Speciation

Question 1

What defines a species?

Answer 1

Taxanomic, ‘biological’, evolutionary - Each has a part to play

Question 2

Please explain the Phenetic / taxanomic species concept?

Answer 2

The smallest group of natural populations permanently separated from other by discontinuity in biotype series (phenotypes dont combine) - Breeds within its own limits - Almost all species recognised like this

Question 3

Please explain the biological species concept?

Answer 3

Groups of actually or potentially interbreeding populations which are reproductively isolated from other groups.

Question 4

Explain the phylogenetic species concept

Answer 4

Smallest cluster of individuals within which there is a paternal pattern of ancestry and descent - Would lead to sub-species become species

Question 5

What are some problems with the species concept in total?

Answer 5

Hybridisation, Inbreeding, Asexual reproduction, Autopolyploidy, Chromosomal rearrangements (polyploids)

Question 6

What is the problem with species concept and inbreeding

Answer 6

Species can produce whole population of just one phenotype - If populations differ they can resemble species - Not usually permanently distinct

Question 7

What is the problem with agamospermous groups?

Answer 7

Last ability to have sex

Question 8

What are the problems with autopolyploids?

Answer 8

Look identical but aren’t - could be diploid, triploid, tetraploid…..

Question 9

What is the best species definition?

Answer 9

Species are groups of morphologically similar individuals held together due to a combination of: - natural selection, gene flow and genealogical history

Question 10

What are the mechanism contexts for speciation?

Answer 10

-Geographical / space - Time / speed (of speciation) - Genome - Ecology

Question 11

What are the two main lineages of speciation?

Answer 11

Lineage-fusion processes Lineage-splitting processes

Question 12

What are possible mechanisms for lineage-splitting processes?

Answer 12

Geographical isolation - genepool fragmentation and divergence Ecological isolation - habitat, temporal, breeding, floral divergence Genomic isolation - chromosomal rearrangemnt –> cross incompatibility, reduced fitness of hybrids

Question 13

How does allopatric (geographical) speciation occur?

Answer 13

Varied genepool –> differentiation of genepool –> physical separation of two or more large groups of the ancestral species –> divergence occurs –> uniform natural selection

Question 14

How does peripatric speciation occur?

Answer 14

Dispersal or evolution of one population of main genepool during range contraction

Divergence of new population away for ancestral species

Question 15

Define parapatric speciation:

Answer 15

When two population which are on the border / immediately adjacent diverge.

Divergence of a continous genepool

Question 16

Define sympatric speciation:

Answer 16

When a new species evolves from the ancestral species whilst still occupying the same geographical area.

Question 17

Summarise the differences between the types of speciation

Answer 17

Question 18

Explain regional speciation in terms of allopatric and parapatric models.

Answer 18

Divergence in geography thought to be primary reason.

Collective divergence- mediated by:

• unform natural selection
• geneflow between populations of diverging race, mutations spread due to adaptive value

Question 19

Evidence for regional speciation:

Answer 19

Itermediates are common in many species

Partial reproductive isolation may occur between conspecific geographical reas

No qualitative difference for trait distiinguishing between geographical area.

Question 20

Evidence against regional speciation

Answer 20

Regional genepools are usually subdivided into genetically different populations.

• Gene flow too limited to permit genepool to evolve as a race.
• Selection often causes migration opposed to evolution
• No proven examples of speciation on a regional scale.

Question 21

Explain local speciation- peripatric and sympatric models.

Answer 21

If all changes that occur with speciation occur locally then a new species can evolve by common descent if distinctive features are passed on.

Tempo and size of population can also vary

Does it depend on longevity?

single isolated populations are often not long lived enough to undergo speciation and are more likely to go extinct.

Question 22

What are meta-populations?

Answer 22

Cluster of neighbouring populations connected by frequent geneflow (including dispersal)

• longer lived than local populations
• Peripatric speciation possible?

Question 23

What mechanisms can lead to breeding system divergence?

Answer 23

Inbreeding produces two different populations

Question 24

How can floral divergence lead to speciation

Answer 24

Pollinators and flowers co-evolve

Pollinators and flower become specific to one another

Single gene may control flower colour –> what pollinators are attracted –> what diversity is produced

Two different pollinators acting on one species could lead to reproductive isolation and speciation

• DIfferent pollinators select for different variants (amount of yellow on flower)

Question 25

Summarise what speciation can involve:

Answer 25