24 Speciation

Question 1

Species

Answer 1

an evolutionary independent population or group of populations; generally distinct from other species in appearance, behaviour, habitat, ecology, genetic characteristics etc.

Question 2

What are the four criteria for identifying species?

Answer 2

(1) biological species concept (2) morphospecies concept (3) ecological species concept (4) phylogenetic species concept

Question 3

Biological species concept

Answer 3

a species as a population or group of populations that are reproductively isolated from other groups (no gene flow occurs between them); members of a species can potentially interbreed in nature to produce viable, fertile offspring but cannot interbreed successfully with members of other species

Question 4

Prezygotic isolation

Answer 4

prevents individuals of different species from mating successfully

Question 5

Postzygotic isolation

Answer 5

the hybrid offspring of matings between members of different species either do not survive or cannot reproduce

Question 6

What are the mechanisms of prezygotic isolation?

Answer 6

temporal, habitat, behavioural, gametic barrier, and mechanical

Question 7

Temporal mechanism

Answer 7

populations are isolated because they breed at different times

Question 8

Habitat mechanism

Answer 8

populations are isolated because they breed in different habitats

Question 9

Behavioural mechanism

Answer 9

populations do not interbreed because their courtship displays differ

Question 10

Gametic barrier

Answer 10

matings fail because eggs and sperm are incompatible

Question 11

Mechanical mechanism

Answer 11

matings fail because male and female reproductive structures are incompatible

Question 12

What are the mechanisms of postzygotic isolation?

Answer 12

hybrid viability and hybrid sterility

Question 13

Hybrid viability

Answer 13

hybrid offspring do not develop normally and die as embryos

Question 14

Hybrid sterility

Answer 14

hybrid offspring mature but are sterile as adults

Question 15

Morphospecies “form species” concept

Answer 15

a species as a population or group of populations that have measurably different anatomical features from other groups

Question 16

Ecological species concept

Answer 16

a species as a set of organisms exploiting a single set of resources, having the same range of environmental tolerances, and facing the same predators and parasites

Question 17

Phylogenetic species concept

Answer 17

a species as the smallest monophyletic group in a phylogenetic tree

Question 18

What are phylogenetic species made up of?

Answer 18

populations that share one or more unique synapomorphies

Question 19

What are the advantages and disadvantages of the biological species concept?

Answer 19

Advantage: reproductive isolation = evolutionary independence; Disadvantages: not applicable to asexual or fossil species, difficult to assess if populations do not overlap geographically

Question 20

What are the advantages and disadvantages of morphospecies concept?

Answer 20

Advantage: widely applicable; Disadvantages: subjective, misidentifies polymorphic species, misses cryptic species

Question 21

What are the advantages and disadvantages of ecological species concept?

Answer 21

Advantage: applicable to sexual species; Disadvantage: different species may have similar ecological roles

Question 22

What are the advantages and disadvantages of phylogenetic species concept?

Answer 22

Advantages: widely applicable, based on testable criteria; Disadvantage: relatively few well-estimated phylogenies currently available

Question 23

Cryptic species

Answer 23

a species that cannot be distinguished from similar species by easily identifiable morphological traits

Question 24

Polymorphic species

Answer 24

a species that has two or more distinct phenotypes in the same interbreeding population at the same time

Question 25

What are the ways geographical isolation can occur?

Answer 25

dispersal and vicariance

Question 26

Vicariance

Answer 26

the physical splitting of a population into smaller, isolated populations by a geographic barrier

Question 27

Dispersal

Answer 27

colonists establish a new population in a novel location

Question 28

Allopatric "different homeland" speciation

Answer 28

speciation that occurs when populations of the same species become geographically isolated, often due to dispersal or vicariance

Question 29

Allopatry

Answer 29

condition in which two or more populations live in different geographic areas

Question 30

Sympatry

Answer 30

condition in which two or more populations live in the same geographic area, or close enough to permit interbreeding

Question 31

Sympatric speciation "together homeland'

Answer 31

divergence of populations living within the same geographic area into different species as the result of their genetic (not physical) isolation

Question 32

What types of events can initiate the process of sympatric speciation?

Answer 32

external events like disruptive selection and internal events like chromosomal mutations

Question 33

Niche

Answer 33

range of resources that a species can use and the range of conditions that it can tolerate i.e. the role that a species plays in its ecosystem

Question 34

Sympatric speciation by disruptive selection

Answer 34

sympatric populations may become reproductively isolated by adapting to different ecological niches

Question 35

Reinforcement of divergence

Answer 35

If hybrid offspring have low fitness, natural selection favors the evolution of traits that prevent interbreeding between the populations

Question 36

Hybrid Zone

Answer 36

a geographic area where interbreeding occurs between two species, sometimes producing fertile hybrid offspring; may move over time or be stable

Question 37

What are the possible outcomes of secondary contact between populations?

Answer 37

fusion of the populations, reinforcement of divergence, hybrid zone formation, extinction of one population, creation of new species

Question 38

Fusion of the populations

Answer 38

the two populations freely interbreed; occurs whenever populations of the same species come into contact

Question 39

Extinction of one population

Answer 39

if one population or species is a better competitor for shared resources, then the poorer competitor may be driven to extinction

Question 40

Creation of new species

Answer 40

if the combination of genes in hybrid offspring allows them to occupy distinct habitats or use novel resources, they may form a new species