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