Speciation And Extinction

Front 1

Speciation: definition

Back 1

the process of genetic change between parent and daughter populations

Front 2

Genetic isolation

Back 2

§ When is genetic isolation sufficient to designate a new species

Asexually reproducing species must be classified

Front 3

○ Mutations

Back 3

§ Involves genetic change in individuals
§ Random events
□ However, often associated with non-random events like radioactivity
® Probability of persisting through a population is small
§ Generally maladaptive

Front 4

Mechanisms of genetic differentiation (5)

Back 4

Genetic drift,Genetic fixation, island biotas, natural selection

Front 5

Genetic drift

Back 5

§ The change in the gene frequency of a population solely by chance
□ One of the two fundamental processes associated with speciation
□ Occurs in small populations--not likely to occur in large populations
□ Shift in terms of the traits that one might see,

Results in the elimination of certain genes from the gene pool

Front 6

○ Island biotas

Back 6

§ Genetic drift on oceanic islands
§ Founders principle
□ Traits of a new population can be traced to a few ancestral individuals

Ancestral individuals lacked the full range of characteristics of the source population

Front 7

Natural selection

Back 7

§ Population
□ Sum of individuals of a similar species
§ Deme *

Subpopulation where there is an equal probability of all possible mating combinations
§ Divergence of a species in response to a variable environment
§ Phenotypic traits are selected fro (or against) based on their adaptive advantage
§ Natural selection acts on individuals and population by changes the characteristics over time

Front 8

Observable facts of natural selecion.

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1) Parents produce more offspring than can survive
2) There is phenotypic variability exists within populations
3) Some type of inheritance involved

Front 9

Geography of Speciation

Back 9

Allopatric
Sympatric
parapatric
Quasi sympatric (nesting)

Front 10

Allopatric speciation

Back 10

§ Most important from a geographic perspective
§ Speciation in geographic isolation
§ Decreases gene flow
§ Vicariance
□ Where there is no return from colonized location to mothership (there is no interchange between locations)

Front 11

Sympatric speciation

Back 11

§ This is the speciation with overlapping geographic range between parent and daughter species
§ Observed in tropical settings
§ Competitive interaction
§ Relates to realized and fundamental niche
§ Climate can influence how members of species interact with each other
§ If there is an additional chromosome in the gene pool, there is a greater chance for diversification

Daughter species of polyploid species will be larger, more vigorous, and more productive

Front 12

Parapatric speciation

Back 12

Speciation in adjacent geographic ranges

Front 13

Quasi sympatric speciation (nesting)

Back 13

§ A type of sympatric speciation
§ Overlapping ranges of two or more demes

Front 14

Species Selection…Why do some species persist over longer period of time than other species?

Back 14

○ Successful organisms share two traits:
§ PERSISTENCE DURING PERIODS OF UNFAVORABLE CONDITIONS
§ Opportunistic during periods of favorable conditions

Front 15

Speciation Rates (2)

Back 15

Phyletic gradualism
punctuated equilibrium

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Phyletic gradualism

Back 16

one way of looking at speciation rates
□ This is how Darwin looked at it even though he knew that it wasn't the whole truth
□ Consistent rate of evolution resulting from natural selection and allopatric speciation
® Common among organisms with limited dispersal capacities
® Small phenotypic changes

Front 17

Punctuated equilibrium model

Back 17

□ Rapid changes over short period of time with prolonged periods of little change
® Common among organisms that have rapid gene flow through large populations

Front 18

Endemics

Back 18

restricted to a particular area
Refer to any taxonomic level but usually species level

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• Relicts (two types)

Back 19

Taxonomic and Biogeographic

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Taxonomic relicts

Back 20

sole survivors of a diverse taxonomic group
§ Eg: dinosaurs/birds

Front 21

Biogeographic relicts

Back 21

narrowly endemic descendants of once widespread taxa
§ Eg: sequuoia

Front 22

Provincialism

Back 22

coincidental occurrence of endemic forms at a regional scale
○ Relates to:
§ Biogeographic regions consider the major geographic regions as home-bases of certain biota
○ Quantifying biogeographic regions
§ SIMILARITY INDICES
□ Sorensons's and Simpson's index compares combined species with all of the species in other areas

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Cosmopolitan

Back 23

global distribution
○ GENERALLY RESTRICTED TO HIGHER TAXON LEVELS
○ Less than 1% of families are cosmopolitan
○ Disjunctions: isolated populations of a taxonomic group
§ Long-distance dispersal

Extinction in intervening areas

Front 24

Dispersal

Back 24

○ Important because of its influence on gene flow, competition, and geographic range
○ Idea of transferring organism from one location to another location
○ Emigration of "offspring" away from the parent population
§ Offspring: disseminates and propagates
□ Seeds sprouts, spores, bulbs in plants

Mating pairs or gravid females in animals

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Why disperse?

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§ Decrease competition within species
§ Mode of survival: early colonizing species
□ Special adaptations
® Tolerant of stressed environments
® High capacity of dispersal
® High genetic plasticity
® Poor competitors

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Dispersal's role in evolution

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decreased gene flow

Front 27

Waif biota: island environments

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○ WEEDY SPECIES
○ Genetic drift and founders effect
○ Poor competitors

High probability of extinction when there is an introduction of exotic species

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Modes of dispersal (3)

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Secular migration,
Diffusion, Long-distance jump dispersal

Front 29

Secular migration

Back 29

§ Movement of entire populations over long periods
§ Zonal
§ Appreciable evolutionary change

Associated with climate chang

Front 30

Phyletic gradualism

Back 30

one way of looking at speciation rates
□ This is how Darwin looked at it even though he knew that it wasn't the whole truth
□ Consistent rate of evolution resulting from natural selection and allopatric speciation
® Common among organisms with limited dispersal capacities
® Small phenotypic changes

Front 31

Punctuated equilibrium model

Back 31

□ Rapid changes over short period of time with prolonged periods of little change
® Common among organisms that have rapid gene flow through large populations

Front 32

Endemics

Back 32

restricted to a particular area
Refer to any taxonomic level but usually species level

Front 33

• Relicts (two types)

Back 33

Taxonomic and Biogeographic

Front 34

Taxonomic relicts

Back 34

sole survivors of a diverse taxonomic group
§ Eg: dinosaurs/birds

Front 35

diffusion

Back 35

§ Gradual (several generations)
§ Population gradient ( density) moves from higher to lower

Resource competition drives the process

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○ Long-distance jump dispersal

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§ Most rapid
§ One generation
§ Crosses barriers

Waif biotas

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Barriers

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○ Any abiotic or biotic factor that inhibits gene flow between populations
§ Consider type of barrier
§ And also consider age of barrier
§ History of barrier

Taxonomic differentiation will provide feel for age of barrier

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Corridor

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Narrow continuation of habitat between two areas
not large enough for organism to become estabilshed within corridor

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Filter

Back 39

limits migration to organisms having high adaptive tolerance
often discontinuous habitat
smaller habitats

Front 40

Landscape ecology

Back 40

looks at ecosystems
creation of fragmented landscape barriors islands corridors and filters
observes a variety of spatial attributes of features