Evolution Final- Speciation

Process of allopatric speciation

1. Barrier appears and creates geographical isolation 2. Events in isolation 3. Events and outcomes of secondary contact

Events of allopatric isolation

1. Geographical barrier 2. Founder effect and size of population 3. Increase gene flow and limited gene flow 4.Environment changes 5. Time for divergence short and long 6. Secondary contact

Allopatric events secondary contact

1. Interbreeding occurs and produces fertile and vigorous offspring 2. Interbreeding occurs and produces fertile but reduce vigor offspring. Hybrid offspring is not attractive. 3. Interbreeding does not occur, but produces offspring from forced matings that are fertile and viable. 4. Interbreeding does not occur and offspring from forced matings are infertile or die before developing.

Factors for parapatric speciation

1. Occurs when there is a sudden change in the environment over geographic barrier 2.Disruptive selection counteracts gene flow (strong) 3.Population is not randomly mating 4. Hybrids have low fitness in both parental areas 5. Each parental form has high fitness in its own environment 6. Reproductive barrier

Evidence for allopatric speciation

1. Relationship within between species geographic and genetic distances among continuous and discontinuous populations 2. Local adaptation and historical traits 3. Mate recognition systems among population of the same species with increasing geographic isolation 4. Relationship of genetic similarities and time separation of populations and species

Factors for sympatric speciation

1. Strong disruptive selection within populations for traits associated with alternative resources 2. Strong selection against hybrids formed from mating of individuals specializing on alternative resources 3. Strong feeding preferences on alternative resources 4. Strong preference for nesting resources where its fitness is the highest 5. Strong linkage between resources use and resources choice

Sympatric mechanism

1. Strong ecological isolation 2. Strong disruptive selection

Types of classic models speciation

1. allopatric speciation 2.sympatric speciation 3. parapetric speciation 4. peripatric speciation

Factors promoting allopatric

1. complete geographic isolation 2. small size population 3. different selective environment 4. sufficient time in isolation

Allopatric geographic barriers

CAUSES EMPHASIS ON PHYSICAL AS OPPOSED TO RESOURCES: 1. Intrusion barrier ( liquid rock that forms under Earth's surface-magma) 2.Bifurcated (division colonization of new geographic range) 3.Invasion of isolated mountaintop habitats 4.Stranding (formation of continents) 5. Colonization of Oceanic islands 6. Land mass separation

Founder Effect

Founder effect is the loss of genetic variation that occurs when a new population is established by a very small number of individuals from a larger population.

genetic drift and natural selection

Make different populations different from each other. Results in population differentiation and and speciation.

gene flow

Reduces chance of speciation and make populations to look similar to each other.

Speciation

The evolution of two or more new species arise from one pre-existing species.

allopatric speciation

____ is a speciation that occurs in the absence of gene flow. New species are geographically isolated. This arises due to drift and local adaptation. Due to founder effect the genetic structure population 1 is not equal to population 2. Gene flow not possible because of geographical barriers.

parapatric speciation

____ is a speciation that occurs when populations are geographic neighbors and, migration and gene flow suddenly happens between them. Variation evolves at the edge of range. Similar to sympatry.

sympatric speciation

____ is a speciation that occurs when populations evolve to be separate species in the same geographic area. This occurs due to adaptation to different aspects of range (ecological areas). Genetically polymorphism. Different groups in same geographical area but don't contact each other because of ecological differences.

peripatric speciation

____ is a speciation that occurs when populations goes through a strong selection from invasion of different habitats. Genetic drift becomes important in small populations and plays role in speciation. Similar to allopatry except the divergent population is small. Gene flow not possible because of geographical barriers.