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3rd year - Social evolution > Group formation, maintanence and transformation. > Flashcards

Group formation, maintanence and transformation. Flashcards

1
Q

definition of a social group

A

stable group of any entities that cooperate in
ways that make the group a potential candidate for consideration as an individual. (similar to a temporary aggregation, eg flock/herd, although these arent stable)

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2
Q

3 stages of social group

A
  1. formation
  2. maintanence - often conflicts arise and goes back to individuals
  3. transformation - adaptations arise, individual entity.
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3
Q

define social group formation

A

processes involved in the origin of social living

initial spread of genes for social behaviour through a pop of initially non social organisms

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4
Q

what is the formation stage for each of these major transitions?

  1. separate unicells to a symbiotic unicell
  2. unicells to a multicellular org
  3. multicellular org to a society
A
  1. separate unicells to a symbiotic unicell
    formation: origin of EK cells
  2. unicells to a multicellular org
    formation: origin of multicellular orgs.
  3. multicellular org to a society
    formation: origin of societies
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5
Q

define a ‘pathway’ in social group formation

2 pathways

A

stages through which social groups pass as they first arise.

  1. Unrelated partners/egalitarian, can be ope or closed
  2. Related partners/fraternal
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6
Q

factors are what?

3categories of factors

A

what drives non social characters together in the first place.

  1. Genetic - relatedness, shared rep fate, eg social partners each transmit genes from parent to offspring in the same propagule.
  2. Ecological - features of external environment
  3. synergistic - features inherent in group organisation. group members work together to acheive something new.
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7
Q

what are open and closed pathways for unrelated partners

A

open - new partners are needed every generation. eg M and F genomes in sexual rep, symbiosis btw bobtail squid and vibrio fischeri.

closed - partners remain together across generations, eg mit and chloroplasts in EK cells.

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8
Q

examples of mutualisms which have open and closed pathways

A

open - Macrotermes sp. termites, every new termite nest uses new fungi found in the environment.
Bobtail squid and vibrio fischeri,

closed - ants, Attini sp. new nests use fungal innoculum from old nest .

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9
Q

describe genetic factors for non relatives

A

since non relatives, aligned fitness interests cant arise through shared genes, so must arise through shared rep fate. eg social partners transmit genes from parent to offspring in the same propagule.

eg host protoeukaryoticcell engulfd PK cell and divides, daughter cells have copy of host and bacterial genome. IF of both maximised by increased number of descendent cells.

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10
Q

describe ecological factors for non relatives

A

comparative work suggests mutualisms are more likely in tropical environments - greater sp richness, greater stability and persistence.
if species are sessile - major benefits for dispersal and nutrient gain

unlikely there was an ecological factor causing origin of ek cells and sexual rep, as there is a huge diversity of mutualistic interactions.

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11
Q

synergistic factors for non relatives

A

Sharing of functions
likely to be key element of the origin of sociality.
many mutualisms are based on the exploitation of biochemical abilities of PK.

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12
Q

what two types of pathways can relatives have?

A

Subsocial - non dispersing offspring associate with parents. this guarantees relatedness among social partners.
Semisocial - same generaion orgs associate - groupinfs of relatives or non. relatives more common.

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13
Q

describe some good experimental evidence for the subsocial pathway.

A

Boraas et al 1998
Exp evo of multicellularity
1. Chlorella vulgaris, green alga, Obligately asexual, 5–6 μm diameter, Unicellular
2. Added Ochromonas vallescia, larger pred unicell.
3. witnessed evolution of clusters of Chlorella vulgaris. initially 10-100 cells, eventually left at 8 cell formation. hertiable even after removal of predator.
suggested due to daughter cells failing to break out of parental cell wall following cell division.

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14
Q

5 examples which have formed groups by the subsocial pathway?

A 
meerkats
superb fairy wrens
nakedmole rats
wild dogs
pied babblers
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15
Q

what is a possible cause of multicellularity via semisocial pathway?

A

development of multicellularity by the aggregation of cells.
likely in terrestrial environments
in aquatic enviro, chemicals causing aggregation get more dispersed.
eg slime moulds, myxobacteria.

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16
Q

some genetic factors towards the subsocial pathway for relatives

A

high relatedness coupled with a single cell propagule causes evo of multicellularity

high relatedness coupled with a single monogamous colony founding pair causes sociality. eg 35% foundresses in polistes wasps are non relatives although still have quite a high relatedness of 0.21-0.43.

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17
Q

some genetic factors towards the semisocial pathway for relatives

A

if within group relatedness is positive, promotes altruism.

eg myxobacteria. Kin discrimination and active exclusion of genetically dissimilar cells from aggregation.

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18
Q

some ecological factors for relatives

A

Predation
Food supply
nest site limitation

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19
Q

How does food supply promote sociality?

A

Food supply - food shortage selects for larger size of alga: Volvox carteri for increase in nutrient uptake rate and nutrient storage.
in carrion crows, extra food increased nondispersal and increased helping behaviour

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20
Q

how does predation promote sociality?

A

Predation - Chlorella vulgaris
experimental predation lead to multicellularity
In cichlids, seen that predation reduces helper dispersal, and groups better protected. field manipulation in lake tanganyika.

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21
Q

how does nest site limitation promote sociality?

A

eg Paper wasp (Mischocyttarus mexicanus)
eperimental removal and addition of nests.
removing nests drives grouping, adding nests drives solitary nesting.

22
Q

synergistic factors for relatives.

A
  1. locomotary advantage: Larger slime moulds slugs move faster. Larger salps use less energy swimming as a group.
  2. foraging advantage: Slime moulds - shed amoebae from migrating slugs to reach inaccessible food. African wold dogs increase prey size, capture success and food per individual with increased group size.
23
Q

definition of group maintenance

A

proesses that ensure stable group persistence
following establishment

maintain group stability once formation has occurred.

24
Q

general threats to social groups

A

Threats from outside
threats from within
Personal investments by group members

25
Q

what does successful limitation of exploitation by outsiders entail?

A

recognition of self vs non self
exclusion of non self.

this is between group kin discrimination

26
Q

what cues are used in limiting outside threats?

A
  • recognition of intrinsic genetic cues - allorecognition
    eg sessile colonial marine invertebrates reject genetically dissimilar conspecifics.
  • learning of cues of self through early exposure. eg Vertebrate immune system
27
Q

describe cues used by long tailed tits to recognise relatives?

A

long tailed tits form groups early in breeding season, if fail to breed the first time will help others, usually relatives. recognition by learning call of parents and nest mates to distinguish between relatives.
cross fostering exp showed call recognition was purely learned, not innate.

28
Q

example of how ants recognise their own workers from outsider workers.

A

Formica exsecta
wprkers forage and return to nest,so must be recognised as own and not outsiders. use chemical cues.
exp by manipulating chemical component on live ants.
extracted chemicals from cuticular hydrocarbons and used synthetic blends to test aggression.
found colony specific alkene signature on cuticle. workers attack those with different signature.

29
Q

why aren’t recognition systems not perfect?

A

cues from different categories are likely to overlap
there is an arms race between hosts and exploiters.
can have either of 2 extreme thresholds, in which a) some outsiders are let in but no self are excluded. b) all self are let in along with some outsiders.
in reality, there is a middle ground which varied between groups.

30
Q

how have some parasites adapted to exploit the cue detection in self recognition?

A

chemical mimicry

adoption of recognition compounds

31
Q

why are cheats under negative frequency dependence?

A

Groups with more cooperators outcompete groups with more cheats.

cheating is self limited by negative effects on:
fertilisation success (eg cytoplasmic male sterility)
group survivorship or productivity.

32
Q

demonstration of negative frequency dependence in pseudomonas fluorescence.

A

if left unstirred in beaker, lab evo of ‘wrinkly spreader’ cells forming a multicellular mat by adhesive polymer. this is altruistic because some cells give up rep to form mat, but gives greater access to gaseous O2.
cheats are smooth mutant cells which still rep and join mat. more cheats = earlier collapse of cell mat.

33
Q

describe Cape Honey Bee cheating neg freq dependent regulation

A

workers rep asexually, not just the queen. associated with dominance behaviour, when reproduce, stop acting like a worker - ‘cheating’.
experimentally: bred colonies with different proportions of reproducing workers.
100% dominant workers
50/50 sub/dom workers
100% subordinate workers.
found that productivity (brood rearing, comb building, syrup holding) decreases with more cheats and colony eventually collapses. Cheats lose out on IF benefits because the queen cannot reproduce so eventually it doesnt pay to cheat.

34
Q

how is exploitation by insiders limited?

A

coercion
may force other group mambers to act cooperatively.
eg enforced uniparental inheritance of mitochondria, driven by parental genomes.
if inherited mit form both parents, would be immediate parental conflict, as the organelles dont have perfectly aligned interests.
mammalian male genome tags all mit in sperm with a dormant protein. when zygote forms 8 cells, protein is activated, killing all male mitochondria.

35
Q

2 examples of coercion to make parties act cooperatively at a cellular level

A
  1. enforced fairness in meiosis.
  2. Sex ratio distortion - organelles related by 1 to female and 0 to male. causes male killing intracellular bacteria, harboured by females. resulted in evo of supressor genes to counteract female forces.
36
Q

2 more eg of coercion at an individual level

A
  1. dominance, punishment and policing in societies
  2. enforced fairness in interspecific mutualisms. eg cleaner wrasse - Labroides dimidiatus. cleaners remove parasites and dead tissue, cheat be feeding on live tissue. Fish monitor cleaner beh - avoid cleaners they have seen cheating. therefore cleaners can only cheat at a low level, and cheating interactions depends on clients too, if regular clients, then less cheating.
37
Q

def of group transformation

A

processes that turn stable social groups into more cohesive, integrated entities

ie conversion of groups which have undergone social maintenance into those which could be regarded as individuals.

38
Q

examples of simple and complex groups

A

simple: cellular slime moulds, small volvocine algae.
Complex: fungi, plants, animals

39
Q

examples of simple and complex societues

A

simple: halictid and allodpine bees
coop breeding vertebrates
Complex: nakedmole rats, many ants and termites.

40
Q

how does reproductive division of labour differ between simple and complex multicellular organisms and societies?

A

low division of labour in simple MC orgs (degree of dimorphism btw germ cells and soma) and societies (dimorphism btw queens, workers, helpers).
high division of labour in complex.

41
Q

what is the most complex eusocial vertebrate society?

A

Naked mole rats.

breeding females have longer vertebrae, which only elongates when she becomes the queen at first pregnancy.

42
Q

how does non-reproductive division of labour differ between simple and complex multicellular organisms and societies?

A

simple MC orgs - few somatic cell types
complex MC orgs - many somatic cell types.
simple societies - few morphological castes among workers
complex societies - many morphological worker castes.

43
Q

how does body size differ btw simple and complex MC orgs and societies?

A

MC orgs - simple = few cells
-complex = many cells.
societies - simple = few workers
complex - many worker types

44
Q

evidence for link between size and complexity

why?

A

larger ant colonies have a greater degree of worker polymorphism.
increases efficiency if individuals specialise in different tasks. in more complex societies, cannot switch between tasks. this is a causual relationship.

45
Q

what causes the link between size and complexity?

in both MC orgs and societies.

A

likely to be an external driver of size.
Short term ecological factors: protection from predators
increased nutrient uptake and storage, increased mobility and dispersal, resilience to environmental stressors.
societies: short term ecological factors
protection from predators
food supply
capacity to monopolise high quality sites
resilience to environmental stressors.

46
Q

study of colony size and success.

A

Adams and Tschinkel 2001.
Red imported Fire Ant.
Tracked field monogynous colony over time. bigger colonies more likely to survive.
field manipulation - 12 plots, removed all existing colonies in 6 plots, found colonies expanded to fill available niches.
Selection for success in intraspecific comp could drive increased group size.

47
Q

what are some long term evo processes which externally drive increasing group size?

A
  1. Arms race between different lineages in the same taxon. eg ants and termites may be competing - evolved at the same time and competition could drive enormous group size.
    trees - compete by growing taller.
  2. complex groups may pass a point where cant return to solitary living. Taxa near origin of eusocialty can switch between group and solitary whereas eusocial groups cannot.
48
Q

why is there often an optimal size for groups?

A

bigger may be beneficial in some respects but costly for other things.
eg larger lion prides - greater capture success, but less food per lion. greater territory defence and defence of young.

49
Q

how does increased size allow increased robustness?

A

bigger groups are buffered against loss of specialists,

50
Q

what are some physical constraints of increasing size?

A

in MC orgs:
if small, large SA:V ratio, so passive diffusion is sufficient.
larger - reduces SA:V, so active transfer needed as well as more specialised structures, more somatic cell types.
constraint on size drives specialisation.

51
Q

why may humans have stalled in a major evolutionary transition towards eusociality?

A
  • the boundaries of biological populations and major cultural groups are no longer congruent.
  • as communication and trade expand, individuals involved in networks of relationships outside of the local group.
  • within groups, individuals belong to institutions eg economic, religious, which dont perfectly overlap.
  • as groups grow larger, freq of selective events involving groups decreases.

3rd year - Social evolution (6 decks)

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