Competition II Flashcards
What is direct competition? What is a form of direct competition not yet discussed? What is territoriality typically accompanied by?
- Competition directly by fighting.
- Competing by setting up territories and defending against intruders (territoriality)
- Asymmetry between individuals (differences in ability to fight and defend territories)
What is a general idea talked about in relation to direct competition and territoriality? What are its three outcomes? What is this called?
- Two habitat model (poor and rich)
- 1) Rich contains most competitive individuals. 2) Poor = lower quality individuals 3) Lowest quality roam without setting up a territory
- Ideal Despotic Distribution
What are two distributions when talking about competition?
Ideal free and ideal despotic
What is an example of the Ideal Despotic Distribution? Elaborate. What is an important note about this system?
- great tits in Wytham woods vs crop field hedge rows
High quality = Wytham woods (oak woodland, completely fills in spring)
Low quality = hedge rows in crop fields (woods that outline fields, less food/breeding success)
Removing birds in Wytham leads to quickly-filled spots by great tits in the hedge rows
Note: Hedgerows are monitoring territory in the woods.
What is a second example of the IDD?
- Red grouse in the heather moors
What is one problem between the IDD and IFD? What is an example that demonstrates this problem? Elaborate on the example. What were its three conclusions? How does this support the IDD?
- The IDD can look like IFD if the little guys fill in where the big guys are done (such as if despots just take more without chasing out the little guys non-despots)
- Aphids on cottonwood - thought to follow the free. Females –> galls –> babies in gall –> quantity/quality of phloem from leaf determines reproductive success. Large leaves = increased phloem but increased galls = bad (so a growing population on a large leaf doesn’t help). So! High quality habitat is established near the leaf base to get more from tree (as opposed to being further up the leaf which is farther from the flow)
- 1) Bigger leaf = increase in reproductive success. 2) success decreases with # moms/galls. 3) No diff. in average success for 1/2/3 mothers
4) The third conclusion supports the ideal free (all individuals are equally well) BUT this is NOT the case because aphids fill the gap when a mom leaves the high quality habitat (suggesting a high quality mom getting the spot, and IDD).
How does territory size relate to economic defendability? Describe the curves for both poor and rich territories to be smaller, and explain why these curve look that way.
- Larger the territory = harder/more energy to defend
- a) Rich smaller than poor -
rich benefit curve is steeper, rich benefit curve asymptotes at smaller territory sizes
The gains stay consistent at smaller territories but as it gets larger the benefits stop coming as fast
b) poor smaller than rich -
rich benefit curve increases then abruptly stops, poor benefit curve increases at a steady rate, and cost curve increases quickly exponentially, if both are linear (This was not explained in lecture, good luck)
What is the general idea between territory size and economic defendability? What is an example in Indiana? What was the behavior observed in each habitat?
- Cost to defend = higher than benefits (resources) then no territoriality
- Stephens woods vs Ross Reserve and chickadees/titmice. Stephens = cut and replaced with walnuts (bad for small birds - nuts too big). Ross = untouched for 75 years
- Stephens: 2-5x larger territory, forage over an undefined territory
Ross: defend small territories
What are the two circumstances where animals should not be territorial?
- If cost of defending exceeds resource benefits
- Resources are abundant (surplus = enough for everyone so no fitness advantage to fight others over it) (may not be defensible b/c of excessive # intruders such as fish schools)
When can social defendability occur (a circumstance of territoriality defined by social constructs instead of economic decisions)? What is an example? Under what circumstance is a satellite allowed? What are the two ways satellites help the owner? Who proved that this is all true for wagtails?
- Territoriality is allowed when a single individual is incapable of defending a resource.
- Pied wagtails - feed on insects washed on the riverbank so sets up a trap line that it goes around every 40 minutes (to ensure insect buildup for food).
- When food arrival rates are high (leading to high intruder rates) b/c satellites will help reduce defending time for owner.
- Chasing intruders away (reducing defense time for owner) and halving cycle time (reducing ability for intruder to sneak in)
- Davies and Houston using open/closed circle graphs (closed = use satellites)
What is the single gradient of male responses when it comes to settling into a territory?
Take the best habitat you can when you settle (whether finding the best or filling a gap when a high quality leaves/dies)
What is one foraging tactic aside from IDD/IFD? What are two examples of this tactic? What multiple foraging techniques are used by ruddy turnstones? How are these important?
- Producer/scrounger - producers find food and scroungers steal food from producers
- 1) Arabian babblers 2)Spice finches
- Stone turning/digging/routing (dominant)/ surface pecking/hammering barnacles/ probing
- Remove doms, some subs increase routing and some keep their behaviors, suggesting that behavior choice is not frequency dependent.
What are two ways that producer/scrounger can be maintained in the population? How is fitness of each individual impacted in each way?
- Producers are high quality individuals, so scroungers are “making the best of a bad job”
Producers = always higher fitness curve and fitness of both decreases as scroungers increase (less food)
- Relative payoff is frequency depending leading to a stable ESS (one has increased fitness with many of the other)
Elaborate on the spice finches example of producer/scrounger foraging technique. What were the two conditions of the experiment? What were the results of each?
6 finches:
three on producer side (pull a string to feed the scrounger but their food came through a hole)
three on scrounger side (waited for producers to pull the string then ate food)
Two treatments:
Dishes uncovered and dishes covered (harder for scroungers to get seeds)
- 1) Birds cannot choose their side and 2) birds can choose their side
- 1) Payoffs were frequency dependent and feeding rate of scroungers decreased with covered dishes
2) Went into a stable ESS dependent on frequency dependent payoffs
What is the difference between a tactic and strategy? What is a multi-tactic strategy and what are its conditions?
- Strategy - genetically based decision rule (result of different alleles)
Tactic - specific behavior pattern played as part of a strategy (single unconditional behavior)
- Many tactics for one strategy; choice of behavior is conditional on a factor
What is an example of conditional strategies with alternative mating tactics? Elaborate. What is the role of the small-called male? What is this role dependent on (2 factors)? What is the threshold for the role?
- Natterjack toads - females –> loudest calls = largest males set up territories w/ most females
- Satellite
- Your loudness and other toads around you
- You call if you are 50% as loud as neighbor (you 50, neighbor 80 = call)
What is a second example of conditional strategies with alternative mating tactics? What is the role for each? What does horn development depend on? What does the fitness v competitive ability graph look like for this scenario? What is the threshold for having a horn, and why is it so?
- Dung beetles - two morphs (long horn and small horns), larger body size = larger horns
Small body size = sneaking into the dung
Large body size = guard the opening of the tunnel
- Depends on the amount of dung available to growing larvae (hormonal switch dependent upon body size)
- In this case, competitive ability (low to high on axis) is essentially body size (can you compete with others).
Two tactics are on the graph (horn and no horn). There is not a huge change in fitness for the no horn group as their competitive ability increases (because they are still below the threshold).
However, fitness is greatly influence by body size if the beetle has a horn (will have a lower fitness than the no horn at smaller body sizes, then greatly increase by the time body size is large)
- success greatly increased for males above 5mm, suggesting a 5mm threshold for whether to have a horn.
What was the strategy set for the dung beetle example?
Horns v body size (not horn or no horn) (single allele)
What was the result of the experiment from Emlen to test whether evolution of the threshold was possible? What did this prove? Describe the experiment as well.
Description: Had two lines of artificial selection. One was big horn that only let big horns reproduce, and the other was small horns that only let small horns reproduce.
Results: The thresholds shifted based on the line.
Proved: Selection should result in evolutionary change of the strategy details.
What are two examples of maintenance of strictly genetic polymorphisms? How are they maintained?
- Ruffs and side-blotched lizards
- Frequency-dependent selection
Explain the ruff example of maintenance of genetic polymorphisms. What are the three morphs? How are they determined? Why do two out of the three types have a higher fitness when they are rare?
- Independent territory owners - dark plummage, 80-90% of lek
Satellite males - white plummage, assist with female attraction to steal copulations (5-20%)
Faeder males - female mimics to steal copulations (<1%)
- Determined with a supergene. Satellite is one, and faeder is another.
- They both have a higher fitness when rare because 2 copies of supergene = dead, so them being rare means they have less of a chance of accidentally mating with each other.
Explain the side-blotched lizard example of maintenance of genetic polymorphisms. What are the three morphs? How are they determined? How are they maintained? Is there is a stable polymorphism, why or why not?
- Orange-throated (aggressive, defend large territories with many females)
Blue-throated (defend small territories + guard single female)
Yellow-throated (receptive female mimics + no territories, sneak)
- Determined by: 3 alleles on a single locus:
o - dominant to other two
y - dominant to b
b - recessive all around
- The polymorphism itself is maintained (exists still) because o beats b, y beats o, and b beats y.
- There is no stable polymorphism because there’s a cycle between the three strategies (ever-changing who is doing better). When rare = winning, when common = losing (and if others are winning then their population will increase and then they’ll be losing again)
