Speciation

Question 1

what is the morphological species concept

Answer 1

The Morphological Species Concept - distinguished by visible phenotype

Question 2

what is the Ecological Species Concept

Answer 2

Ecological Species Concept - distinguished by ecological niche

Question 3

what is the Biological Species Concept

Answer 3

Biological Species Concept (BSC) - distinguished by reproductive isolation; groups that do not interbreed are considered different species.

Question 4

what are the 3 main species concepts

Answer 4

Morphological
Ecological
biological

Question 5

what does Allopatry refer to

Answer 5

Allopatry refers to populations which are geographically separated

Question 6

what is allopatric speciation

Answer 6

Allopatric speciation: local adaptation (Natural selection), mutation, and genetic drift, results in initially indentical populations diverging phenotypically and genetically.

Overtime, incompatibilities (genetic, behavioural, etc) accumulate, such that even if they ‘meet’ again (secondary contact) they no longer interbreed

Question 7

what is Sympatric Speciation

Answer 7

Sympatry refers to populations which co-occur geographically

Sympatric speciation: thought to be less common than allopatric speciation, but possible if there is fine scale separation in space or time

Question 8

how does Geneflow play into speciation

Answer 8

The key in both models is reproductive isolation, the reduction or absence of gene flow.

Gene flow counteracts the formation of species and, in general works against local adaptation.

Question 9

what is the expectation regarding hybrid when the cause of initial divergence is local adaptation

Answer 9

If the cause of initial divergence is local adaptation, the one expectation is that hybrid offspring suffer low relative fitness compared to offspring of ‘pure’ crosses

i.e. natural selection against hybrid phenotypes (post-zygotic barriers)

Question 10

what can species evolve to reinforce speciation

Answer 10

But species can also evolve mechanisms of ‘reinforcement’ potentially reducing the likelihood of making hybrids at all.

e.g. if mating preferences (pre-zygotic) evolved to minimize the risk/costs or producing unfit offspring (postzygotic)

Question 11

what is microevolution

Answer 11

The forces of evolution explain changes along each branch aka “microevolution”

Question 12

what is Macroevolution

Answer 12

Where do new species come from?

The emergence of new species is “Macroevolution”

Question 13

what is speciation

Answer 13

Speciation is a reduction of gene flow which leads to new species.

Speciation preserves the history of microevolution. The shape of the Tree of life is determined by speciation and extinction.

Question 14

what do Phylogenetic trees allow estimation of

Answer 14

Phylogenetic trees allows the estimation of diversification rates (net number of species)

Question 15

how long are the intervals between speciation ‘events’

Answer 15

intervals between speciation ‘events’ can range from 4,000 years to 40 million years in various taxa.

The average is 6.5 million years.

Question 16

how many genes are involved in speciation

Answer 16

Speciation can involve many or few genes

Question 17

what is the difference between Allopatric and Sympatric speciation

Answer 17

Allopatric speciation involves geographic barriers while sympatric does not

Question 18

what prevents speciation

Answer 18

Gene flow counteracts the formation of species and in general works against local adaptation.
So for speciation to occur, Gene flow must reduce.

Question 19

what are 8 barriers to gene flow

Answer 19

There are ~8 types of barriers which can prevent gene flow:

1. Habitat Isolation
2. Temporal Isolation
3. Behavioural Isolation

mating

4. Mechanical Isolation
5. Gametric Isolation

fertilization

6. Reduced Hybrid viability
7. Reduced Hybrid fertility
8. Hybrid Breakdown (breakdown of hybrids in later generations)

1-5 are Prezygotic

6-8 are Postzygotic

Question 20

describe incomplete reproductive isolation

Answer 20

Depending on the strength of the barrier (including selection against hybrids) and the amount of gene flow, Speciation can still proceed despite Hybridization

Incomplete reproductive Isolation is quite common in natural population

Question 21

what are the 3 possible outcomes from Hybridization between 2 lineages:

Answer 21

There are 3 possible outcomes from Hybridization between 2 lineages:

1. Reinforcement: the hybrids are less fit and speciation is reinforced
2. Fusion: the hybrids are more fit and two lineages merge back together
3. Stability, both species and hybrids co-exist

Question 22

what is evolutionary stasis

Answer 22

Long periods of slow / no phenotypic evolution is referred to as evolutionary “stasis”

Can be caused by stabalizing selection

Question 23

can Genetic drift actually change stuff

Answer 23

Genetic drift can generate a substantial amount of evolutionary change.

In some ways there seems to be much less evolution observed than would be expected from genetic drift.

Question 24

what are the 3 key points from BIOL184

Answer 24

1. All organisms ever are connected by a common ancestor.
2. No species is inherently more “advanced”, superior, better, etc than others. The diversity reflects many different ways of adapting and persisting, despite the ever-changing conditions of Earth.
3. All living species are different from their long gone ancestors and by definition the descendants of winners.