Speciation Part 2

What initiates allopatric speciation?

A reduction or elimination of gene flow, often due to physical separation.

What are two ways populations can become physically separated?

Dispersal (e.g., founder effect) and vicariance (e.g., mountain formation, new waterways).

How does genetic drift play a role in allopatric speciation?

Colonizing populations may differ from source populations due to chance, and selection may extend diversification.

What evidence supports allopatric speciation?

Evidence supporting allopatric speciation includes geographic isolation leading to divergent evolution and the presence of unique species on isolated islands or separated habitats.

What is sympatric speciation?

Speciation that occurs within the same geographic area, without physical separation. It can result from mechanisms such as polyploidy, sexual selection, or environmentally induced selection.

What are two events that can initiate sympatric speciation?

1) External events like disruptive selection based on ecological niches 2) Internal events such as chromosomal mutations.

How can sympatric populations become genetically isolated?

By developing preferences for different habitats, such as apple maggot flies adapting to apple trees.

What type of selection is occurring in apple and hawthorn maggot flies?

Disruptive selection. This occurs when two different phenotypes are favored over the intermediate phenotype, leading to the divergence of populations.

Is reproductive isolation in apple and hawthorn maggot flies prezygotic or postzygotic?

Prezygotic (host switching).

What is polyploidy?

A condition where an organism has more than two sets of chromosomes due to errors in meiosis or mitosis.

How does polyploidization lead to speciation?

It creates genetic isolation between polyploids and wild-type individuals. This reproductive barrier promotes divergence and can lead to the formation of new species.

What are the two types of polyploidy?

1) Autopolyploidy – polyploidy within the same species.
2) Allopolyploidy – polyploidy resulting from hybridization between different species.

Why is polyploidization considered a fast mode of speciation?

It can cause instantaneous reproductive isolation, making it a rapid evolutionary force.

What is an example of polyploid adaptation?

In southeastern South America, polyploid frogs outnumber diploid frogs due to environmental disruptions like temperature changes.