Notes on all lectures "Evolutionary Ecology" (RUG; 1st year)
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Course
Evolutionaire Ecologie (WBBY03805)
Institution
Rijksuniversiteit Groningen (RuG)
This document contains notes of all lectures given for the course “evolutionary ecology” on the study biology at the University of Groningen (first year)
Evolutionary ecology
Lecture 1: Introduction (28/02)
Ecological perspective
Beak shapes are adapted to eat different things; different morphology (in beak and jaw) in fish that
suck and bite; unrelated species in different lakes that are very similar (convergent evolution)
Evolutionary perspective
Light conditions cause that fish cannot recognize other species; high transmission in blue
wavelength; the wider the spectrum (see more colors, less turbid water), the more species
→ Understanding of interactions with other organisms and environment (ecology) critical for
understanding evolution; species and interactions are the outcome of evolution → ecology and
evolution go hand in hand
Lecture 2: Optimality (28/02)
Tinbergen’s four questions:
- Ultimate questions (why?): natural selection
1. Function (adaptation)
2. Evolutionary history (phylogeny)
- Proximate questions (how?):
1. Causation (mechanisms)
2. Individual development (ontogeny)
Why did butterflies migrate and how did migration evolve → ultimate
How do butterflies navigate and how do they know when to migrate → proximate
Ultimate question is what sets evolutionary biology apart from all other sciences; in other sciences,
proximate questions most important
Ultimate (why) questions: natural selection
- Intraspecific competition (struggle for existence)
- Differences in fitness (capacity to survive and reproduce; contribution of genes to gene pool;
Darwinian fitness);
- Fitness differences must be heritable
Expectation: population composition changes toward
improved fitness
X and Y are traits → different combinations of these traits
yield different fitness → optimal combination is highest peak
(highest fitness)
Optimality paradigm: explain adaptations in terms of fitness
maximization; proxy used (measuring fitness is difficult);
offspring produced
Example: optimal flight speed in birds
Power (BMR) per unit time: basal metabolic rate: y axis
Velocity: x axis
→ the higher the velocity, the higher the power (except for very low velocity)
, - Hypothesis 1: birds minimize
power needed to fly → flight
speed is at lowest point of
power
→ true flight speed is higher
→ hypothesis rejected
- Hypothesis 2: birds minimize
energy per distance
Minimize the slope (find
tangent)
Optimality approach:
1. Specify available options
(strategies); what is option
set
- Information: What is
known?
- Constraints: What is possible? → include all possible velocities of an animal
2. Derive fitness consequences
- Currency: proxy for fitness (in example: fitness currency is energy tradeoff)
- Trade-offs (some animals invest more in reproduction; survival vs reproduction)
- Cost-benefit analysis (first be aware of currency and trade-offs)
3. Determine optimal solution
4. Compare observed behavior with optimal behavior
5. Improve optimality model
Research process: verbal/formal model is based on a lot of assumptions → data can match or not
match expectations, causing hypothesis to be or not to be rejected
Copulation duration in dungflies
- Dungflies copulate for 40 minutes; 5 minutes would be sufficient
- What are the options → all possible copulation times
- What are benefits/costs or
longer copulations?
1. Benefits: higher
fertilization success
(diminishing returns)
2. Costs: time lost for
finding and fertilizing
other females
(opportunity costs);
average search time is 160
min
- How do we define fitness?
, Hypothesis: fitness = eggs fertilized per time invested (time copulating + time searching)
→ make graph in excel → optimal copulation time indeed t = 40 min
Good fit between predictions and observations
Time required to find new opportunity (time in patch): time on negative axis
Yield per time corresponds to the slope of green line → find maximal slope
Marginal value theorem: whenever “yield per time” is maximized, the optimal time can be found
graphically
Foraging behavior of honeybees
Flight becomes more expensive when bees carry pollen
- How many flowers to visit before returning to hive? (how much energy is contributed to the
hive net); cost becomes more important the longer the flight time between flowers
- Currency: maximizing delivery rate to the hive?
Result: bees go past way less flowers → optimality model failed
Options for failing model
- Behavior not yet optimal; evolution has not caught up yet
- Evolutionary problem not adequately represented (flight time also affects chances to be
caught by predators, not only energy expenditure)
- Currency chosen no adequate representation of fitness
- Constraints are not adequately represented; option set is different from what we assumed
Plausible proxies for fitness
Maximization of energetic efficiency does
correspond to foraging behavior in bees → do not maximize delivery
rate but energy efficiency; currency chosen was not an adequate
representation of fitness
Physiological and ecological constraints
Duration of low-water period is of effect on the food consumption;
- There is a maximum food intake
- There is a maximum on how much food can be digested per
unit time; increases when amount of time they have to eat
increases
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