Midterm 1 - Sociality and Inbreeding Depression, Foraging Flashcards
What are social spiders?
Spiders that live in colonies. These spiders cooperate in brood care, maintenance of the nest, feeding and cooperate in capturing prey.
Are social spiders common?
No, they are exceedingly rare. Most spiders are solitary
We know of about _____ species of social spiders, _____ of them having evolved sociality independently. All of these spiders are distributed around the ____
20 social spider species
18 evolved sociality independently
All of them are distributed around the tropics
Is there mixing between individuals from different colonies even if they are the same type of social spider species?
No mixing between colonies. Mating happens only within colonies.
Within spider genera, there’s a range of social behaviour. It goes from being solitary (no social behaviour), to subsocial, to social.
What are subsocial spider species? Are they inbred or outbred?
These are species in which the young are taken care of by the mother, until they are adults and then when they reach adulthood, they disperse and find unrelated mates.
Because they disperse to mate with non-relatives, they are considered outbred.
Define “Inbreeding Depression.”
A reduction in fitness in a population as a result of inbreeding.
Why is inbreeding depression bad?
All spiders, including the outbred ones, carry recessive deleterious alleles. Those that are outbred don’t have it expressed because they have high genetic variation (from mating with non-relatives).
Inbred spiders are likely to carry the same type of deleterious recessive allele. Such that the bad phenotype is more likely to be expressed in their offspring if they mate.
Studies show that social spider species have originated from what kind of spider ancestors?
subsocial spider ancestors
What is the formula for inbreeding depression?
IB = 1 - (Winbred/Woutbred)
True or false. To find fitness, you usually have to look at traits that are correlated with fitness.
True
What is one reason we discussed in class that could explain why the transition from outbred subsocial species to inbred social species has happened?
An experiment by Leticia concluded that:
Inbreeding depression is evident in solitary, but not social phases of the lifecycle of a subsocial spider species (that has been manipulatively inbred)
Maternal care probably buffers the negative fitness effects of inbreeding on the social phases (i.e. the baby phases) of the lifecycle.
One of the things an animal must do in order to pass their genes is to find food. Behavioural ecologists use the word ___________ to describe finding food
foraging.
What characteristics of food items are relevant for a forager when choosing what food items to include in their diet? (8 things)
- The abundance
- The distribution
- Seasonality
- The size of the food item
- How accessible it is/how difficult to acquire it is
- Escape ability
- Nutritional value
- Palatability/Toxicity of food item
What is the Optimal Foraging Theory?
A theory that explains that animals will choose a foraging strategy that maximizes the benefits and minimizes the cost, to create an optimum foraging strategy.
What is an optimality model? Did we look at an example of this in class?
A graphic tool used to portray costs and benefits of animal behaviours. In class we had an example of optimality models using “food choice” as the behaviour, with oystercatchers and mussels.
Oystercatchers have been seen to prefer intermediate-sized mussels in the wild. What does this say about the NET energy gain curve? Please don’t mistake this curve as the benefit curve.
The net energy gain curve is the benefit curve minus the cost curve.
If oystercatchers prefer intermediate mussels, that means the NET ENERGY CURVE is maximized there i.e. the peak of the curve coincides to intermediate sizes on the x-axis.
What is the benefit we’re talking about when considering the benefit curve for oystercatcher mussel size choice?Does the benefit curve increase linearly for mussel size in oystercatchers?
The benefit is the amount of energy. Mussels that are bigger are greater sources of energy than smaller ones.
No, it will increase but then plateau. This is because there is only so much energy the oystercatchers can gain from one mussel, the animal gets satiated at the same point regardless of how big the mussel is.
How does the cost curve change in the oystercatcher mussel size case? Does this curve plateau?
The cost goes up exponentially with size. This is because bigger mussels have a longer handling time. The curve does not plateau
The distance between the cost curve and the benefit curve would be __________(lowest/greatest) at intermediate mussel size
greatest
True or false. In an optimality model, the distance between the cost curve and the benefit curve should always be greatest at the most optimum food item size.
true
Are the oystercatchers making a conscious choice when they go for the intermediate mussels, i.e. are they weighing the benefits and costs in their heads like an economic transaction?
No.
Natural selection has simple evolved to favour individuals that go for intermediate mussels, since those individuals receive the maximum benefit, and are thus more fit.
One mathematical statistic that is used in the Optimal Foraging Theory is __________
profitability
What is profitability? What is the equation for it and what do the variables stand for?
A mathematical statistic that measures the NET gain in ENERGY one obtains from eating a certain food item.
The equation is..
profitability = Ei / hi
where Ei is the energy gained from eating the food item “i” and hi is the handling time spent on the food item “i”
Can eating small items ever be preferred over large ones i.e. profitability is higher for smaller food items than larger ones?
In the profitability equation, profitability = Ei / hi, we can increase profitability if the handling time is really short/fast. So if small food items have very small handling times, it might be more profitable to eat smaller food items.
