Predators can shape evolution in their preyUroplatus phantasticus

Dendrobates azureus

Cruziohyla craspedopus

Dermal fringes

Predator evolution pushed by prey

Thamnophis sirtalisTaricha granulosa+/- tetradotoxin

Ecologicalcontext

Resistance to tetradotoxin

Predator-prey coevolution

Predator-prey coevolutionSnakes and cane toadsBufotoxin

Brood parasites; e.g., cuckoos and cowbirds

Cuculus canorusEuropean cuckoo

Calls same

Acrocephalus scirpaceus, Reed warbler

Co-evolutionto egg rejection

Social Interactions• Actor and Recipient• Fitness possibilities (offspring units):• 1. both actor and recipient increase their

fitness: cooperative behavior • 2. fitness of actor increases, fitness of

recipient decreases: selfish behavior • 3. fitness of actor decreases; fitness of

recipient increases: altruistic behavior.

Maximizing fitness by selfish behavior

Conflict between cells and groups of cells

Slime molds: amoeboid and slug forms

Sporangium

chtA mutant Selfish behavior

Vegetative

Reproductive

Altruistic Behavior• The actor will perform an act

– places the actor at a disadvantage– benefits the recipient

• Intuitively, the fitness of the actor should decrease, and the fitness of the recipient should increase.

• Natural selection should eliminated altruistic acts.

Cooperation and Altruistic Behavior

• Slime mold• A gene for altruism • csA allele: adhesion protein• Cell differentiation in the slug• 1. Cells that form spores: DNA perpetuated• 2. Cells that form the reproductive stalk: die• Therefore, sacrifice made by some cells for the

benefit of others.

• Paradox resolved by inclusive fitness• For social animals, two categories of fitness• 1. direct fitness = personal reproduction. • But, because it is likely that relatives share some of

the same alleles…• 2. indirect fitness = assistance of actor results in

greater success in raising relatives to reproductive maturity.

• Actor’s fitness increased by an increase in frequency of alleles shared with relatives.