25 - Speciation

Question 1

What is the morphological species concept?

Answer 1

• groups of organisms that appear identical by morphological criteria
• misleading as some species mimic each other (cryptic)

Question 2

What is the biological species concept?

Answer 2

‘Species are groups of interbreeding natural populations that are reproductively isolated from other such groups’

Question 3

What are the cons to the biological species concept?

Answer 3

• doesn’t apply to asexual
• impossible to test in practice
• impossible to classify extinct taxa
• often violated - species can hybridise

Question 4

What is the null model of speciation?

Answer 4

• 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

Question 5

Give 3 examples of ‘islands’

Answer 5

• lakes and ponds
• mountain tops
• actual islands

Question 6

What is the assumption of the null model?

Answer 6

BDMIs are the only barriers keeping species apart

Question 7

What are 3 levels of pre zygotic barriers?

Answer 7

• mate recognition
• matting barriers
• postmating prezygotic - egg-sperm interaction

Question 8

Explain the affect of pre zygotic barriers and BDMIs

Answer 8

pre zygotic act earlier so contribute more to reproductive isolation than BDMIs

Question 9

Name 3 types of pre zygotic barriers

Answer 9

• temporal isolation
• host plant
• mate choice via acoustic, chemical or visual cues

Question 10

Why do pre-zygotic barriers evolve?

Answer 10

1) as a byproduct of strong divergent selection
2) reinforcement - selection against wasting reproduction on unfit hybrids

Question 11

how does reinforcement evolve?

Answer 11

• unfit hybrids are selected against
• species that so not make hybrids selected for

Question 12

Do allopathic species evolve prezygotic barriers?

Answer 12

Not really, as they are not in contact

Question 13

What needs to happen to be able to look at BDMIs?

Answer 13

incomplete post zygotic isolation