Ben Hatchwell 2 Flashcards
What is special about many social insects is that…
many individuals forgo reproduction entirely (they are sterile and can never reproduce)
Eusociality occurs most commonly in 3 groups of insects:
Hymenoptera (ants, wasps, bees), Isoptera (termites) - infraorder of Blattoidea, Homoptera (aphids) - suborder of Hemiptera
Every species of … is eusocial
ant
In termites, soldiers … the …, and the offspring are protected by the ….
protect, queen, workers
Aphid eusociality is typically associated with … formation
gall
- queen produces clones of herself
What are the three features that define eusociality?
- Cooperative brood care (individuals who are not the parents of offspring help to raise broods in the nest)
- Sterile castes
- Overlapping generations (workers raise subsequent groups of offspring produced by the queen)
Look at pic on phone for termite castes
they’re pretty groovy looking
Nasute soldiers in termites can…
spray intruders with toxic and glue-like substances
Eusocial insects are ecologically very important. There are estimated to be … species of social insect. To put that into context there are 4000 mammal species total and 10,000 bird species.
14,000
A single driver ant colony can be made up of … … individuals
22 million
In the Amazon rainforest, social insects are estimated to make up … … of animal biomass
a third
Eusocial insects can have sophisticated forms of communication, for example…
the waggle dance (bees use to communicate the location of high quality food sources)
There are many specialisations in eusocial insects, for example Nasute termites and their … and some honeypot ant workers who are specialised as … …, filling their abdomens with it.
nozzles, honey stores
Typical lifecycle of a hymenopteran social insect (using Myrmica rubra, a species of ant, as an example):
- … … finds a nest (underground) - won’t mate again for entire life - only mated once before finds nest
- Queen produce … … workers
- Workers grow in number, helping to raise more and more workers - takes Myrmica rubra about … years to form a large enough colony to start sending out … ants
- After this period, the queen switches from producing sterile workers, to producing … females and males
- These leave the colony, undergo a … flight and mate. The males subsequently proceed to … and the females lose their … and find a nest
fertilised queen, sterile female, 9, reproductive, winged, nuptial, die, wings
How did eusociality evolve? Thought to be two pathways: the “… … …” hypothesis and the “… … …” hypothesis
staying at home (subsocial), sharing a nest (parasocial)
What is the staying at home hypothesis?
Solitary … –> nest … by female –> young stay and help …/… –> young … at home and never ….
From a genetic predisposition standpoint:
For daughters, raising full siblings (coefficient of relatedness, r = …) is as good as raising own offspring (r = …).
For the queen, producing offspring (r = …) is better than producing …-… (r = 0.25) - should prefer daughters to stay as workers
parasitoid, guarding (advantageous to stop predator eating or another parasitoid laying egg in same prey), defend/build (if sufficient ecological pressure, e.g. risk of predation), permanently, breed
- 5, 0.5
- 5, grand-offspring
What is the sharing a nest hypothesis?
Sisters build nests … … –> … defence, separate reproduction –> one female … reproduction –> young females become …
Again, genetic predisposition:
For sisters that …, there is a benefit from raising the …’s offspring (i.e. … and …)
This may outweigh the benefit of breeding … if that is a high risk activity.
close together (due to r=constraints e.g. risk of predation), cooperative, dominates, workers
cooperate, dominant, nieces, nephews, alone
Both of these pathways have been followed by different Hymenoptera groups. … bees follow the subsoil route, where offspring stay at home and help their mother to raise subsequent broods. … and … wasps follow the parasocial route (sisters but dominant female).
Halictine, polistes, stenogastrine
… predisposes Hymenoptera to evolve sterile castes
Haplodiploidy
What is haplodiploidy?
Males arise from … eggs (…)
Females arise from … eggs (…)
Males form gametes … meiosis
Females form gametes … meiosis
unfertilised, haploid, fertilised, diploid, without, with
Therefore, daughters receive … of their father’s genes and … of their mother’s. Sons receive genes only from their ….
100%, 50%, mother (no contribution from male)
Sister-sister:
r via mother = …
r via father = …
Total r between sisters = …
- 25 (0.5 x 0.5)
- 5 (0.5 x 1)
- 75
Sister-brother:
r via mother = …
r via father = …
total relatedness = …
0.25 (0.5 x 0.5)
0 (0.5 x 0)
0.25
Brother-sister:
r via mother = …
r via father = …
total r = …
0.5 (1 x 0.5)
0 (0 x 0.5)
- 5
- look at handout/lecture for diagrams
Table of relatedness on phone
cheers from the future Joey
It is better for females to produce … than … as they are more closely related
sisters, daughters
This explains why, in social Hymenoptera colonies, all the workers are ….
females
- males are only produced for reproduction
Termites, however, are …, meaning males and females are … … to siblings and both sexes become … ….
diploid, equally related, sterile workers
- no sex bias
Aphids are …, meaning r = … and sterility is not an evolutionary puzzle due to there being no conflict over ….
clonal, 1, reproduction