Lecture 6: Units of Selection continued
Most Extreme example of Kin Selection:
EUSOCIALITY
Eusociality:
1) Overlap in generations
2) Co-operative brood care
3) Specialized castes of non-reproductive
individuals
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Kin Selection - Evolution - Lecture Slides, Slides of Theory of Evolution
Kin Selection, Units of Selection, Overlap in Generations, Eusociality, Plant Galls, Haplodiploidy, Unfertilized Eggs, Favours Reproduction, Species Queens, Parental Manipulation are the key important points of lecture slides of Evolution.
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Lecture 6: Units of Selection continued
Most Extreme example of Kin Selection:
EUSOCIALITY
Eusociality:
Overlap in generations
Co-operative brood care
Specialized castes of non-reproductive individuals
Examples
Hymenoptera
(bees, ants, wasps)
Isoptera
(termites)
Mammalia
(naked mole rats) How did this evolve?
Haplodiploidy
- Eusociality is COMMON in haplodiploid hymenoptera (evolved 11 times)
- UNCOMMON in diploid ( only 1 time)
Haplodiploidy
Diploid ( 2n ): produce ova by MEIOSIS females from fertilized eggs Haploid ( 1n ): sperm by MITOSIS males come from unfertilized eggs
focal individual: female 0.5 0.5 0.75 0.5 0.5 0. male 1 1 0.5 - - 0.
relative mother daughter sister father son brother
Favours reproduction of sisters over all others Docsity.com
Hypothesis 2: Parental
Manipulation
• Queen suppresses reproduction of other
workers
• Chemical cues
• Physical inhibition
• Lots of experimental support
Specialized Castes
- Queens & Workers
Fertilized egg
Worker Queen
Royal Jelly
Royal Jelly – hormones that affect development of tissue including ovaries
Hypothesis 3: Mutualism
- Worker manipulation?
- Cryptic reproductives
- Greater fitness by helping rather than founding a new colony.
- Unmated workers lay haploid eggs in many species.
Most likely…
Eusociality ONLY occurs in species with:
- Complex nests
- Larvae cared for extensively
Thus, females are unlikely to be successful if breed on their own.
Ecological not genetic?
“Best of a bad situation”
Normal Mendelian Segregation
- Alleles segregate in a 1:1 ratio in gametes produced by heterozygotes
- Meiotic Drive: non-random segregation of alleles into gametes
Aa
A
a
50%
50%
Segregation Distorters
- Drosophila spp.
- sd prevents dev’t of sperm with + allele
- sd/+ have low fertility
- sd has advantage: genes at other loci suffer
- selection for suppressors & recombination
sd/+
sd
90%
10%
B Chromosome
- all other chromosomes in sperm supercondense so lost in mitosis
- sperm carries only B chromosome
- sperm empty of all other genes than PSR
Ultimate ‘selfish gene’ : copies itself while destroying all other genes !!
Intragenomic Conflicts
SOMA
Mutations die out
GERM LINES
Mutations inherited
some alleles gain fitness at the expense of genes at other loci
If somatic lines give rise to germ cells selection for cell lines
Heritability
- Proportion of variation in a phenotype in a population attributable to individual differences in genotype
- Related to the genetic & phenotypic makeup of a population
Heritability
HIGH
LOW
e.g. Eye colour
e.g. Number of eyes