4. The Geography and Ecology of Speciation Flashcards
What are the three major forms of speciation?
Allopatry, Parapatry, Sympatry
Each form is characterized by drift, selection, gene flow, and mutation.
Define allopatric speciation.
Geographic separation leading to lack of gene flow
Can be vicariant or peripatric.
What is vicariant speciation?
Separation of two populations via an extrinsic, geographical barrier
A form of allopatric speciation.
What is peripatric speciation?
A small group of individuals breaks off from the main population
Another form of allopatric speciation.
Define parapatric speciation.
Speciation with adjacent ranges and some gene flow
Leads to neighbouring sister species.
Define sympatric speciation.
Speciation occurring in the same area with strong divergent selection
Usually requires some geographic speciation beforehand.
What is the significance of geography in speciation?
Provides the stage for evolution and influences gene flow
Geography limits gene flow and affects evolutionary processes.
What type of speciation is most common in animals?
Allopatric speciation
Most common in plants is sympatric speciation.
What is ecological speciation?
Divergence due to divergent natural selection between different environments
Barriers to gene flow evolve as a result.
List examples of selective pressures in ecological speciation.
- Abiotic
- Biotic
These pressures are often hard to measure.
What methods can be used to study ecological speciation?
- Reciprocal transplant experiments
- Measuring directional selection on traits
- Analyzing adaptive landscapes
Examples include studies on monkey flowers and Darwin’s finches.
What are some reproductive barriers in ecological speciation?
- Divergent habitat preferences
- Immigrant inviability
- Ecologically-dependent selection against hybrids
- Sexual isolation
Additional barriers include post-mating incompatibility and intrinsic hybrid incompatibilities.
What is mutation order speciation?
Evolution of reproductive isolation by chance fixation of different alleles
Occurs despite similar selective pressures.
What mechanisms contribute to mutation-order speciation?
- Intragenomic conflict
- Transposons
- Low hybrid fitness
Example includes cytoplasmic male sterility in Mimulus hybrids.
Compare ecological and mutation-order speciation regarding natural selection.
- Ecological speciation: ecologically-based and divergent
- Mutation-order speciation: concordant
These differences affect isolation mechanisms.
How does ecological speciation relate to gene flow?
Can proceed with or without gene flow
Mutation-order speciation requires no gene flow.
What role does standing genetic variation play in ecological speciation?
Large role
In mutation-order speciation, standing genetic variation is less important.
