L12

Question 1

Examples of species that co-operatively breed:

Answer 1

-Meerkats

• Social insects

Question 2

What is co-operative breeding characterized by?

Answer 2

• The presence of helpers
• Eg cleaning, mutualistic feeding
• Individuals who help hamper their own reproductive success

Question 3

Diversity of cooperative systems

Answer 3

• Cooperative breeding has different interpretations
  • Most widespread in birds 4-9% of bird species
  • 3% of mammal species
  • Described in >10 fish species
  • Social insects that aren’t yet eusocial

Question 4

In what species is cooperative breeding most widespread?

Answer 4

Birds

Question 5

Helpers at the nest e.g. Florida Scrub Jay

Answer 5

• Florida scrub Jay
  • Pair + 1.8 helpers
  • Helpers feed and protect young from predators
  • Helpers usually related to breeding pair

Question 6

Helpers at the nest eg Silver backed Jackal

Answer 6

• Pair + 1-3 helpers
• Helpers regurgitate food to pups and lactating female

Question 7

Helpers at the nest eg Naked mole rat

Answer 7

• Naked mole rat
  • Larger societies up to 80 individuals
  • Queen breeds
  • Normal moles have different morphology to queen
  • Reproductive division of labour (some fight, some forage, reproductive female breeds in chamber)
  • Dispersal morphs who try and founder new colonies
  • Debated whether it is a caste system or part of species aging

Question 8

Plural breeders

Answer 8

Several males and females share a nest and raise a communal brood

Question 9

Banded mongoose

Answer 9

-Plural breeders

- 4-40 individuals in a group

- Several reproductive females and males

Question 10

Acorn woodpecker

Answer 10

• Plural breeding
  • 2-14 individuals in a group
  • Reproductive individuals are often brothers and sisters
  • These breed with individuals that have moved into the colony
  • Helpers are non-breeding

Question 11

Ecological constraints hypothesis

Answer 11

Independent breeding is constrained - thus leading to grown offspring delay dispersal and stay at home
1. Habitat saturation/ ecological constraints

Grown offspring delay dispersal and stay at home leads to grown offspring helping to rear later broods

2. Fitness benefits of helping exceed those of not helping

Question 12

Main assumption of the evolutionary constraints hypothesis

Answer 12

there is a better fitness return from breeding than helping (but breeding is constrained)

Question 13

Species Example eg Long-tailed tit

Answer 13

Genetic equivalents = fitness

Breeding productivity = 0.5 GE
Helping = 0.14 GE

Hypothesis: constraints cause offspring to delay dispersal instead of breeding independently

Correlational evidence

- Bad years =  more helping

- Good years = less helping

Question 14

Acorn woodpecker

Answer 14

• In nearly all bad years (low acorn crop) there is high delayed dispersal
  • In good years (high acorn crop) there is less delayed dispersal

> 2Y acorn woodpeckers

- Less delayed dispersal

Question 15

Superb fairy wren

Answer 15

• 60% of pairs have male helpers
  • Arise due to male sex ratio
  • Sex ratio at birth is 1:1 but many females die so it is 1.8M: 1F

Question 16

Are fairy wren helpers constrained from breeding experiment 1?

Answer 16

Male removed from pair

Leaving 33 vacancies for 33 helpers

31/33 vacancies filled by helpers (within 5 hours)

Question 17

Are fairy wren helpers constrained from breeding experiment 2?

Answer 17

• Removed male and female
  
  • Empty territories
  • Initially helpers didn’t take over territory as there was no reason (no one to mate with)
  • Female released (after 3 days) then 7/7 vacancies filled
  • No interest in helping, strictly reproducing

Question 18

Are fairy wren helpers constrained from breeding conclusions

Answer 18

• Helpers are capable of reproduction
  
  • Habitat is limiting (ECH)
    
    • mates are limiting

Question 19

Experimental work has revealed different constraints such as…?

Answer 19

• Food
• Nest cavities
• Territory and mate
• High quality territory (food)

Question 20

How do helpers benefit from helping?

Answer 20

Direct fitness: fitness gained from personal reproduction

and

Indirect fitness: fitness gained from increasing production of non-descendant kin ( via kin selection)

Question 21

The three direct fitness benefits:

Answer 21

• Increased survival
• Increased probability of future breeding
• Direct reproduction

Question 22

Group augmentation hypothesis

Answer 22

Benefits may select for helpers to then keep adding to benefits

Question 23

Increased survival

Answer 23

• Group augmentation hypothesis

Producing extra offspring benefits helpers by increasing group size

Kidnapping in banded mongoose and white-winged chough

Gaining benefits associated with larger group living

- Some cons of group living but benefits must outweigh for it to occur

Question 24

Experimental evidence for increased survival

Answer 24

• Cichlid groups more likely to accept immigrants when predation risk is high

Question 25

Increased probability of future breeding

Answer 25

Territory inheritance 48% of helpers eventually acquire all or part of parental territory so they can become breeders Mate acquisition - Pied kingfishers Primary helpers - Relatives Secondary helpers - Not relatives - Don’t benefit indirectly but buy their way into a territory and inherit female when the male dies Kick out breeding male sometimes

Question 26

Increased experience (skills hypothesis)

Answer 26

- Comparison of success of various breeders eg 1st time, previous breeders - 1st time breeders who never helped had no/ low reproductive success - 1st time breeders who helped had more reproductive success as did previous breeders

Question 27

Direct reproduction

Answer 27

- 44% lay eggs in helped nest - 15% of all young produced by 'helpers' - Helpers are usually female - Helpers taking advantage of producing their own offspring - Not strictly helpers

Question 28

Indirect fitness benefits

Answer 28

- Increased reproductive success of relatives - Increased survival of related breeders

Question 29

Increased reproductive success of relatives

Answer 29

- Long-tailed tit - Reproductive success increases with no of helpers - Raised by offspring alone reduces survival chance - If helpers Is related there is a large indirect payoff White fronted bee-eater - Reproductive success increases with no of helpers - However these correlation studies may be a result of more individuals in group size, more experienced parents etc

Question 30

Does removal of helpers impact reproductive success?

Answer 30

Removal experiments - Socially disruptive - No sig effect on all species, but some species there is an effect

Question 31

Increased survival of related breeders

Answer 31

= load-lightening - Investing more in reproduction means less in self- maintenance - Helpers can assist with costs Hatchwell 1999 - 20/26 species of cooperative breeder - One or both parents reduce their effort when assisted by helpers - improved parental survival hard to demonstrate Helpers are typically related to breeders