Lecture 13: Eusociality Flashcards
what is eusociality?
it describes social systems where there is cooperative brood care, generational overlap, and, critically, sterile castes
diversity of eusocial systems = how has it evolved?
involved independently in hymemoptera (bees, wasps ants), isoptera, homoptera
three features of a eusocial system:
- cooperative brood care
- sterile castes
- overlapping generations
why are eusocial systems ecologically important?
spread across world in many systems, evolved remarkable specialisation to suit social way of life
how man species of insect show eusocial systems?
14,000 (10,000 birds, 4000 mammals)
eusociality driver ant colony: how many ants
22 million ants
brazillian rainforest % of insects
70-80%, 33% animal biomass
example of sophisticated communication
waggle dance
Myrmica rub life cycle
- nuptial flight and they mate just ONCE
- queen then founds nest
- production of sterile female workers
- around 9 years later
- produce winged females and males
how many hypothesis’ to suggest how eusociality evolved from solitary ancestral forms?
2
- staying at home
- sharing a nest
hypothesis of eusociality evolution: Staying at home
- solitary parasitoid
- nest guarding by female
- young then stay & help defend/build (help outweighs benefits of them having own young)
- young permanently at home and never breed
- –Relativeness makes it worthwhile; daughters raising full siblings = as good as raising offspring
- queen should prefer daughters to stay as workers
hypothesis of eusociality; sharing a nest
- sisters build nest close together
- cooperative defence, separate reproduction
- one female dominates reproduction
- young females become workers
- helping sisters may outweigh the benefits of breeding alone as may be high risk activity
who proposed haplodiploid & what is it
W.D Hamilton
- M from unfertilised eggs = haploid
- F from fertilised eggs = diploid
-males form gametes without meiosis (all gametes identical)
F form gametes with meiosis
haploiddipoidy: daughter and sons genetic make up
- daighters receive identical genes from father & the other half from diploid mother
- sons receive genes only from mother
haplodiploid = in eusocial insects sisters are related by
- 75
0. 25 from mother and 0.5 from dad
haplodiploid = in eusocial insects sis to bro
0.25
haplodiploid = in eusocial mother to son and daughter
0.5
so female worker point of view better to produce daughter / sisters?
DAUGHTERs as = 0.75 relatedness
-explains why females (not males) rear sisters
compare haplodiploid to diploid termites
m & f equally reloads to siblings ad both sexes become sterile workers
consequences with haplodiploid who studied this
-Trivers & Hare 1976 sex ratio in 21 ant spp,
generates conflict between queen and daughters
- queen want to produce 1 daughter for every son
-but worker would favour daughters (0.75 relatedness) (3:1 f:m)
-WORKERS WIN
criticism of consequences with haplodiploid who studied this studies Trivers & Hare 1976
- local mate competition -> queen may want females too
- queen mating frequency affects relatedness
Local mate competition: Fig wasps
- fig wasps lay eggs into figs through outer surface, larvae develop in fig and eventually emerge
- male have large penis’ allowing them to mate with females before they’ve emerged
- female putting eggs in figs, would make sense for them to bias females
Queen mating frequency affects relatedness
reduction in relatedness the more males she mates with
eusociality has evolved …
multiple times in various taxa
ecological constraint likely tone important in ____
Evolutionary origins
incentive of genetic predisposition to help, especially in
haplodiploid Hymenoptera
Eusocial species are also characterised by conflict within and between ___
castes
