BIOB51 Lecture 19

What is a species (general definition)?

Smallest independently evolving unit.

What does it mean to evolve independently?

Follows its own evolutionary trajectory.

Why is defining species difficult?

Many definitions and “gray areas.”

How many species concepts exist?

20+.

What is the Biological Species Concept (BSC)?

Interbreeding populations reproductively isolated from others.

When does BSC work best?

Sexually reproducing organisms.

What is the Phylogenetic Species Concept (PSC)?

Smallest group with unique derived traits.

What does PSC focus on?

Evolutionary history.

What is the General Lineage Species Concept (GLSC)?

Independently evolving metapopulations.

What is a metapopulation?

Interacting populations of same species.

What drives speciation?

Reproductive isolation.

What happens before isolation?

Gene flow keeps populations similar.

What happens after isolation?

Mutations accumulate independently.

Result of divergence?

Formation of new species.

What are geographic barriers?

Physical separation preventing gene flow

What is allopatry?

Populations in different locations.

What are reproductive barriers?

Traits preventing interbreeding.

What keeps coral species separate?

Different spawning times.

What type of barrier is this?

Temporal isolation.

What is allochrony?

Reproduction at different times.

What species show pollinator isolation?

Monkeyflowers.

What pollinates pink flowers?

Bees.

What pollinates red flowers?

Hummingbirds.

Why does this prevent mating?

No pollen transfer between species.

What is habitat isolation?

Species live in different environments.

What is gametic incompatibility?

Gametes fail to fertilize.

What is physical incompatibility?

Damage during mating.

Why does hybridization fail in irises?

Pollen tube cannot grow.

What is hybrid inviability?

Hybrid fails to develop.

What is hybrid sterility?

Hybrid cannot reproduce.

What is ecological inviability?

Hybrid cannot survive in environment.

What is Bateson-Dobzhansky-Muller incompatibility?

Gene interactions become incompatible in hybrids.

Why does it occur?

Independent mutations in separate populations.

What happens to hybrid pollen?

Low viability.

What happens in hybrids?

Excess melanin → cancer risk.

Result of Swordtail Fish?

Reduced fitness.

Why are species definitions debated?

Continuous variation and overlap.

What reduces gene flow over time?

Isolation.

What is allopatric speciation?

Speciation via geographic isolation.

What is vicariance?

Habitat is physically split.

What is dispersal?

Population moves to new location.

Example of Dispersal?

Darwin’s finches to Galápagos.

Why do islands promote speciation?

Isolation + new environments.

What differs between populations?

Male song & female preference.

What is reinforcement?

Selection strengthens prezygotic barriers.

Why does reinforcement occur?

Hybrids have low fitness.

What evolves during reinforcement?