Recognition Flashcards
Why do organisms discriminate?
by recognising species, sex, sexual maturity, kin, and individuals organisms can maximise of fitness payoffs from interactions
Increase direct fitness: avoid inbreeding
Increase indirect fitness: cooperation with kin/ avoiding competition with kin
When is kin recognition beneficial and when is it strongly selected for
beneficial when:
a) Indivs likely encounter both kin and non-kin = depends on pop’n structure
b) Payoffs of kin discrimination = large
Strong selection when:
a) High cost of inbreeding-> shown when nesting pair relatedness < average population relatedness (in some cases do not get high inbreeding depression -> fungi with long haploid phase to purge deleterious mutations)
b) High risk of inbreeding (e.g. short dispersal of birds)
c) large benefit to cooperation (e.g. social insect)
d) average relatedness to neigbours/ group (e.g. Kukoborohs have high relatedness in groups so low discrimination)-> high relatedness often due to natal philopatry
This means that populations structure and costs/ benefits are shaping selection on kin recognition.
Passive kin disrimination mechanisms:
Philopatry = tendency of animal to remain in / return to particular area ensuring relatedness (if natal philopatry then area is site of birth) -> social species
Dispersal= disperse far from nest reducing chance of nesting near family (e.g.
Example: Male crab-eating foxes may disperse, establish a breeding territory close to their natal range, and, following the death of their mate, return home to tend the next generation of their parents’ cub
Example: priarie dogs
- females remain and males disperse to new group to avoid inbreeding
Mechanisms for recognition
Environmental ques -> when kin reliably associated w/ specific time or place
- Eg. female ground squirrel – low recognition in first 20 days as squirrles unable to move, and then recognition important later as squirrels gets more active
- Inflexible (can’t identify kin in other contexts)
- Vulnerable to exploitation eg. brood parasites -> Cowbird
phenotypic cues -> learning phenotypes from family member referents or self and storing information as template
Family referent matching
1) Familial recognition - learn cues carried by all members of the group
- Example: Ant alerts triggered when non-nest mate enters nest due to difference in hydrocarbon signal
2) Individual recognition- learn ques specific to individual (individuals must match all cues)
- Example: Agression higher in ground squirrel siblings when reared apart compared to reared together (even though have built up familial recognition)
When templates are sufficiently general they can be applied to unfamiliar kin.
- cichlids are able to discriminate between unfamiliar kin and unfamiliar non kin
Self referent matching (unfamiliar kin)
Compare phenotypes to self
- Example: cowbird brood parasite can’t imprint on mother feeding it as it is a parasire so inprint on self eg. if dye it black then it chooses mate that is black
- beneficial when family members are not close kin
- Example: ocellated wrasse - sneaker males have small paternity share of brood so offspring have lower relatedness to brood and should use self matching
Familial matching > self referent as recognise all allelic forms
Which phenotypes are matched?
Cues must be:
* Strongly correlated with genotype, such that high phenotypic similarity signals high relatedness
* Robust to, and detectable against, other changes associated with e.g. age, health, diet
* Variable (underlying loci must be polymorphic)
**Arthropods: **cuticular hydrocarbons
vertebrate: shared immune genes?
- MHC is present in all vertebrates (except hagfish) and are extremely polymorphic (due to selection from parasite)
- Example: fusion of adult tunicates relies on allele sharing at single histocompatibility locus (larvae preferentially settle near others matching at this locus)
- Evidence from wild population incosistent (hard to out rule other locus) and most evidence from inbred lab mice (inbred)
- also used to enhance diversity-> house nice prefer dissimilar MHC
- 3 studies show evidence of MHC odour dossortative mating -> enhance immunological resistance
Mice: Self-referent matching in wild mice is not based on MHC, but on major urinary protein (MUP) genes, plus other as-yet-unidentified genes-> important for scent crontol
Signal detection theory
Phenotypes of kin and non-kin often overlap so there must be a threshold of discrimination
Threshold location relies on:
A. relative cost of acceptances error
-> mating with relative or helping non kin
B. cost of rejection error
i. rejecting potential mate or rejecting kin
Example: Long tailed tits
- They show redirected help but need to distinguish who to help.
- However, dispersal is limited to 600m so high chance of inbreeding (avoid inbreeding using churr calls which are more familiar within families)
- Similarity between kin and non kin overlap
- Help those like non kin and breed with those disimilair with non kin
- Cost of helping non kin smaller than cost of inbreeding so threshold is shifted.
Flexible threshold:
Example: Nestmate recognition
- Start of season 40% acceptance as high cost of acceptance error -> storing food at risk of robbing
- End of season 100% acceptance as low cost of acceptance error-> large food supply so low cost of theft
Example: Egg rejection in cuckoo
- Brood parasitism occurs in second brood of redstarts
- 1st brood: low rejection rate
- 2nd threshold: more stringent threshold and high rejection
- Study compared threshold when had both eggs in nest compared to just one (higher threshold when 1 as harder to tell eggs apart)
Benefits of individuals recognition
- Can associate outcomes w/ particular indivs – learn how to respond in future
-> Eg. dominance hierarchies – best to remember who defeated you so don’t fight them again - Track particular conspecifics
-> Eg. penguin finding partner + chick in huge colony
There is a benefit to looking unusual/ more distinctive/ memorable
-> negative frequency dependent selection
Example 1: paper wasps -> less aggressive to indivs previously encountered -> rare phenotypes received less aggression
Example 2: humans -> faces more variable than other parts of body (higher diversity at face-linked loci – due to negative freq dependent selection) -> found when measuring features for army
Overview
What selects for recognition
- cost of inbreeding
- chance of inbreeding
- benefits of cooperation
- relatedness to group
Passive recognition mechanisms
- dispersal
- philopatry
Mechanisms for recognition
- environmental ques
- familiarity (individual or group)
- Self referent matching
benefits to self recognition
- associate outcomes with particular individuals
- track particular conspecific
Cues must be:
* Strongly correlated with genotype
* Robust to changes
* Variable
Signal detection theory
- threshold as non-kin kin phenotypes can overlap
- based on relative cost/ benefit of rejection error or acceptance error
