1. Eusociality Conflicts over reproduction Definition and occurrence
Explanations for worker sterility
Routes to sociality

2. Definition Overlapping generations
Reproductive division of labor including nonreproductive (or sterile) workers
Caste polymorphism (in some cases)
Parental care in a permanent nest

3. Hymenoptera: ants, bees and waspsC E

4. Ants show caste polymorphism

5. Isoptera - all termites

6. Social aphids

7. Gall-forming thrips

8. Carribean snapping shrimp

9. Naked mole rats

10. Social spiders
Communal, but no sterile caste

11. Why worker sterility?
Kin selection
Parental manipulation

12. Haplo-diploidy and relatedness

13. Why worker sterility? Kin selection
Because of haplodiploidy, workers are more closely related to sisters (r = 3/4) than to offspring (r = 1/2), assuming females mate once
But, they are more closely related to male offspring (r = 1/2) and nephews (r = 3/8) than to brothers (r = 1/4). Therefore, workers should lay unfertilized eggs if mothers mate singly (bumblebees, stingless bees)
If mothers are polyandrous, then female workers may be more closely related to brothers than half-nephews (r = 1/8). Expect workers to kill unfertilized eggs laid by other workers in polyandrous species, e.g. honeybees.

14. Worker policing in honeybees
“Queenright”
“Queenless”

15. Why worker sterility? Parental manipulation
If parents can prevent their young from reproducing, then it may be better to help
A mother that traded eggs with her daughters would trade grandkids (r = 1/4) for offspring (r = 1/2) and gain a 2-fold advantage. Daughter trades offspring for siblings and loses nothing (r =1/2 for both).

16. Sex ratio investment
Offspring control: expect 3:1 investment sex ratios because females are related to sisters by 3/4 and to brothers by 1/4
Parental control: expect 1:1 sex ratios
Data fit 3:1, rejects parental manipulation
Only slave-makers are 1:1

17. Factors promoting eusociality
Genetics
High relatedness of workers to reproductives
Ecology
High cost of dispersal
Need for assistance in nest construction
Reproductive success is proportionately higher for family than individual
Need to defend a multi-generation nest

18. Routes to sociality
Predict r < 0.5
Predict r > 0.5

19. Paper wasps, often single foundress

20. Swarm founding wasps

21. Inbreeding-outbreeding cycles in termites
Termites are diploid.
Both sexes help.
In some species, multiple
reproductives occur.
If these are produced by
inbreeding over multiple
generations, then termites
within a colony could
be very closely related

22. Inbreeding in mole rats?