Speciation

Question 1

What is a species?

Answer 1

Populations between which there is no or very little gene flow

Question 2

What is speciation?

Answer 2

Origin of reproductive barrier among population that permit the maintenance of genetic and phenotypic distinctiveness in geographic proximity

Question 3

What are the three ways allopatric speciation can occur?

Answer 3

When a core species colonise new habitat.
When a continuous distribution gets fragmented (e.g. island chains, like Drosophila flies in Hawaiian archipelago).
Ring species: where the middle is unsuitable, colonise as they move round, when come back two separate species

Question 4

What is an example where ring species have occurred?

Answer 4

Eurasian Greenish Warbler, multivariate statistical analysis, shows large change in song characteristics, no longer recognise each others songs.

Question 5

Who suggested allopatric speciation was the main driver of speciation?

Answer 5

Ernst Mayr

Question 6

What would we expect to see in real world data if allopatric speciation holds?

Answer 6

Anciently derived sister groups to have overlapping regions because sufficient differences have occurred so that they are able to inhabit the same areas without the gene flow collapsing), more recently derived groups have non overlapping regions.

Question 7

What are the Nerodia snakes?

Answer 7

Snakes in N. America. Have polymorphic colour variation depending on habitat. Limestone areas are plain whilst areas high in vegetation are banded. The mainlaind is 100% banded, as you start to move towards the islands plain more frequent but still intermediates and banded ones, why no fixation becuase ongoing movement from mainland to island, continual gene flow!

Question 8

How did oil seed rape come about?

Answer 8

Ploidy speciation

Question 9

What two veg where used, how many chromosomes did they have?

Answer 9

Cabbage (18) and turnips (20)

Question 10

Why were the two vegetable sterile at first?

Answer 10

Because they had odd number of chromsomes but a failure of meiosis results in new plants with 38 chromosomes.

Question 11

What is anagenesis?

Answer 11

Speciation without splitting. Change through time. No division of lineages. Accumulation of changes within same lineage so if we take samples from different time points there would be sufficient genetic differences that we’d consider them separate species.

Question 12

What is sympatry?

Answer 12

When species are within cruising range of one another

Question 13

Who suggested sympatric speciation might occur?

Answer 13

John Maynard Smith

Question 14

How did John Maynard Smith say that sympatric speciation could happen?

Answer 14

When you have two slightly different niches and different alleles are favoured at either one

Question 15

What idea does sympatric speciation rest on?

Answer 15

Genotype fitness landscape

Question 16

What is an example of ecological speciation?

Answer 16

Sparkleberry/apple maggot fly. Found from Mexico up to US breeds on fruit of several trees, apple, sour cherry, hawthorn. Different forms specialise on to different host plants. Conditions that would favour reproductive isolation due to different emergence times of larva. (fruit in different seasons) reduces chance of contact.

Question 17

How did ecological speciation occur?

Answer 17

Was continuous then fragmented. Changes on chromosomes 1-3 that are associated with diapause and emergence times. Fly is polymorphic for different emergence times. 150ya explosion in agriculture and orchard development so new potential hosts to be exploited by the flies with the relevant polymorphisms. Allopatry a while ago and introduction of new host resource to facilitate sympatric speciation

Question 18

What is another example of sympatric speciation?

Answer 18

Threespine stickleback in N.America. benthic form chunkier more armouring, Limnetic less so, habitats surface whilst benthic inhabits the deep bit. In each habitat different resources drive divergence and phenotypic difference. If they do meet and breed offspring have poor fitness as phenotype will not be specialised to either habitat

Question 19

What are pre-zygotic barriers?

Answer 19

Arise from being in different habitats, from phenological source, reproducing at different times of year. Sexual isolation

Question 20

What are post-zygotic barriers?

Answer 20

Occurs after mating, after hybrid offspring are generated, selection against migrant and hybrids because phenotype has lower fitness in habitat

Question 21

What is post?

Answer 21

Barriers arise due to genetic incompatibilities