Degree to which individuals in a population associate
Sociality
Degrees of Sociality:
solitary behavior
interactions limited to competition and copulation
Degrees of Sociality:
Subsocial behavior
Protect/feed their offspring
leave before offspring become adults
Degrees of Sociality:
Eusociality (highest degree of social organization) categorized by three traits:
1. Cooperative care of young
2. Overlapping generations in the
same colony
3. Division of labor between castes
Social Adult Females Hymenoptera are
holometabolous
larvae rarely contribute to colony welfare
superorganism
Social Bees
are what?
1000 species of Apoid bees that are eusocial
highly social = honeybees
Primitively eusocial: bumblebees and sweat bees
Apis mellifera is most known for
social insect (honeybee)
Ants are known for
25% of terrestrial animal biomass
Exclusively eusocial
Superorganism
Individual functions as part of a colony,
exhibiting attributes
of an organism
Superorganism:
Environemental success is a result of
cooperative group behavior
Evolution of Eusociality:
Eusocial colonies have a
solitary common ancestor
Evolution of Eusocial Behavior
A critical transition from subsocial to eusocial involved to transition to
nonreproductive castes
Evolution of Eusocial Behavior
Sterile indivduals are altrustic sacrifice their
reproductive ability to benefit the colony
- act on inclusive fitness
Inclusive fitness
ability to pass genes on to next generation including shared genes passed on by relatives
Why be Eusocial
Safety and the numbers
Caste System:Queen
Characteristics
- functional reproductive female
- larger than workers with long abdomen
- pheromones to prevent production of another queen
- Spermatheca capable of storing sperm for her entire life
Division of labor
Caste systems are dependent on this
colony size which is an important attribute of evolution of behavior and labor
Caste system: Drones
Characteristics
- Males are sexual forms not caste
- winged with a developed thorax and compound eye
- Fed by workers; dont work
- Haploid
Caste System: Workers
Characteristics
- numerous members
- divided into subcastes based on size
- sterile females with no ovarioles(wings/flight muscles)
Monomorphic Workers
not specialized to do specific tasks
Polymorphic workers
variation of different sizes that exist in the same colony
Temporal Castes
Plasticity where workers revert task based on
colony need
Temporal Castes
More Characteristics:
Division of labor within workers consistent with aging
Progress from tasks inside nest to outside
Evolution of Eusociality Signals
- Anti-mating signal (solitary ancestor): Ovarian activity linked to cuticular profile changes
- Dominance signal (facultative eusocial): Most fertile female shows strongest signal; others disperse or help
- Queen signal (eusocial): Ovarian activity becomes an honest signal; others become workers
Hamiltons Rule & Kin Selection
Altruistic allele (drive for eusocial behavior) could increase in frequency if the condition were satisfied:
rB>C
- genes increase in frequency = genetic relatedness
B = benefit to recipient
C = Cost to actor
r = relationship coefficient of relatedness between B & C
Hamiltons Rule & Kin Selection
Proposed two mechanisms for kin selection
1. Kin recognition allows individuals ability to identify
relatives
2. Dense populations, slow movement of organisms from
place of birth, local interactions are among relatives
Kin Selection
Acts on inclusive fitness explained by
considering genetic
relationships where
Son share 50% mother genes
Daughters share 50% mothers' genes
Sisters share 75% of genetic material
Kin Selection: Haplodiploidy
Charactersitcs
- mating system
- eggs develop into females and unfertilized into males
- females are dip and males hap
Relatedness
The assumption that was needed for kin selection
high degree of relatedness
- ecological parameters should be measured
high relatedness = participate in altruism