12: eusociality Flashcards
what are the 3 main orders with eusocial systems ?
hymenoptera
isoptera
homoptera
within hymenoptera how many species are eusocial? (3)
bees: 1,000
wasps: 800
ant: 9,500/all
in isoptera how many species are eusocial?
termites: 2,000
in homoptera what species is eusocial?
aphids
what are the 3 main features of eusocial species?
- cooperative brood care (non parents help raise brood)
- sterile castes
- overlapping generations (workers raise subsequent broods)
how many total species of social insects? - how many birds and mammals?
14,000
birds: 10,000
mammals: 4,000
how many ants in the driver ant colony?
22 million
in the brazilian rainforest what % of insect and animal biomass is eusociall?
insect: 70-80%
animal: 33%
what is an example of sophisticated communication in eusocial species?
waggle dance
what is the ant myrmica rubra life cycle? (6)
- queen founds nest
- sterile workers produced
- 9 years for colony to be large enough
- after 9 years winged females and males produced
- nuptial flight and mating
- males die and females find a nest
list the 2 hypotheses for why eusociality evolved
- staying at home/subsocial
- sharing a nest/ parasocial
what is the ecology for how eusociality evolved by the staying at home hypothesis? (4)
- ancestors are solitary parasitoids
- advantage to nest guarding by females against parasites
- if enough predation pressure young stay and help mother defend and build nest
- will stay at home and never breed
what is the genetic predisposition for how eusociality evolved by the staying at home hypothesis? (3)
- for daughters at home raising full siblings (r=0.5) is the same as raising offspring (r= 0.5)
- for queen producing offspring (0.5) is better that grand offspring (0.25)
- queen should prefer daughters to stay as workers
what is the ecology for how eusociality evolved by the sharing a nest hypothesis? (4)
- cooperating sisters build nests close together
- cooperative defence but separate reproduction
- one female dominates reproduction
- young females become workers
what is the genetic predisposition for how eusociality evolved by the staying at home hypothesis? (3)
- for cooperative sisters there is benefit to raising dominants offspring
- this may outweigh benefit of breeding alone if it is risky
- relatedness ensures non reproductive female benefits from queens reproduction
what is an example of a species that fits with the stay at home hypothesis?
subsocial halictine bees
what is an example of 2 species that fit with the sharing a nest hypothesis?
polistes
stenogastrine waps
what did W.D Hamilton say about haplodiploidy?
it predisposes hymenoptera to evolve sterile castes
what are features of M and F in haplodiploidy?
M: from unfertilised eggs, haploid and form gametes without meiosis so all sperm identical
F: from fertilised eggs, diploid and form gametes with meiosis
where do sons and daughters receive their genes in terms of mother and father?
- sons: only from mother
- daughters: identical genes from father and other half from diploid mother
in the sister-sister pedigree what is the relatedness
a) via mother
b) via father
c) total
a) 0.5 X 0.5 =0.25
b) 0.5 X 1 = 0.5
c) 0.25 + 0.5= 0.75
in the sister-brother pedigree what is the relatedness
a) via mother
b) via father
c) total
a) 0.5 X 0.5 =0.25
b) 0.5 X 0 = 0
c) 0.25
in the brother-sister pedigree what is the relatedness
a) via mother
b) via father
c) total
a) 1 X 0.5 =0.5
b) 0.5 X 0 = 0
c) 0.5
what is the genetic relatedness between female and
a) mother
b) father
c) sister
d) brother
e) son
f) daughter
a) 0.5
b) 0.5
c) 0.75
d) 0.25
e) 0.5
f) 0.5
what is the genetic relatedness between male and
a) mother
b) father
c) sister
d) brother
e) son
f) daughter
a) 1
b) 0
c) 0.5
d) 0.5
e) 0
f) 1
what is it better the female worker produces and what does it explain?
sisters rather than daughters
- explains why females rear sisters
in hymenoptera what are workers always?
female
what are diploid termites like?
M and F equally related to siblings and both sexes become sterile workers
what are clonal aphids like?
- all are genetically identical r=1
- sterility is not an evolutionary puzzle as is no conflict over reproduction
what is the preferred sex ratio for the queen and why?
son r=0.5
daughter r=0.5
1F:1M
what is the preferred sex ratio for the worker and why?
brother r=0.25
sister r=0.75
3F:1M
what did Trivers and Hare 1976 study and find? (3)
- sex ratio in 21 ant species
- suggested workers win
- but the preferred ratio is influence by local mate competition and queen mating frequency affecting relatedness
what is local mate competition? (2)
- if sons/brothers compete to mate such as in fig waps then it should pay to produce fewer of them
- benefit to female biased sex ratio
what is queen mating frequency affecting relatedness? (3)
- if females mate with multiple males then workers are less closely related
- if 2 possible fathers: r= 1 X 0.5 X 0.5 = 0.25 (+ 0.25 from mother = 0.5 relatedness)
- if infinite males then r= 0
what are ecological constraints important in?
evolutionary origins
what can eusocial species also be characterised by?
conflict within and between castes
