topic 10 - species and speciation

Question 1

other taxons vs species?

Answer 1

*

* All of these are artificial in nature EXCEPT for species

Question 2

Cladogenesis and anagenesis- importance, define

Answer 2

• Species exist by virtue 
	of 
	• Cladogenesis: the 
	branching or splitting of 
	a lineage, and 
	• Anagenesis: 
	evolutionary change 
	within a lineage, 
	resulting in differences 
between sister lineages

Question 3

early species definitions?

Answer 3

• Early 
		○ Typological 
		e.g., Linnaeus: 
		- A species if members 
	sufficiently conforms 
	to that "type" 
		- Clusters of variations 
	(long vs. short tails) 
	would differentiate 
	the species

Question 4

modern - biological species defintion

Answer 4

○ Biological - Mayr, 1942
§ Biological species concept Species are groups of actually or potentially interbreeding nat-
ural populations that are reproductively isolated from other such groups (Mayr 1942).

Question 5

evolutionary definition

Answer 5

Evolutionary species concept A is a single lineage (an
Of or organisms that maintains an identity separate from Other such
which its fate (Wiley 1978).

Question 6

Phylogenetic defintion

Answer 6

of is distiru•t from Other such Clusters, and within Which there
is a of 1989). (2) A
monophyletic group of common ancestry (de Queiroz and Donoghue

Question 7

genealogical definition

Answer 7

enea oglCa spectes concept pecres are ‘ exc uswe groups o organisms, w ere an
exclusive group is one whose members are all more closely related to one another than to
any organism outside the group (Baum and Shaw 1995).

Question 8

recognition definition

Answer 8

Recognition species concept A species is the most inclusive population of individual
biparental organisms that share a common fertilization system (Paterson 1985).

Question 9

cohesion definition

Answer 9

Cohesion species concept A species is the most inclusive population of individuals
having the potential for phenotypic cohesion through intrinsic cohesion mechanisms
(Templeton 1989).

Question 10

Biological species concept

Answer 10

• “Species are groups of actually or potentially interbreeding natural
populations which are reproductively isolated from other such
groups” (Mayr, 1942)
• Focus:
On reproductive isolation

Question 11

strengths and weakness of biological species concept

Answer 11

• Strength
○ Additional genetic perspective
• Weakness
○ Cannot be applied to asexual organisms or fossils
○ Does not apply in allopatry - species already naturally separated
Natural hybridization and gene flow between species exists

Question 12

• Issues with biological species - within pop variation

Answer 12

• Within-population variation
• e.g., Colour variation in birds
○ About 3.5% of all bird species
○ Possibly evolved under selective pressures
○ linked to detectability as affected by variable light conditions
○ Species with multiple plumage colour forms evolve into new species faster than those with one colour form (Hugall & Stuart-Fox, 2012)
• Does not apply in allopatry - only sympatry and parapatry

Question 13

why is natural hybridization and gene flow an issue with the biological species concept? ex?

Answer 13

• Natural hybridization and gene flow
○ An individual formed by mating between unlike forms, usually genetically differentiated populations or species
§ About 16% of bird- & 10% of butterfly species produce hybrids in the wild
§ Blue whale recorded hybridizing with fin whale
○ If hybrid individuals are less viable or less reproductively successful than non-hybrid individuals, the two species
are considered to be good (distinct) species
•

Question 14

• Borderline cases

?

Answer 14

ex northern orioles
hybridize where ranges overlap
ere considered to be separate species, then one species, and now separate again

Question 15

bad taxonomy ex?

Answer 15

• It’s a political and conservation issue since protection depends or distinct species or at least subspecies status
• Ex tutara in NZ - read on it
n 1990 proposed to be two separate species - possible extinction of 10 of 40 pops - on verge on losing one species
○ In 2010 - suggested to be one species/two subspecies - not a conservation issue
• Species - a modern definition
`

Question 16

Species - a modern definition

Answer 16

Genetically differentiated populations
potentially connected by gene flow and separated by reproductive isolations
• Low enough gene flow & strong enough disruptive selection
Clusters of genotypes with discontinuities/gaps between them

Question 17

reproductive isolation kinds?

Answer 17

Isolating barriers to gene flow
○ Pre-mating
§ Ecological isolation; mate recognition
○ Post-mating pre-zygotic (no zygote formed)
§ Mechanical; behavioral; gametic
○ Post-zygotic
§ Hybrid lack of success; hybrid inviability; hybrid sterility
• Read 220-225 in text!!!! Including examples for exam

Question 18

pre mating barriers?

Answer 18

l. Premating barriers: features that impede transfer of gametes to members of other species
A. Ecological isolation: potential mates do not meet
1. Temporal isolation: species breed at different seasons or times Of day
2. Habitat isolation: species mate and breed in different habitats
3. Immigrants between divergent populations do not survive long enough to interbreed
B. Potential mates meet but do not mate
1. Sexual isolation in animals: individuals prefer mating with members of their own species
2, Pollinator isolation in plants: pollinators do not transfer pollen between species

Question 19

ll. Postmating prezygotic barriers: mating occurs, but zygotes are not formed - kinds

Answer 19

A. Mechanical isolation: reproductive Structures Of the sexes do not fit
B. Copulatory isolation: female is not stimulated by males of the other species
C. Gametic isolation: failure of fertilization

Question 20

Ill. Postzygotic barriers: hybrids are formed but have reduced fitness - kinds

Answer 20

Ill. Postzygotic barriers: hybrids are formed but have reduced fitness
A. Extrinsic: hybrids have low fitness for environmental reasons
1. Ecological inviability: hybrids are poorly adapted to both of the parental habitats
2. Behavioral sterility. hybrids are less successful in obtaining mates
B. Intrinsic: low hybrid fitness is independent of environmental context
1. Hybrid inviability: reduced survival is due to genetic incompatibility
2. Hybrid sterility: reduced production Of viable gamateS

Question 21

ex of prezygotic barriers

Answer 21

habitat isolation - wandering garter snake close to water vs plains garter snake away from water
behavioral isolation - eastern and western medowlark - different ranges
temporal isolation - rainbow trout is a spring breeder, brown trout is a fall breeder

Question 22

post mating pre zygotic examples

Answer 22

mechanical - snails w different spirals - copulary organs too differe
gamete- sea urchins fail to attract other gametes

Question 23

post mating post zygotic examples

Answer 23

reduced hybrid viability - salmanders, fail to develop or reach maturity
reduced hybrid fertility - ex mules are sterile
hybrid breakdown - several species of cotton have reduced viability or fertility