Speciation

Question 1

What are four species concepts?

Answer 1

• Linnaean: focus on morphological differences, can be applied to asexual, sexual and fossilized species
• Biological: focus on populations’ ability to reproduce with each other; populations that are reproductively isolated are separate species
• Phylogenetic: relatedness and evolution traced back through rise in synapomorphies
• Lineage: species consist of smaller metapopulations that can share some degree of hybridization

Question 2

Define allopatric and sympatric speciation

Answer 2

allopatric = geographical isolation/changes separates the gene pool of a population to form 2+ species

sympatric = separation of a population’s gene pool without geographic barriers, due to development of new niches, behavioural changes etc.

Question 3

What type of speciation was involved with squirrels at the Grand Canyon?

Answer 3

allopatric (canyon divided population)

Question 4

What type of speciation was involved with elk and red deer?

Answer 4

allopatric (continential drift)

Question 5

What are some examples of prezygotic barriers?

Answer 5

• spawning asynchrony
• mismatched sexual structures
• behavioural isolation (rituals, chemical cues)
• ecological isolation

Question 6

What are some examples of postzygotic barriers?

Answer 6

• gametic incompatibility
• hybrid inviability (hybrid does not survive)
• hybrid sterility (hybrid cannot reproduce)

Question 7

What is hybrid speciation?

Answer 7

When hybridization is discouraged between species because the hybrids are unable to compete successfully against their parent species (unsuitable niches)

Question 8

How can cryptic species (species that look nearly identical) prevent hybridization?

Answer 8

species recognition via songs

Question 9

What occured in the Isthmus of Panama?

Answer 9

before barrier
- shrimp from Pacific and Caribbean interbred

after barrier
- allopatric isolation led to speciation of separate shrimp species

Question 10

What is parapatric isolation?

Answer 10

subspecies only interact at overlapping edges of ranges (limited overlap for hybridization)

Question 11

What factors played into the rapid speciation of cichlids in Lake Victoria?

Answer 11

• development of pharyngeal jaws/teeth
• colour morphs (led to behavioural changes in sexual selection)

Question 12

What type of hybridization occurred between brown bears and polar bears during the Pleistocene?

Answer 12

introgressive (gradual exchanges of genes)

Question 13

Describe the theory on how polar bears derived from brown bears

Answer 13

1) a small portion of a northern brown bear population moved north during a warm glacial period
2) during a cold glacial period selection on the population increased and favoured alleles on APOB gene that benefitted lipid rich diet (seals)
3) mutation on fur colour favoured lighter individuals and made them more fit

Question 14

What is allopolyploidy?

Answer 14

multiple chromosomes on a single gene all derived from different species via hybridization (most common in plants)