Speciation

Question 0

Evolutionary independence

Answer 0

Mutation, speciation, migration and drift operate on populations separately

Question 1

Evolutionary species concept

Answer 1

Independent evolutionary lineage with own evolutionary tendencies and historical fate

Question 2

Biological species concept

Answer 2

A group of actually or potentially interbreeding organisms that are reproductively isolated from all other such groups (interbreeding meaning successfully producing fertile offspring and potentially meaning in a natural setting if not separated by maybe a mountain)

Question 3

Phylogenetic species concept

Answer 3

Smallest monophyletic group of organisms diagnosable by fixed, unique combination of character states (fixed, unique character states can range from single nucleotide substitutions to a major morphological change)

Question 4

Morphospecies concept

Answer 4

Part of phylogenetic species concept, diagnosable by distinct morphological differences, distinct morphological differences in comparable individuals (not stages of lifecycle, not different sexes)

Question 5

Problems with biological species concept

Answer 5

1. How do we know if organisms are potentially interbreeding? - allopatric populations or extinct populations in fossil record
2. Asexual organisms - no interbreeding so can’t group
3. Lateral gene transfer - some distantly related organisms can transfer genetic material (bacteria), is this interbreeding?

Question 6

Allopatric

Answer 6

Geographically isolated

Question 7

Characters to diagnose species under phylogenetic species concept

Answer 7

Unique character states

Question 8

Steps of speciation

Answer 8

1: isolation of populations (required)
2: divergence of populations (required)
3: reinforcement (optional)

Question 9

Sympatric

Answer 9

Something other than geographic isolation

Question 10

Step 1: isolation of populations

Answer 10

Gene flow (migration) disrupted because of allopatric or sympatric speciation

Question 11

Dispersal

Answer 11

Individuals cross barrier, allopatric speciation

Question 12

Vicariance

Answer 12

Barrier divides population, allopatric speciation

Question 13

Sympatric isolation

Answer 13

Polyploidy in plants (increased number of chromosomes, 4n), ecological isolation (different micro habitats, food or hosts, different timing of reproduction)

Question 14

Step 2: divergence of populations

Answer 14

Two isolated populations diverge genetically through:

1. Genetic drift - founder effect and gradual drift fixing different alleles/traits in the two populations
2. Natural selection - experience through different environments and selection pressures
3. Sexual selection - evolve different traits to maximize mating success

Question 15

Step 3: reinforcement

Answer 15

Diverging populations come back into secondary contact (return to sympatric or are no longer isolated), because of divergence when they interbreed hybrid offspring have reduced fitness (better to reproduce with own type - trait to distinguish) selection favors mechanisms to prevent hybridization = prezygotic isolation mechanisms (assortative mating or other mechanisms that prevent fertilization, stop hybridization and increase rate of speciation)

Question 16

Hybridization

Answer 16

Two different species or relatively different populations of the same species mate and produce offspring that may be infertile

Question 17

Sister species and prezygotic isolation

Answer 17

Prediction: sister species should evolve prezygotic isolation more quickly if they are back in the same location (sympatric) - larger differences between species

Question 18

Ring species

Answer 18

A circular distribution of adjacent populations that interbreed, except where the two ends of the ring come together, species so different they don’t recognize each other as the same species so don’t interbreed but are technically same species