Phenotypic Plasticity

What is phenotypic plasticity?

The ability of a single genotype to produce different phenotypes in response to environmental cues

What are kairomones?

Kairomones are chemical cues released by one species that are detected by another species to the receiver’s benefit

Who benefits from kairomones: the sender or the receiver?

The receiver benefits; the sender does not

What organism demonstrates kairomone-induced defenses in this lecture?

Daphnia (water fleas)

Which predator releases kairomones detected by Daphnia?

Chaoborus (phantom midge) larvae

What phenotypic changes do Daphnia show in response to kairomones?

Growth of neckteeth or spines on the exoskeleton

Why don’t Daphnia always produce defensive structures?

Defenses are costly and only produced when predators are nearby

What is parthenogenesis?

A form of asexual reproduction where females produce offspring without fertilization

Which organism in this lecture uses parthenogenesis?

Aphids

What type of offspring are produced by aphids during parthenogenesis?

Only females

When do aphids primarily reproduce parthenogenetically?

During the summer months

What environmental cues trigger aphids to switch to sexual reproduction?

Decreasing temperature and shortening day length

Why do aphids switch to sexual reproduction in the fall?

To produce overwintering eggs that survive harsh conditions

What is wing induction in aphids?

The production of winged offspring in response to environmental stress

What conditions can trigger wing induction in aphids?

Crowding, predators, parasitoids, or alarm pheromones

What is the aphid alarm pheromone?

(E)-β-farnesene (EBF)

How does EBF cause wing induction?

It creates a “pseudo-crowding” effect by increasing movement and contact among aphids

What is haplo-diploidy?

A sex-determination system where ploidy determines sex

What sex develops from unfertilized eggs in haplo-diploidy?

Haploid males

What sex develops from fertilized eggs in haplo-diploidy?

Diploid females

Which insect group uses haplo-diploid sex determination?

Hymenoptera (ants, bees, wasps)

How does haplo-diploidy benefit social insects?

It allows queens to control sex ratios and colony structure

What is hybrid vigor?

Increased fitness or performance in hybrid offspring

What unusual reproductive strategy was discovered in some ants?

Cross-species reproduction producing hybrid workers

Which ants were discussed in the two-species ant story?

Mediterranean harvester ants (Messor species)

What role do hybrid workers play in ant colonies?

They function as workers and support the colony

Why is hybrid vigor beneficial in this system?

Hybrid workers may be stronger or more efficient

Why is sterility not a problem for hybrid ant workers?

Workers do not reproduce; only queens reproduce

How does this ant example relate to phenotypic plasticity?

It shows flexibility in reproductive and developmental strategies in response to ecological pressures