Unit 2 Lecture 6 - Behavioural Ecology PDF

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BIOL1011 - Ecology Unit! Professor Derek Tittensor

Thursday, February 27, 2020

Lecture 6 - Behavioural Ecology Readings: Pages 1213, 1214-1218, 1207-1209! Behaviour and Natural Selection

- Those with more appropriate behaviour pass on more genes:! - More likely to survive! - More likely to produce offspring! - We explain behaviour in terms of effect on individual fitness! - Benefit: if fitness increases! - Cost: if fitness decreases! Social Behaviour

- Cooperative: defense, hunting! - Selfish: territoriality! - Spiteful: surplus killing! Behaviour

- Should have a fitness advantage! Inclusive Fitness!

- The total effect on number of genes passed on! 1) Produce offspring! 2) Aid relatives to produce more offspring! Kin Selection

- Selection for an act that enhances relative’s reproductive success!

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BIOL1011 - Ecology Unit! Professor Derek Tittensor Hamilton’s Rule

- Natural selection favours an act if C < r B - C: Cost to altruist (lost reproduction)! - B: Benefit to recipient (increased reproduction)! - r: Relatedness (shared genes)! Pikas

- Cost of alarm small! - Related to neighbours! Reciprocal Altruism Between Non-Relatives

- Tit for tat! - Stable social groups! - Culture! Social Organization

- Being social - when is it worth it to live in a group?! - Benefits:! - Cooperative feeding! - Defense of group! - Costs:! - Disease/parasites! - Restricted reproduction! - Group living evolves when benefits > costs!

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Thursday, February 27, 2020

BIOL1011 - Ecology Unit! Professor Derek Tittensor

Thursday, February 27, 2020

Restricted Reproduction and Social Organization 1) Cooperative Breeding! Wolves!

- They live in packs! - Restricted reproduction! - Social hierarchy - only some breed! - Alpha male and female(s)! - Benefits of staying to help:! - Kin selection: sibling survival means pups survive better in packs with helpers! - Individual fitness: get stronger and gain experience, more likely to survive when they leave, higher lifetime reproduction! Florida Scrub Jay!

- Live on territories in family groups! - Benefits of staying to help:! - Breeding pair: build nest and incubate eggs! - Mature young stay on territory: feed younger siblings, defend territory, warm of predators!

- Why do sons stay? Scrub oak habitat is very limited and there are few chances of finding an open territory!

- Oldest male gets family territory if father dies and territory partitioned! - Females never inherit family territory! - Kin selection: sibling survival! - Individual reproductive fitness: inherit territory in the future - sons only!

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BIOL1011 - Ecology Unit! Professor Derek Tittensor

Thursday, February 27, 2020

2) Eusocial Societies! Army Ants!

- Reproduction: one queen and several males! - Workers: all sterile females who are in charge of defense, foraging, and care for young!

- Benefits of staying to help:! - Kin selection: sibling survival! - Individual reproductive fitness: none! Naked Mole Rat!

- Arid habitats, Horn of Africa! - Colonies live in underground burrows! - Benefits of staying to help:! - Male and Female workers dig tunnels, gather food and nest material for young! - Soldiers defend and burrow! - Reproduction: 1 female, 1-3 males! - Coercion: Queen suppresses reproduction in the colony: behaviour and chemicals! Why don’t naked mole rats leave the colony and reproduce on their own?

- Harsh environment and food is very scarce! - Can’t survive in small groups! - If they leave, fitness = 0! - If they stay, inclusive fitness > 0! - Benefits of staying to help! - Kin selection: sibling survival! - Individual reproductive fitness: none! 4

BIOL1011 - Ecology Unit! Professor Derek Tittensor

Thursday, February 27, 2020

Environment influences costs and benefits of group living

- Group living evolves where: total fitness for staying in the group > independent reproduction!

- It pays to give up or delay independent reproduction if:! - Chance of independent reproduction is low! - Survival is difficult (harsh environment - mole rat)! - Opportunities for reproduction are few (limited habitat scrub jay)! - A delay increases future reproduction potential (red wolf)! Types of Mating Systems Monogamous!

- Single pair bond! Polygamous!

- One individual mates with several of the other sex! Promiscuous!

- No strong mating bonds! Polyandry in spotted sandpipers

- Females first to arrive at breeding grounds! - Compete for males as they arrive (females larger)! - Females desert nest after eggs are laid! - Produce eggs with another male! - Environmental conditions:! - Enough food for one parent to rear chicks! - Females produce few eggs at a time! - Season long enough for more than one clutch of eggs!

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BIOL1011 - Ecology Unit! Professor Derek Tittensor Why do animals behave the way that they do?

- Behaviour shaped by selection: benefits > cost! - Inclusive fitness (kin selection)! - Vary with environment!

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Thursday, February 27, 2020...