Behavioral Ecology Flashcards
The science of the ultimate, evolutionary causes for behavior.
It brings together three sciences; ecology, animal behavior, and evolutionary biology.
Behavioral Ecology
Natural selection acts on _____. The result is to produce _____ which is adaptive and enables the organism to survive and reproduce in its current environment.
Behavior
The philosophical position that organisms, over time, should have developed behavior that maximizes their fitness
Optimality
The so called “optimal” behavior needed to maximize inclusive fitness will depend on 2 things
Behavior of other individuals
Ecological circumstances
Natural selection should cause adaptive behavior to evolve, but will behaviors always be optimal? List the 5 possible obstacles
Variation Pleiotropy Variable Environments Evolutionary Lag Phylogenetic Inertia
Obstacle that many mutations produce individuals with lower fitness, and populations will be expected to have genetic and environmental variation.
Variation
Obstacle that alleles have multiple effects. So, if an allele influences traits X, Y, & Z, with X being an optimum phenotype, there’s no reason to assume Y & Z are also optimum
Pleiotropy
Obstacle that a behavior that is optimal in one environment may not be so in other environments, and allele flow might interfere with the evolution of behaviors that are locally optimal.
Variable Environments
Obstacle that individuals adapted to past conditions are not necessarily adapted to present conditions
Evolutionary Lag
Obstacle of an organisms prior evolutionary history
Phylogenetic inertia
comparing species in divergent lineages, to see if there is a pattern of convergent evolution, where lineages that enter particular ecological niches evolve certain behaviors or structures, is widely used in evolutionary biology.
The comparative method
By comparing different species, behavioral ecologists can link behavior and social organization to ecological factors.
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It is important to find pairs or clusters of species that have independently evolved in response to their environment, and not simply inherited both their behavior and their ecology from a common ancestor.
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John Allman hypothesized that the polymorphism in life history between males and females was related to…
Parental care
For males in species where males provide parental care, increased or decreased life span is supported?
Increased
The major criticism of optimality models is that they appear to test the animal to see whether it is behaving perfectly according to the model.
It is important not to loose sight of the fact that the model is being tested, not the animal.
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The inherent assumption of optimality theory, that animals behave in a way that maximizes their fitness, is not likely to be met all the time.
Thus, if the animal’s behavior does not match the model, is the animal flawed or is it the model?
One of the best approaches is to see whether animals that behave according to the model have higher fitness than animals that deviate from it.
One of the most interesting things about natural selection for a behavior is that the behaviors of other individuals in the populations may affect the fitness of an individual.
Some behaviors, such as stealing from another individual’s nest, may be favored by selection when they are uncommon (thieves are rare and the population is naïve). When they become common, however, they may be selected against (in a population where everyone is stealing from everyone else, there is nothing left to steal)
the modeling of outcomes when two or more players adopt stragegies (behaviors) which affect each others payoffs (fitness).
Axelrod, Hamilton, and John Maynard Smith brought it to behavioral ecology
Ecological Game theory
A species example of ecological game theory, it is a close relative of the species Fabre studied.
It digs a burrow in the ground and stocks it with paralyzed crickets.
Digger Wasps
It’s easier to take over a burrow if more wasps are building them and less are taking them over, but as the behavior becomes more common, disadvantages accumulate
Ecological Game Theory and Digger Wasps
What does ecological game theory predict regarding digger wasps?
The two behaviors should be balanced in the population by natural selection so that they have equal fitness
If one of the differ wasp behaviors has a higher fitness, what happens to it?
It becomes more common until its fitness drops to equal the other one
What conclusion did Brockmann and Grafen come to regarding the wasp behavior over several seasons?
The two strategies have roughly equal fitness, even though wasps have the capacity to do them both
Behavior that increases the fitness of another individual at the expense of one’s own fitness.
Altruism
Who are the most conspicuously selfless animals?
Social Insects like ants, bees, wasps.
-work for the good of the colony and don’t reproduce themselves
W.D. Hamilton argued that altruism can evolve if individuals increase their ___________ , that is, the proportion of their genes carried by others in the population by acting altruistically
Inclusive Fitness
Some behaviors have evolved to increase the fitness of an organism’s close relatives.
Individuals with certain heritable traits might have genotypes that code for behaviors that help close relatives raise more offspring than they would without help.
These alleles would be favored by a broader form selection…aka
Kin Selection
Provided that their close relatives are likely to have copies of the same heritable traits, an allele can spread even if it decreases the direct fitness of an individual bearing it, provided that the total copies of the gene increase, as a result of the bearer’s actions.
! Kin Selection
A behavior that helps a close relative’s fitness, even though it harms one’s own fitness, should be expected to evolve provided that: Br>C
Hamilton’s Rule
____ is the benefit to the relative in terms of increased fitness
_____ is the coefficient of relatedness
______ is the cost of that behavior in terms of one’s own fitness
B
r
C
the probability that a particular allele, present in one individual, is also present in another individulal because of descent form a common ancestor.
Relatedness
The mathematical expression of the probability of relatedness
r
This is a function of one’s behavior on their own survival and reproduction, as well as the effect of one’s behavior on all relatives (with the importance of each relative valued in proportion to degree of relatedness).
Inclusive fitness
In this type of insect Any female has the potential to be a queen, though those born at the end of the year are larger and more dominant.
Small females born in the middle of the summer are always workers, though one of them will potentially take over if the queen dies.
Polistes sp., a genus of paper wasps
These large females of polistes sp. mate and overwinter. In spring, they emerge and;
- found their own nests
- join females that have already founded
Females that “join” usually get bullied into the subordinate, worker role.
Thus, their personal fitness is close to zero (they occasionally sneak a few of their own eggs in).
Thus, C is the number of offspring their colony would have produced if they did not join another female’s nest.
In the worker role, they increase their own inclusive fitness by helping the queen.
Nests with multiple foundresses are more likely to survive and produce more males and potential queens at the end of the year (fitness for a colony of social insects must be measured by counting males and queens, since workers do not reproduce their genes).
Thus, B is the increased number of offspring a colony will have when it has the extra foundress.
Should unrelated females work together?
No. There is no benefit to the female who does not become queen. (r=0)
Wasps have a special genetic system, so that sisters are particularly closely related. r between wasp sisters is between .75 and .50, depending upon whether they share the same father.
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Do studies of Polistes support Hamilton’s rule?
Yes
- Unrelated sisters do not generally cooperate (at least not after the issue of who will become queen is settled)
- Lone females have a low chance of colony survival.
- The first female who joins her sisters and acts as a “worker” definitely increases the chance of colony survivorship (thus, B is greater than zero).
Observations supporting Hamilton’s rule
It is tough to measure B exactly, and one of the reasons females join is to possibly take over the nest from the female who founded it, thus there is an element of game theory to the system.
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Accounting for the fact that the female that looses the battle would have very low fitness if she went off on her own, because she would be a late-starter (thus, C is small), Br>C.
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Do extra helpers after the first joiner in polistes help the colony more or less?
Less. Thus, B is low for the second joiner, lower still for the third joiner
How many polistes females do you typically see working together in North America?
You rarely see more than two.
In environments where there is competition for nest sites, or colony founding is particularly dangerous, will queens work together more or less?
More. because B is larger (reflecting the extra need for help) and C (reflecting the smaller sacrifice in fitness because going it alone is so risky) is smaller.
Thus, several Mischocyttarus (Caribbean species) females work together, and hundreds of Polybia (closely related genus, Central American) females may work together to found a nest.
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How does an organism ‘know’ its relatives (and, if known or recognized, the degree of relatedness)?
In some cases, the biology of the organism facilitates close relatives living in close proximity.
In other cases, there are mechanisms of kin recognition.
Kin recognition is sometimes accomplished by smell, sometimes it is a function of cognition and memory, sometimes it is biochemical.
What do social insects, like polistes generally use?
Smell, they have a colony odor
recognize each other by chemical signals (MHC genes, the same chemicals that enable our bodies to reject foreign organs) on their skin. Kin colonies of tunicates grow together. Non-kin colonies form a “zone of death” between each other
Tunicates
