population differentiation and speciation - lecture 17 Flashcards
Biological evolution
Gentic changes in a group of organisms
Anagenesis
Evolution taking place in a single group )a lineage) with the passage of time
Cladogenesis
splitting of one lineage into two; new species arise
Sympatric speciation ( a form of cladogenesis)
No physical barrier,divergence over time
Allopatric speciation ( a from of cladenogenesis)
population diveded by a physical barrier
What is the phentic species concept?
Individuals/ populations cluster together, use this pattern to assign species boundaries
What is the biological species concept?
Use to pattern of gene flow to assign specied boundaries
what is the phylogentic species concept?
Species are on the tips on a phylogene y- they represent the smallest set of organims that share a comon ancestor and can be distinguished from other such sets
What is phylogeny?
A representation of the relatinship between groups of organisms
- typically constructed using charcters
What is a rooted treee?
Use a distantly related species to infer the ancestral state
what is an unrooted tree?
Without an outgroup , relatioship between lineages known byt not an ancestral relationship
Allopatric speciaion
speciation caused by geographic isolation
Peripatric speciation
describes speciation when a population is peripheral to a main population
parapatric speciation
speciation when populations are not isolated , but adjoinig , individuals mate locally
sympatric speciation
described speciation when populations overlap
An example of peripatric speciation
- new small population founded
- small population size(genetic drift) and selection in a new niche leads to a new species
Exampleof parapatric speciation
- continuous population without a barrier
- some contact zone with hybridization
- limited gene flow across contact zone
- usually assumes an environemntal gradient
secondary contact
lineages may split through various processes t hrough time, but then migration or lossof barriers brings them back together
