Speciation - Macroevolution

What is a Species?

What is a Species?

• Morphological species• Problems?

Variable Morphology

Grown in water Grown on land

Figure 14.3a

What is a Species?

• Biological Species Concept– Population– Interbreed– Fertile offspring– Reproductive isolation

Reproductive Isolation

Isolating Mechanisms

• Prezygotic isolation

• Postzygotic isolation

Figure 14.4

Prezygotic IsolationBehavioral Isolation

Prezygotic Isolation

Temporal Isolation

Prezygotic Isolation

Ecological Isolation

Prezygotic Isolation

Mechanical Isolation

Prezygotic Isolation

Gametic Mortality

Postzygotic Mechanisms

• Hybrid inviability

• Hybrid sterility

• Hybrid breakdown

Figure 14.3D

Mechanisms of Speciation

• Allopatric speciation

– Barrier prevents gene flow

• Sympatric speciation

– W/in home range

Figure 14.7

Allopatric Speciation

A. harrisi A. leucurus

Figure 14.4

– Isolation in Death Valley• New species of pupfish

Figure 14.5B A pupfish

Allopatric Speciation

Figure 14.9

Sympatric Speciation • Polyploidy

• Change in chromosome number (3n, 4n, etc.)

Parent species

Meioticerror

Self-fertilization

Offspring may be viable and self-fertile

Zygote

Unreduced diploid gametes

2n = 6Diploid

4n = 12Tetraploid

O. gigas

O. lamarckiana

AA BB

AB

AA BB DD

ABD

AA BB DD

Triticum monococcum(14 chromosomes)

Wild Triticum(14 chromosomes)Sterile hybrid

(14 chromosomes)

Meiotic error andself-fertilization

T.turgidumEmmer wheat(28 chromosomes)

T.tauschii(wild)(14 chromosomes)

Sterile hybrid(21 chromosomes)

Meiotic error andself-fertilization

T.aestivumBread wheat(42 chromosomes)

Possible Evolution of Wheat

Figure 14.7B

Models for Speciation

• Gradual change model– Small changes over time

• Punctuation model– Brief period near divergence

Figure 14.12

How have complex structures evolved?

•Many stages• From simpler versions w/ the same basic

function

Figure 14.11

Light-sensitivecells

Light-sensitivecells

Fluid-filled cavity Transparent protectivetissue (cornea)

Cornea

Layer of light-sensitivecells (retina)

Nervefibers

Nervefibers

Opticnerve

Opticnerve

Opticnerve

Eyecup Retina

Lens

Patch of light-sensitive cells Eyecup

Simple pinholecamera-type eye

Eye withprimitive lens

Complexcamera-type eye

Limpet Abalone Nautilus Marine snail Squid

• Changes in development

• Timing and rate of growth

How?

Figure 14.12A

Figure 14.12B

Chimpanzee fetus Chimpanzee adult

Human fetus Human adult

Stephen Jay Gould (evolutionary biologist)

Mickey Mouse “evolved”

Copyright DisneyEnterprises, Inc.

Mickey?

• Evolutionary trends do not mean that evolution is goal directed

Figure 14.13

Hippidion and other genera

Nannippus

NeohipparionHipparion

Sinohippus Megahippus

Archaeohippus

Callippus

HypohippusAnchitherium

Miohippus

Parahippus

Paleotherium

Propalaeotherium

Pachynolophus Orohippus

Epihippus

Equus

Pliohippus

Merychippus

Mesohippus

HyracotheriumGrazersBrowsers

EO

CE

NE

OL

IGO

CE

NE

MIO

CE

NE

PL

IOC

EN

EE

R

EC

EN

TP

LE

IST

OC

EN

End Goal? No!

• Rocks and fossils – Radiometric dating

• radioactive isotopes

Geologic Record

Figure 14.17

Figure 14.16

Table 15.1

• Impact on macroevolution?

Edge of one plate being pushed over edge ofneighboring plate (zones of violent geologic events)

Antarctic Plate

AustralianPlate

Splitdeveloping

IndianPlate

Eurasian PlateNorth

AmericanPlate

SouthAmerican

Plate

NazcaPlate

PacificPlate

ArabianPlate

AfricanPlate

Figure 15.3A

Continental drift

Figure 15.3B

0

65

135

245

Mill

ions

of

years

ago

Pale

ozo

icM

esozo

icC

en

ozo

ic

North AmericaEurasia

Africa

South America

India

AntarcticaAustralia

Laurasia

Gondwana

Pang

aea

Continental drift

• Volcanoes and earthquakes

San Andreas Fault

NorthAmericanPlate

San FranciscoSanta Cruz

Los Angeles

PacificPlate

California

Figure 15.4A, B

Figure 14.18

• Permian and Cretaceous periods– Dinosaurs?

Mass extinctions

Adaptive Radiation

• Burst of divergence • Single lineage gives rise to

many new species• New species fill vacant

adaptive zone

Hawaiian Islands

Adaptive radiations:– Honeycreepers

– Fruit flies (Drosophila) - 40% of fruit fly species are found in Hawaii

Hawaiian Honeycreepers

FOUNDER SPECIESFigure 18.7Page 297

Classifying Diversity

• Taxonomy• Phylogeny

– Homologous structures and molecular sequences

– Evidence of common ancestry

Figure 15.6

Ancestry? OrConvergent evolution?

PHYLOGENY

• Systematics– Connects

classification w/ evolution

• Binomial – Genus – Species

Phylogeny Species

Genus

Family

Order

Class

Phylum

Kingdom

Domain

Feliscatus

Felis

Felidae

Carnivora

Mammalia

Chordata

Animalia

Eukarya

Species

Feliscatus

(domesticcat)

Mephitismephitis

(striped skunk)

Lutralutra

(Europeanotter)

Canisfamiliaris

(domestic dog)

Canislupus(wolf)

Genus

Family

Order

Felis

Felidae

Carnivora

Mustelidae

Mephitis Lutra Canis

Canidae

Figure 15.7B

• Phylogenetic treePHYLOGENY

Figure 14.24

– The simplest (most parsimonious) hypothesis

Figure 15.8B

Lizards Snakes Crocodiles Birds

Common reptilian ancestor

CLADOGRAMS