Evolutionary and Behavioural Ecology

Evolution

Evolution is change: changes in traits (or allele frequency) over time. Is driven by natural selection.

Natural selection

The mechanism that drives adaptive evolution. Evolution by natural selection results in adaptations to the ancestors' environment. Not random.

Famous example:

• Peppered moth (Biston betularia) in England during the industrial revolution.

Mutations

Mechanism that drives evolution. Can be a positive or negative change in the genetic composition of an individual. Occurs randomly.

Variation

Differences in traits among individuals. Variation arises through random mutations or from natural selection.

Heritability

A measure of how well differences in people's genes account for differences in their traits. Offspring inherit many traits from their parents.

Directional selection

A single phenotype is favoured, causing the allele frequency to shift in one direction.

Stabilizing selection

Genetic diversity decrease as the population stabilizes on a particular trait value.

Disruptive selection

Extreme values for a trait are favoured over intermediate values.

Counter gradient variation

The environment conceals genetic variation.

Ex. tadpoles in northern vs. southern Scandinavia.

Ecomorphs

Genotypes that correspond differently to certain climates.

Allopatric speciation

Speciation by division of a natural barrier. Occurs from geographical isolation.

Sympatric speciation

Speciation happening in the same area. Occurs in the same geographical area.

Character displacement

Natural selection favors a divergence in the characters when two similar species inhabit the same environment.

Genetic drift

The change in the frequency of an existing gene variant (allele).

Phenotypic plasticity

A single genotype alters its phenotype in response to environmental conditions.

Fitness

Contribution of an individual to future generations. Individuals have higher fitness if they leave more descendants.

Fitness benefits are maximized when…

… the difference between costs and benefits are the largest.

Coevolution

Occurs when two or more species mutually affect each other's evolution through the process of natural selection.

Gametic selection

Important form of selection but rarely in the context of ecological interactions. Occurs at the gametic level (haploid stage).

Kin selection

As relatives share genes, natural selection favors alleles that benefit close relatives. Important in evolution of social organization and co-operation.

Inclusive fitness

Individual selection and kin selection together determine an individual’s inclusive fitness, which is the sum of direct fitness and indirect fitness.

Altrusitic

A trait (often behaviour) which is beneficial to the recipient but costly to the donor.

Group selection

Occurs at the level of (isolated) groups of organisms. For example altruistic behavior for the good of the species or the group.

Monophage

Consumer of only one type of food. Specialists.

Oligophage

Consumer of a limited variety of food. Specialists.

Polyphage

Consumers of a high variety of food. Generalists.

h

“Handling time” - ex. time it takes for a predator to handle its prey.

s

“Search time” - ex. time it takes for a predator to search for its prey.

h < s

Predators with long search time should be generalists because it takes relatively short time to handle a prey when it is found.

h > s

Predators with long handling time relative to search time should be specialists since searching for prey is not an issue.

Why do animals live in groups?

Predation:

• More eyes – higher chance of finding food, easier to spot predators. Individuals on the edges/corners are usually the ones that are on the lookout for predators – often younger individuals that require less food.

• Numerical dilution of risk > predator attraction – if you’re in a flock, the chances that a predator picks you specifically significantly reduce

• Edge effect

• Confusion effect

• Defence – prevents predators from attacking from behind for an example

Food:

• More eyes find more food

• Copying successful individuals

• Cooperation when hunting

• Copying successful individuals

• Cooperation when hunting