Types of Sociality, Haplodiploidy, Eusociality: Costs, Benefits and Conflict

Cohabitation/Group Living:

Do individuals share a next or space?

Offspring Care:

Is there post-oviposition investment in offspring? Do individuals care for offspring that are not their own?

Overlap of Generations:

Do offspring remain and contribute labor while parents are alive?

Reproductive Division of Labor:

Do some individuals reproduce less or not at all?

What is inclusive fitness?

Direct fitness (own offspring) + indirect fitness (effect on relatives’ reproduction, weighted by relatedness).

What is Hamilton’s Rule?

Altruism is favored when rb > cr (cr = relatedness, b = benefit to recipient, c = cost to actor).

Group-Living and Parental Care:

Widespread (Embioptera, Dermaptera, Coleoptera, Hemiptera, Blattodea, many others).

Eusociality:

Hymenoptera (ants, bees: Halictidae, Apidae, Allodapini, wasps: Vespidae, other, Blattodea (termites), Coleoptera (ambrosia beetle), Hemiptera (aphids), Thysanoptera (gall thrips).

Independent Origins:

Roughly a dozen or more, depending on definition.

What are the three organizing features of eusociality?

Cooperative brood care, reproductive division of labor, and overlapping generations.

What is the haplodiploid hypothesis?

Workers are more closely related (r = 0.75), higher fitness to help sisters than have own offspring.

Eusociality Honey Bee:

Hymenoptera, Haplodiploid, Female workers, Holometabolous, One Queen, and Swarming.

Eusociality Ants:

Hymenoptera, Haplodiploid, Female workers, Holometabolous, Queen(s), Independent or budding.

Eusociality Termites:

Blattodea, Diploid, Both sexes are workers, Hemimetabolous, Royal Pair, and Independent Pair.

What is a caste in eusociality?

A polyphenism: one genome, multiple phenotypes, triggered by environment,

Honey Bee Castes:

Larval diet (royal jelly) → queen.

Ants Castes:

Nutrition, juvenile hormone, sometimes genetic bias.

Termite Castes:

Juvenile hormone and social cues.

What are pathways for the formation of castes in eusociality?

Insulin/TOR signaling, JH, ecdysteroids, gene expression, epigenetics.

What are the three fault lines of conflict?

Sex ratio, male production, and caste fate.

How do workers reduce conflict?

Destroy eggs laid by other workers.

How do queen pheromones reduce conflict?

Chemical signals that suppress worker reproduction.

High Relatedness:

Makes cooperation pay and cheating less profitable.

Colony-Level Selection:

Cohesive colonies outcompete fractured ones.

What is the superorganism concept?

The colony is the unit of selection, not the individual, colony-level traits (foraging, defense, thermoregulation) are the phenotypes that get selected.

What makes a superorganism?

Obligate, irreversible caste differentiation and loss of totipotency.

What are environmental drivers of flexibility?

Season length, resource availability and nest-site limitation, predation and parasite pressure influence foundress associations, temperature and elevation, caste flexibility, and mechanisms.