producing a costly ornament is equal for all males and the cost (C) producing the ornament is less in high quality males than in low quality males then the signal is a reliable indicator of male quality because only high quality males are selected to produce the signal b. Ex. Wasp faces i. When wasp faces were manipulated by adding or removing black dots ii. There was no change in the behavior of the manipulated wasp iii. But their opponent would increase aggression toward them D. Common Interests 1. Sender and receiver have a common interest, such that there is no benefit to deceiving the receiver (ex. Mate recognition signals )
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