I. WHAT IS A SPECIES?

A. EMPHASIZE PROCESS

1. BIOLOGICAL SPECIES CONCEPT

2. RECOGNITION SPECIES CONCEPT

B. EMPHASIZES PATTERNS

1. PHYLOGENETIC SPECIES CONCEPT

SPECIATION:

1. HOW DOES ONE GENE POOL SPLIT INTO TWO?

2. WHAT MAINTAINS SEPARATE GENE POOLS?

II. REPRODUCTIVE ISOLATING MECHANSIMS

A. EXTRINSIC BARRIERS

1. GEOGRAPHIC

2. ECOLOGICAL

II. REPRODUCTIVE ISOLATING MECHANSIMS

A. EXTRINSIC BARRIERS

B. INTRINSIC BARRIERS

1. PREZYGOTIC

-PREMATING

-LOCK AND KEY

-GAMETIC INCOMPATIBILITY

2. POSTZYGOTIC

-ZYGOTE INVIABILITY

-HYBRID DISADVANTAGE

-HYBRID DEATH OR STERILITY

Is reproductive isolation a direct or by-product of evolution?

IV. GEOGRAPHY OF SPECIATION

A. ALLOPATRY

B. SYMPATRY

C. PARAPATRY

A B

AB

A B

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

-GEOGRAPHICALLY ISOLATED POPULATIONS DIVERGE IN RESPONSE TO NOVEL ENVIRONMENT OR NEW SELECTIVE PRESSURES

-ADAPTATION TO NEW ENVIRONMENT RESULTS IN REPRODUCTIVE ISOLATION

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

• POPULATIONS (OR SPECIES) DIVERGE IN RESPONSE TO FOOD RESOURCES

• CHANGE IN BILL AND HEAD MORPHOLOGY

PREDICTION: CHANGES IN MORPHOLOGY RESULTS IN REPRODUCTIVE ISOLATION

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

• ARE DIFFERENCES IN HEAD MORPHOLOGY USED FOR CONSPECIFIC RECOGNITION?

SUBJECT MODEL NO. APPROACH NO. PECKS

G. scandens

2.8 ± 0.4

2.0 ± 0.4 1.6 ± 0.9

7.9 ± 4.7

different

Ratcliffe and Grant 1983

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

• ARE DIFFERENCES IN HEAD MORPHOLOGY USED FOR CONSPECIFIC RECOGNITION?

SUBJECT HEAD MODEL NO. APPROACH NO. PECKS

G. scandens

3.6 ± 0.8

2.0 ± 0.4 2.5 ± 0.8

5.4 ± 1.9

G. scandens BODY

G. scandens BODY

different

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

• ARE DIFFERENCES IN HEAD MORPHOLOGY USED FOR CONSPECIFIC RECOGNITION?

SUBJECT HEAD MODEL NO. APPROACH NO. PECKS

G. scandens

2.5 ± 0.6

2.9 ± 1.1 2.1 ± 1.9

0.6 ± 0.4

G. fortis BODY

G. scandens BODY

not different

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

• ARE DIFFERENCES IN HEAD MORPHOLOGY USED FOR CONSPECIFIC RECOGNITION?

SUBJECT HEAD MODEL NO. APPROACH NO. PECKS

G. scandens

2.6 ± 0.6

1.6 ± 0.2 3.1 ± 1.6

2.7 ± 1.3

G. fortis BODY

G. scandens BODY

not different

STUDY SUGGESTS THAT BOTH HEAD AND BODY SIZE ARE IMPORTANT

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

DO CHANGES IN HEAD MORPHOLOGY INFLUENCE OTHER TRAITS?

Podos et al. 2004

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

CHANGES IN HEAD MORPHOLOGY INFLUENCE SONG PRODUCTION

Podos 2001

intraspecific variation: G. fortis

interspecific variation

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

SONG IMPORTANT IN CONSPECIFIC RECOGNITION

SONG TYPE

G. fortis

G. scandens

NUMBER OF NEIGHBORS ATTRACTED

23

0

4

25

Ratcliffe and Grant 1983

V. MODELS OF SPECIATION

1. ALLOPATRY

A. DIVERGENT NATURAL SELECTION

OTHER STUDIES SHOWING NS AND SPECIATION

Three-spined stickleback feeding

Pea Aphids host plant

Walking sticks host plant

Heliconius butterflies warning coloration

V. MODELS OF SPECIATION

1. ALLOPATRY

B. DIVERGENT SEXUAL SELECTION

-DIFFERENCES IN MATE CHOICE PROCESS RESULTS IN DIFFERENCES IN SIGNALS USED IN COMMUNICATION

-CHANGES IN SIGNALS RESULTS IN REPRODUCTIVE ISOLATION (PREMATING)

PREDICTIONS: DIVERGENCE ONLY IN SECONDARY SEXUAL CHARACTERS

PREDICTIONS: DIVERGENT CHARACTERS USED IN CONSPECIFIC RECOGNITION

Gryllus spp. crickets by Gray and Cade (2000)

PREDICTION 1: “SPECIES” SHOULD ONLY DIFFER IN SECONDARY SEXUAL CHARACTERS

-CRYPTIC SPECIES: INDISTINGUISHABLE MORPHOLOGICALLY

-ONLY DIFFER IN MALE SEX TRAIT: CALL RATE

Gryllus rubens

Gryllus texensis

V. MODELS OF SPECIATION

1. ALLOPATRY

B. DIVERGENT SEXUAL SELECTION

PREDICTION 1: “SPECIES” SHOULD ONLY DIFFER IN SECONDARY SEXUAL CHARACTERS

-CRYPTIC SPECIES: INDISTINGUISHABLE MORPHOLOGICALLY

-ONLY DIFFER IN MALE SEX TRAIT: CALL RATE

Gryllus spp. crickets by Gray and Cade (2000)

V. MODELS OF SPECIATION

1. ALLOPATRY

B. DIVERGENT SEXUAL SELECTION

PREDICTION 2: FEMALES SHOULD USE DIVERGENT TRAITS IN RECOGNIZING CONSPECIFICS

Gryllus spp. crickets by Gray and Cade (2000)

V. MODELS OF SPECIATION

1. ALLOPATRY

B. DIVERGENT SEXUAL SELECTION

OTHER STUDIES

TAXA TRAIT

HAWAIIAN CRICKETS SONG

BOWERBIRDS BOWER STRUCTURE

JUMPING SPIDERS MALE COLORATION

HAWAIIAN Drosophila HEAD SIZE (COURTSHIP)

V. MODELS OF SPECIATION

1. ALLOPATRY

B. DIVERGENT SEXUAL SELECTION

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

PREDICTIONS: POPULATIONS DIVERGE IN SYMPATRY

PREDICTIONS: POPULATIONS DIVERGE IN RESPONSE TO SPECIFIC ECOLOGICAL FACTORS

PREDICTION: HABITAT SPECIFIC MATING RESULTS IN REPRODUCTIVE ISOLATION

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

-POPULATIONS DIVERGE IN RESPONSE TO SPECIFIC ENVIRONMENTAL FACTORS DESPITE NOT BEING GEOGRAPHICALLY ISOLATED

-PRIME CANDIDATES: INSECT – HOST PLANT

-NEED POLYMORPHISM AND DISRUPTIVE SELECTION

-VERY STRICT MODEL BECAUSE GENE FLOW CAN PREVENT SPECIALIZATION

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

Example(?): apple maggot fly Rhagoletis pomonella

-work by many started by Walsh (late 1800’s) and Bush.

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

Apple maggot fly Rhagoletis pomonella

-MID 1800s, SOME SHIFTED TO DOMESTIC APPLES

-NEW HOST RACES

IS THIS AN EXAMPLE OF SYMPATRIC SPECIATION?

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

Example(?):

Apple maggot fly Rhagoletis pomonella

PREDICTION1: POPULATIONS DIVERGE IN SYMPATRY

YES, RECORDS SHOW SHIFT TO NEW HOST PLANTS AROUND MID 1800

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

Example(?):

Apple maggot fly Rhagoletis pomonella

PREDICTION 2: POPULATIONS DIVERGE IN RESPONSE TO SPECIFIC ECOLOGICAL FACTORS

-SHIFT FROM HAWTHORNE TO APPLE

ADVANTAGE?

RECIPROCAL TRANSPLANTS OF EGGS (Prokopy and colleagues 1988): LARVAL SURVIVORSHIP

APPLE LARVAE = HAWTHORN LARVAE IN HAWTHORN

APPLE LARVAE = HAWTHORN LARVAE IN APPLE (BOTH DID POORLY!)

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

Example(?): Apple maggot fly Rhagoletis pomonella

PREDICTION 2: POPULATIONS DIVERGE IN RESPONSE TO SPECIFIC ECOLOGICAL FACTORS

-SHIFT FROM HAWTHORN TO APPLE

ADVANTAGE?

-ENEMY FREE SPACE

-TIMING OF EMERGENCE FROM THE GROUND

APPLE PEAKS 3 WEEKS EARLIER THAN HAWTHORN

APPLE Rhagoletis LARVAE LEAVE APPLES 16 DAYS BEFORE HAWTHORN

HAVE TO STAY IN DIAPAUSE LONGER OR WILL ECLOSE IN WINTER – SO APPLE FLIES DEVELOP SLOWER THAN HAWTHORN FLIES

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

Example(?): Apple maggot fly Rhagoletis pomonella

PREDICTION 3: HABITAT SPECIFIC MATING RESULTS IN REPRODUCTIVE ISOLATION

- FIELD EXPERIMENTS: MATE AND GROW EXCLUSIVELY IN HOST PLANT

- GENETICS:

SIX LOCI SHOW ASSOCIATION WITH HOST RACE

BUT MANY OTHERS DO NOT

-MARK RECAPTURE

STRONG FIDELITY, BUT 6% MIGRATION

V. MODELS OF SPECIATION

1. ALLOPATRY

2. SYMPATRY

A. DIVERGENT NATURAL SELECTION

OTHER STUDIES:

NONE....

V. MODELS OF SPECIATION

2. SYMPATRY

B. DIVERGENT SEXUAL SELECTION

-DIFFERENCES IN MATE CHOICE PROCESS RESULTS IN DIFFERENCES IN SIGNALS USED IN COMMUNICATION

-CHANGES IN SIGNALS RESULTS IN PREZYGOTIC ISOLATION (PREMATING)

PREDICTIONS: POPULATIONS DIVERGE IN SYMPATRY

PREDICTIONS: DIVERGENCE ONLY IN SECONDARY SEXUAL CHARACTERS

PREDICTIONS: DIVERGENT CHARACTERS USED IN CONSPECIFIC RECOGNITION

V. MODELS OF SPECIATION

2. SYMPATRY

B. DIVERGENT SEXUAL SELECTION

PREDICTION 1: POPULATIONS DIVERGE IN SYMPATRY

-PHYLOGENY: MONOPHYLETIC GROUP IN A SINGLE LAKE

-LAKE IS RECENT AND SMALL

PREDICTIONS 2: DIVERGE ONLY IN SECONDARY SEXUAL CHARACTERS

-SOME DIVERGENCE IN BODY SIZE

-MOST STRIKING IN COLOR

Lake Victoria cichlid: Haplochromis nyererei by Seehausen and van Alphen 1998

Haplochromis nyererei by Seehausen and van Alphen 1998

PREDICTION 3: FEMALES USE COLOR TO FIND CONSPECIFIC

0

0.1

0.2

0.3

Normal Light

Pre

fere

nce

for

mal

es

V. MODELS OF SPECIATION

2. SYMPATRY

B. DIVERGENT SEXUAL SELECTION

Haplochromis nyererei by Seehausen and van Alphen 1998

PREDICTION 3: FEMALES USE COLOR TO FIND CONSPECIFIC

Mono Light

0

0.1

0.2

0.3

0

0.1

0.2

0.3

Pre

fere

nce

for

mal

es

V. MODELS OF SPECIATION

2. SYMPATRY

B. DIVERGENT SEXUAL SELECTION

V. MODELS OF SPECIATION

2. SYMPATRY

B. DIVERGENT SEXUAL SELECTION

OTHER STUDIES

Lake Malawi Cichlids Coloration

V. MODELS OF SPECIATION

3. REINFORCEMENT

THREE STEPS:

- DIVERGE OR CHANGE IN ALLOPATRY

- ESTABLISH SECONDARY CONTACT

- SELECTION AGAINST HYBRIDIZATION RESULTS IN EXAGGERATION OF SEX TRAITS TO FACILITATE CONSPECIFIC RECOGNITION

PREDICTIONS: SECONDARY SEX TRAITS EXAGGERATED WHEN SYMPATRIC

PREDICTIONS: FEMALES USE DIVERGENT TRAITS TO RECOGNIZE CONSPECIFICS

PREDICTIONS: COST TO HYBRIDIZATION

Ficedula ssp. Collared Flycatcher by Saetre and colleagues

PREDICTION 1: TRAITS MORE DIVERGENT WHEN SYMPATRIC

PIED FLYCATCHER COLLARED FLYCATCHER

allopatric

sympatric

V. MODELS OF SPECIATION

3. REINFORCEMENT

Ficedula ssp. Collared Flycatcher by Saetre and colleagues

PREDICTION 2: PIED FLYCATCHERS SHOULD BE MORE RELATED TO PIED FLYCATCHERS THAN TO COLLARED FLYCATCHERS REGARDLESS OF DISTRIBUTION

V. MODELS OF SPECIATION

3. REINFORCEMENT

Ficedula ssp. Collared Flycatcher by Saetre and colleagues

PREDICTION 3:FEMALES USE DIVERGENT PLUMAGE IN RECOGNIZING CONSPECIFICS

TESTED SYMPATRIC FEMALES

V. MODELS OF SPECIATION

3. REINFORCEMENT

Ficedula ssp. Collared Flycatcher by Saetre and colleagues

PREDICTION 3:FEMALES USE DIVERGENT PLUMAGE IN RECOGNIZING CONSPECIFICS

V. MODELS OF SPECIATION

3. REINFORCEMENT

• Pied Fly Catchers (Ficedula spp.)

-hybrid:75% eggs failed to hatch

-pure pairs: 4.9% failed to hatch

Ficedula ssp. Collared Flycatcher by Saetre and colleagues

PREDICTION 4:COST TO HYBRIDIZATION

V. MODELS OF SPECIATION

3. REINFORCEMENT

OTHER STUDIES?

North American Drosophila species Trait unknown

Generally Rare

4. RING SPECIATION

-POPULATIONS EXPAND RANGE AND BEGIN DIVERGING

-ADJACENT POPULATIONS HAVE GENE FLOW

-END OF “RING” NO GENE FLOW

PREDICTIONS: POPULATIONS EXPAND RANGE IN A RING

PREDICTIONS: GENE FLOW BETWEEN ADJACENT POPULATIONS EXCEPT AT END OF THE RING

4. RING SPECIATION

Phylloscopus warblers by Irwin, Bensch and PricePREDICTIONS: POPULATIONS EXPAND RANGE IN A RING

PHYLOGENETIC ANALYSES: ORIGIN SOUTHERN TIBET, EXPAND TOWARDS RUSSIA – MEET IN SIBERIA

4. RING SPECIATION

Phylloscopus warblers by Irwin, Bensch and Price

PREDICTIONS: GENE FLOW (NO REPRODUCTIVE ISOLATION) BETWEEN ADJACENT POPULATIONS EXCEPT AT END OF THE RING

PLAYBACK EXPERIMENTS INDICATE: MALES RECOGNIZE NEIGHBORING POPULATIONS AS CONSPECIFICS, EXCEPT AT THE END OF THE RING

4. RING SPECIATION

Phylloscopus warblers by Irwin, Bensch and Price

PREDICTIONS: GENE FLOW (NO REPRODUCTIVE ISOLATION) BETWEEN ADJACENT POPULATIONS EXCEPT AT END OF THE RING

4. RING SPECIATION

OTHER STUDIES?

Ensatina newts of California

http://www.pbs.org/wgbh/evolution/library/05/2/image_pop/l_052_05.html

VI. GENETICS OF SPECIATION

A. HALDANE’S RULE: WHEN F1 OFFSPRING OF TWO DIFFERENT RACES OR SPECIES ONE SEX IS ABSENT, RARE OR STERILE IT SHOULD BE THE HETEROGAMETIC SEX.

-SOME ORGANISMS SEX IS GENETICALLY DETERMINED

VIA SEX CHOMOSOMES

VI. GENETICS OF SPECIATION

A. HALDANE’S RULE: WHEN F1 OFFSPRING OF TWO DIFFERENT RACES OR SPECIES ONE SEX IS ABSENT, RATE OR STERILE IT SHOULD BE THE HETEROGAMETIC SEX.

WHY?1. DOMINANCE THEORY

-dominant alleles “cover” recessive alleles

-some sex chromosomesare degenerate (little fxn)

-thus detrimental sex-linked alleles are no covered inheterogametic sex

VI. GENETICS OF SPECIATION

A. HALDANE’S RULE: WHEN F1 OFFSPRING OF TWO DIFFERENT RACES OR SPECIES ONE SEX IS ABSENT, RATE OR STERILE IT SHOULD BE THE HETEROGAMETIC SEX.

WHY?1. DOMINANCE THEORY

2. FASTER MALE EVOLUTION

from Presgraves and Orr 2000

VI. GENETICS OF SPECIATION

B. POLYPLOIDY: INHERITING EXTRA COPIES OF CHROMOSOMES

-COMMON IN PLANTS, LESS COMMON IN ANIMALS

VI. GENETICS OF SPECIATION

B. POLYPLOIDY-IN ANIMALSe.g., salamanders, Ambystoma spp.

Ambystoma jeffersonianum (Southern Range – MD, VA...)

Ambystoma laterale (Northern Range – Canada)

-both species diploid (2n = 28)

28j

28l

14j

14j

14l

14l

14j

14l

14j

14l

14l 14jor

sperm

egg

or28j

14l

14j

28l

gynogenetic species

A. platineum A. tremblayi

other polyploid species:

Poecillid fishes, whiptail lizards