When a population is divided into geographically isolated subpopulations.
Deme
local population/subgroup where phenotypic variations reflect local environmental factors. There is limited gene flow between groups.
Cline
Geographical gradient in the phenotype of individuals of the same species. Often occurs in relation to changing altitude or latitude.
Sympatric Speciation
Gene flow that is prevented by a mechanism that is not geographic separation.
When is Allopatric Speciation Complete
When the isolated populations can longer produce viable or fertile offspring
Polyploidy
Increases the number chromosome sets, leading to reproductive isolation. A common cause of sympatric speciation, especially in plants.
Disruptive Selection
Can to lead to sympatric speciation by favouring extreme traits
Niche Differentiation
Can promote sympatric speciation when different groups within the same population adapt to distinct ecological niches.
Where is Sympatric speciation common
Environments with diverse resources where ecological opportunities allow different groups to exploit different resources.
Genetic Divergence
In allopatric speciation it occurs due to geographical barriers. In sympatric speciation it occurs due to differences in niche specialisation or behavioural isolation.
