L7: Speciation

Question 1

Evolution happens on large and small scales

What is Macroevolution?

Answer 1

Refers to large scale changes that occur over extended time periods, such as the formation of new species and groups.

Question 2

Evolution happens on large and small scales

What is Microevolution?

Answer 2

Refers to small scale changes that affect just of or a few genes and happen in populations over shorter timescales.

Question 3

What are the 4 mechanisms of genetic differentiation?

Answer 3

1) Mutation: changes in DNA
2) Genetic drift: changes in gene frequency within a population caused by chance. Non-influence of natural selection
3) Natural selection: change in a population that occurs because individuals express genetic traits that alter their interaction with their environment so as to enhance their survival and reproduction.
4) Gene flow: impede genetic divergence

Question 4

Define speciation

Answer 4

The process in which two or more contemporaneous species evolve from a single ancestral population (Lomolino et al, 2010)

Question 5

How can the disruption of a gene flow result in speciation?

Answer 5

In a population of organisms, gene flow maintains an interbreeding group.

Disruption of gene flow, physically or through a behaviour change, can isolate a population.

Population becomes so distinct that it becomes reproductively isolated. Even if populations are rejoined, individuals no longer interbreed.

Question 6

What is allopatric (or geographically isolated) speciation?

Answer 6

Formation of new species that occurs when populations are geographical separated (Lomolino et al, 2010)

Question 7

There are two modes of allopatric speciation:

Answer 7

1) Vicariance

2) Founder events

Question 8

What is vicariance allopatric speciation?

Answer 8

Environmental change can create a barrier to dispersal within a species range. Such events are called vicariant events.

Question 9

What are founder events?

Answer 9

Individuals may disperse across an existing barrier to colonize a previously uninhabited region (Mayr 1954).

Question 10

Ways to separate populations?

Answer 10

Long-distance dispersal events

Vicariance events e.g., flooding of a land bridge, separation of continents, habitat change, emplacement of an isthmus, growth of an ice sheet.

Question 11

Allopatric speciation mode I: Vicariance

Answer 11

Ancestral distribution range of species.

Populations diverged over time and eventually will be recognized as separate species.

Barrier subdivided species. The isolated populations diverge in geographic isolation to form new species.

Question 12

Allopatric speciation mode II: founder events?

Answer 12

Individuals may disperse across an existing barrier. In oceanic islands and isolated patches.

Other important concepts

Population bottleneck
Genetic drift
Often seen on islands

Question 13

What is speciation without physical separation?

Answer 13

Sympatric Speciation

Question 14

What is sympatric speciation?

Answer 14

Differentiation of two isolated species from one initial population within the same local area.
Gene flow potentially could occur!
Factors such as: chromosomal changes (common in plants “polyploidy”) and non-random mating (in animals) alter gene flow.

Question 15

Pollination of most species is by…

Answer 15

Resin collecting bees

Question 16

What is the mechanism of sympatric speciation?

Answer 16

When a population uses resources that are different from the original population.

Question 17

What is the sympatric speciation that goes on in plants?

Answer 17

Polyploidy- Sympatric speciation (also parapatric) can also occur though chromosomal change!

Question 18

What is polyploidy sympatric speciation?

Answer 18

During meiosis (gamete formation) chromosomes do not segregate normally but double up in various combinations, often fatal but sometimes viable.

After the change, only that group of polyploids successfully interbreeds.

Common in plants, because many plants self-pollinate.

Question 19

Sympatric speciation: sometimes is difficult to demonstrate

Answer 19

1) Current overlap between 2 species does not necessary mean that their ranges overlapped at the time of speciation.
2) Which scale? Sympatric at regional scale but perhaps not at local scale? Researchers needs to determine that home ranges of breeding members of the ancestral population did indeed overlap.
3) Closely related species that have not had the time to experience appreciable range shifts.

Question 20

What is parapatric speciation?

Answer 20

Parapatric speciation is a mode of speciation in which differentiation occurs when two populations have contiguous but narrowly overlapping ranges, often representing two distinct habitats. An intermediate between allopatric and sympatric