Evolutionary biology 6

Question 1

Contributors to speciation

Answer 1

• Chance
• Ecology
• Reinforcement
• Sexual selection

Question 2

(ch) mutation order speciation

Answer 2

different population finds different genetic solutions to the same problem

Question 3

(ch) what can lead to dobzhansky-muller incompatibilities

Answer 3

long term genetic drift (v slow)

Question 4

(ch) founder effect speciation

Answer 4

when a small satellite population diverges from a large ancestral population (peripatric speciation). genome of the population will depend entirely on few founding memebers.

e.g. Paradise kingfishers - each island in new guinea has their own species of which is morphologically different.

Question 5

(ch) polypoid speciation

Answer 5

• really important in plant speciation
• saltational origin of new species
• usually formed by a failure of division in meiosis

e.g. plains viscacha rat - only polyploid mammal

Question 6

Saltational speciation

Answer 6

a sudden and large mutational change from one generation to the next, potentially causing single-step speciation.

Question 7

Peripatric speciation

Answer 7

a mode of speciation in which a new species is formed from an isolated peripheral population.

Question 8

Advantages of polyploid speciation

Answer 8

• heterozygote advantage
• extreme phenotypic traits
• reproductive isolation
• duplication on a big scale

Question 9

advantages of homoploid speciation

Answer 9

have much higher genetic variation than polyploids

Question 10

homoploid speciation

Answer 10

A form of hybrid speciation that is relatively common in plants, occurs when an infertile hybrid becomes fertile after doubling of the chromosome number. Hybridization without change in chromosome number is called homoploid hybrid speciation.

Question 11

(ec) enviromental differences leading to speciation

Answer 11

• habitat structure
• climate
• resources

Question 12

(ec) Ecological interactions leading to speciation

Answer 12

• Diesease
• competition
• behavioural interference
• normally occur in sympatry
• can cause ecological character displacement

Question 13

(ec) Example of speciation due to ecology

Answer 13

E.g. Timema cristinae (stick insect) - 2 different ecomorphs that occur on 2 different host plants.

*Habitat isolation - both morphs stay on host plant
*Immigrant inviability - ecomorph on wrong plant
more susceptible to predation
*sexual isolation - do not mate with each other
*cryptic isolation - after hybrid mating females overall lifetime is reduced

Question 14

(ec) Second example of speciation due to ecology

Answer 14

E.g. Howea palm - thatch and curly palm, entire genome is the same but 4 loci

• live closely together (would expect interbreeding)
• only 6 hyrbids ever found, each species has a: soil preference and differing flowering times. causes huge prezygotic barrier.

good example of sympatric speciation.

Question 15

(ec) Ecological character displacement

Answer 15

E.g. interspecific competition - between brook and ninespine sticklebacks

• when ninespine sticklebacks present brooks show characteristics of benthic living rather then pelagic.
• stronger jaws and wider bodies to survive benthic habitat

benthic - bottom layer
pelagic- “middle”

Question 16

(Re) cascade reinforcement

Answer 16

1. Selection is favouring prezygotic mechanisms which keeps populations from breeding together (reduced gene flow)
2. Species 1+2 now have areas where different mating mechanisms are favoured, which can lead to isolation within the species.

E.g. Spadefoot Toads

Question 17

How are reinforcement and gene flow linked

Answer 17

• Reinforcement acts to prevent gene flow
• but reinforcement needs gene flow initially
• but not too much

Question 18

allopolyploid

Answer 18

occurs when the individual has more than two copies but these copies, come from different species.

Question 19

autopolyploid

Answer 19

when an individual has more than two sets of chromosomes, both of which from the same parental species.