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
There are conflicts between queens and workers and between workers in a colony. One of these conflicts Is the conflict between the queen and workers over the … … of their group.
sex ratio
The normal (ESS) sex ratio we see in animals is …. However, haplodiploidy and the patterns of … that it creates results in a conflict. The queen is equally related to her … and … (r = 0.5), and so favours a … sex ratio. The workers are more closely related to their … than they are to their …, so favour a sex ratio of ….
1:1, relatedness, sons, daughters, 1F:1F sisters, brothers, 3F:1M
Trivers and Hare (1976) tested the sex ratio in 21 ant species and found data that suggested that the … “won” most consistently
workers (ratio closest to 3F:1M rather than 1:1)
This may be because…
workers raise the young and can identify the sex of individuals and favour their efforts towards raising sisters as opposed to brothers as this is better for their own fitness (even if female chooses to produce 1:1 ratio)
There have been various criticisms of Trivers and Hare’s study. One of these is the potential for … … …, meaning that … may compete to mate and, since males produce lots of sperm and can potentially fertilise many females, it may be much more efficient for a female to produce a female-biased sex ratio (e.g. fig wasps) - in some situations it may be beneficial to the queen’s fitness to bias the sex ratio towards females, as well as beneficial to the workers - avoid lots of brothers competing with each other
local mate competition, brothers
The other main criticism concerns queen … …. So far we have assumed (and so do Trivers and Hare) that the queen only mates with a single male, as is the case in Myrmica rubra ants. However, this is not always the case in all species, and if the queen has more than one mate, this dramatically reduces the probability of relatedness between workers and the young that they are raising. Patterns of relatedness tend to be less extreme than we have assumed, which will have a significant impact on … … … of workers.
mating frequency, favoured sex ratios
… … are likely to be important in the evolutionary origins of eusocial species
ecological constraints (reinforced or enhanced by genetic predispositions - especially in haplodiploid Hymenoptera)
E.g. of deceptive communication: … … moth
hornet clearwing - looks like a large wasp (which are unpalatable) to avoid being eaten as it is actually very palatable
Fly and bee … are sexual mimics
orchids - deceive male flies and bees by looking like somewhat like a female so that they attempt to mate. The bee then transports pollen to another flower.
An example of infraspecific sexual deception: in the … …, males defend a territory and females visit them to spawn. Some young males look like … and are able to deceive … males and … ….
bluegill sunfish, females (satellite male), territorial, sneak matings (eject sperm over eggs)
The … spider attracts male moths by mimicking the…
bolas, female moth’s pheromone
- costly as limits spiders to only a few species of moth
Sexual selection often involves manipulation and deception - male trying to manipulate female into mating with him, e.g. using colourful displays, acoustic signals (e.g. birdsong).
can lead to arms race between the sexes
How can selection favour honest communication? Maynard Smith and Harper (2003) suggested 3 main ways in which animal signals may be honest/reliable:
- if the parties involved share a … … (e.g. honey bee communication, raven yelling, long-tailed tits)
- The display is … to perform (e.g. begging by chicks, male displays to attract females)
- Index of … (… signals) - e.g. body size/weight, volume and depth of calls
common interest, costly (known as the handicap principle), quality, uncheatable
Honest communication due to common interests: honeybee waggle dance:
Successful foragers signal to unemployed or unsuccessful foragers where food is by doing a dance (e.g. figure of 8 dance)
- common interest due to kin-selection
You know the story
Honest communication due to common interests:
Long-tailed tits
Are kin-selected cooperative breeders - discriminate between kin and non-kin using … that are individually distinctive, … (across years) and family-specific. These calls are … from carers as nestlings
- again, common interest due to kin selection
calls, repeatable, learned
Honest communication due to common interests:
Fire ants and “… …” genes
A “… …” gene causes a … effect, permits … of itself by other bearers and causes differential … towards bearers.
In fire ants, all egg-laying females are …. … females die prematurely, … females are killed by … workers. The recognition (we think) occurs by … cues on the cuticle.
- common interest due to shared genes (relatedness)
green beard, green beard, phenotypic, recognition, behaviour, Bb, bb, BB, Bb, odour
Honest communication due to common interests:
Raven yelling
- this is an honest signal between individuals that are not … (but still share a common interest)
In NA, ravens live at high latitude and are very dependent on large … in winter.
Sometimes, when ravens find a carcass, they make a very specific call
This is actually to … the defence of …-holding ravens.
- territory-holding ravens do not yell
- non-resident ravens yell
- yelling attracts other ravens to a carcass
- territory holders unable to repel many non-residents
- the number of ravens at the carcass were either very low (only territory-holders) or very high - bimodal distribution
related, carcasses (e.g. elk, bison), overwhelm, territory
Honest communication due to it being costly:
begging chicks
Parents often give … … to chicks that beg more (and raise head higher, gape more). The more food received by a chick, the higher their probability of …. Hungry chicks benefit the most from begging (larger increase in survival for same amount of food - look at graph on phone). But begging is energetically costly and costly as it can attract ….* The begging intensity of a chick is an honest signal of its need for food, due to the trade-off between the costs and benefits of begging varying with hunger (again see pic on phone).
*artificial nests more likely to be predated when begging calls played. Additionally, predation risk is higher on the ground than in trees, so ground-nesters beg more quietly and at higher … (that don’t travel as far) than tree-nesters
more food, survival, predators, frequencies
Begging is louder in chicks of birds that have a higher rate of …-… … (leading to lower …) due to lower costs of nest mates being predated.
extra-pair paternity, relatedness
Similar honest communication due to it being costly occurs in sexual display behaviours, e.g. peacocks
- bright ornamentation is costly, high quality males more likely to survive with it so those with ornamentation more likely to be high quality
- it is a handicap that only high quality males can afford
yup
Honest communication due to index of quality (uncheatable signals):
Toad calls
Deep calls in male toads is an honest signal of … and ability to … rivals
size, deter
Even body size can be cheated to some (limited) extent in certain animals, for example by inflating the …, puffing out the chest, making … … on end (e.g. in cats), elongating … to make a deeper call (e.g. red deer).
abdomen, hair stand, larynx
Intraspecific brood parasites lay eggs in clutches of …
conspecifics
e.g. European starling (only realised with the advent of genetic techniques in 1980s), burying beetle
Parental care is costly and valuable - if there are opportunities to parasitise this then we would expect evolution to select for this behaviour
Infraspecific brood parasitism is often very …. Another example is in … …, who lay an egg in their own nest, then carry it and dump it in another individual’s nest
cryptic, cliff swallows
Masked … breed in large colonies, sometime of hundreds of pairs, and it is estimated that there is a …-… rate of infraspecific parasitism. As a defence, these birds have evolved dramatic egg … allowing an individual to … its own eggs.
23-35%, divergence (colour, blotches and markings), recognise
- so brood parasitism can promote evolution (in this case divergent)
In American coots (Lyon 2003), … of pairs are parasitised. … of parasitised hosts reject at least on parasitic egg. How are these eggs recognised?
41%, 43%
Coots reject eggs that are different from their own eggs, for example in colouration (but accept eggs that look similar, even if they are parasitic)
Interspecific brood parasites lay eggs in clutches of one or more … …
host species
e.g. cuckoo, cuckoo catfish, pin-tailed whydahs (which parasitise waxbills)
… (1%) bird species are … interspecific brood parasites, including the cuckoo, meaning they never create their own nest or provide parental care.
100, obligate
Cuckoo catfish parasitise the parental care of … brooding …. The catfish deposits its own eggs within the clutch of the fish when it is spawning, before the male takes the clutch into its …. When it hatches, the young cuckoo catfish…
mouth, cichlids, mouth
eats the rest of the fish
With any form of parasitism there is expected to be a … … … between the parasite and its host due to conflicts of interests.
coevolutionary arms race
The cuckoo (Cuculus canorus) has around … main host species in Europe. The female lays 15-20 eggs per season (many more than they could if they had to raise their own offspring). They exhibit very unusual egg-laying behaviour, in that they lay their eggs in the early …, whereas most other bird species lay their eggs at …. They always lay their eggs after the host has started laying their own clutch, and remove a single host egg so that the clutch size remains the same. The egg is much … than we would expect for the cuckoo’s body size. Cuckoos can lay their eggs very … (about … seconds).
10, afternoon, dawn (to avoid carrying around all day), smaller, quickly, 10 (chickens, for example, can take several minutes)
Females … on one host species and usually lay a … egg
specialise, mimetic (egg mimics host egg)
- this is genetically determined, they can’t choose. So females are split into different lineages (called gentes)
e. g. pipit cuckoos (moorland), wagtail cuckoos, redstart cuckoos (woodland)
Why haven’t the cuckoos diverged into different species then?
Males show no specialisation or preference towards certain gentes, so maintain gene flow and prevent speciation
The cuckoo egg hatches … the host’s eggs and subsequently pushes them out of the nest. This means it becomes the … beneficiary of the parental care of the host, gaining all the food (that would otherwise be feeding 4 or 5 birds) and growing rapidly.
before, sole
- disaster for the host as it results in zero reproductive success while still facing the costs of parental care
Experimental evidence for co-evolutionary arms race (adaptations and counter-adaptations):
(Davies and Brooke) - Have cuckoos evolved in response to hosts? - Used reed warblers, a common host of the cuckoo in the UK.
Why do cuckoos wait until the host starts laying before laying their own eggs?
- found that, if they placed a model egg in each nest before the host laid, … of these eggs were rejected
- If they placed a model egg in each nest after the host had laid, … of these were rejected
Why do cuckoos lay in the afternoon?
- If placed model egg in nest in the morning, … were rejected
- if place egg in nest in the afternoon, … were rejected
- probably to avoid detection by laying at a time when hosts aren’t laying
Why do cuckoos lay so quickly?
- if placed stuffed cuckoo at nest for … mins, with model egg, the egg was rejected … of the time
- Model egg only - … rejected
Why lay a small egg?
- large (expected for cuckoo body size - 10g) model egg rejected … of the time
- usual model egg (3.4g) rejected … of the time
Why lay a mimetic egg?
- models of other common cuckoo egg mimic (e.g redstart, pied wagtail) put in reed warbler nest, all commonly rejected, reed warbler mimc egg never rejected
100%, 0%
50%, 0%
5, 45% (as warblers saw model, mobbed it, then rejected egg), 0%
40%, 0%
- all these behaviours have clear adaptive advantages
- Cuckoos have clearly evolved egg laying behaviour in response to host defences
How about counter adaptations: have hosts evolved defences in response to the cuckoos?
Non-mimetic eggs were placed in the nests of various suitable and unsuitable (for cuckoo) UK bird species. Those species that are suitable for cuckoos to parasitise, e.g. reed warbler, pied wagtail, showed…
a greater ability to reject these eggs (they more commonly rejected them). All 9 unsuitable hosts rejected 0% of the eggs. - Rejection ability has evolved only in parasitised species
(unsuitability e.g. nest in tree cavity, not feeding young invertebrates, which cuckoos need to survive)
More evidence for host evolution:
In areas of … with cuckoos (UK), host species show a much greater rejection rate (of non-mimetic eggs) than the same host species living in …. (Iceland)
sympatry, allopatry
there are no cuckoos in Iceland
We can conclude that parasitism has selected for … …, as in the absence of parasitism, the rate of this behaviour is significantly ….
egg rejection, lower
A recent observational study (Spottiswoode and Stevens, 2012) has tracked the evolutionary change in host and parasite eggs through time. This study was conducted in … and concerns the cuckoo …. and a host bird the …-… ….
Zambia, finch, tawny-flanked prinia (a species of warbler)
… of tawny-flanked prinia nests are parasitised by cuckoo finches
20%
The prinia has more … egg … than any other bird. The cuckoo finch has a … of eggs that attempts to match this. It uses several aspects of parasitic egg appearance to reject foreign eggs.
diverse, polymorphism, diversity
Clutches of these birds have been collected since the 1970s. It has been found that the mean … … between eggs has … over time, for both the host and parasite species, showing that the eggs have become more …
colour distance, diverse (greater variation now - suggests an arms race/red queen hypothesis)
Additionally, current-day cuckoo finch eggs match current day hosts better than historical cuckoo finch eggs match historical host eggs, suggesting that…
parasite eggs have tracked the evolutionary path of host eggs, rather than the other way around, as would be expected
Some species are much better at discriminating between their own eggs and a parasite’s than others. Why do mimicry and defences vary so much?
- Before parasitism - no … (eg. unsuitable hosts/ hosts in …
- Parasitism occurs and begins exploiting host- selection favours …. The level of selection depends on parasitism …. (e.g. dunnocks vs reed warblers)
- evolution of … by parasite, specialisation results in ….
- Host defences … - no parasitism, so host defence selection pressures weaken –> no rejection (as rejection may be …)
The outcome of the arms race is variable depending on many factors, including the frequency or … of the parasitism. Different species may also be at different stages of a coevolutionary arms race at any one time
rejection, allopatry,
rejection, rate,
(cuckoos lay in dunnock nests very rarely, so dunnocks are pretty shite at rejecting cuckoo eggs (weaker selection pressure), compared to species such as reed warblers who are very commonly parasitised)
mimicry, gentes
win, costly (due to recognition errors –> rejecting or damaging own eggs)
virulence
Common … have evolved … … (…) instead of egg rejection, to prevent cowbird brood parasitism
grackles, nest defence, guarding
