25 - Speciation Flashcards
What is the morphological species concept?
- groups of organisms that appear identical by morphological criteria
- misleading as some species mimic each other (cryptic)
What is the biological species concept?
‘Species are groups of interbreeding natural populations that are reproductively isolated from other such groups’
What are the cons to the biological species concept?
- doesn’t apply to asexual
- impossible to test in practice
- impossible to classify extinct taxa
- often violated - species can hybridise
What is the null model of speciation?
- if you split into two populations (allopatry)
- each population will accumulate different mutations at different loci and some will fix
- when these interbreed, the heterozygous alleles are incompatible
- BDMIs
Give 3 examples of ‘islands’
- lakes and ponds
- mountain tops
- actual islands
What is the assumption of the null model?
BDMIs are the only barriers keeping species apart
What are 3 levels of pre zygotic barriers?
- mate recognition
- matting barriers
- postmating prezygotic - egg-sperm interaction
Explain the affect of pre zygotic barriers and BDMIs
pre zygotic act earlier so contribute more to reproductive isolation than BDMIs
Name 3 types of pre zygotic barriers
- temporal isolation
- host plant
- mate choice via acoustic, chemical or visual cues
Why do pre-zygotic barriers evolve?
1) as a byproduct of strong divergent selection
2) reinforcement - selection against wasting reproduction on unfit hybrids
how does reinforcement evolve?
- unfit hybrids are selected against
- species that so not make hybrids selected for
Do allopathic species evolve prezygotic barriers?
Not really, as they are not in contact
What needs to happen to be able to look at BDMIs?
incomplete post zygotic isolation
