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Ch 24: The Origin of Species

2 ways to get new species

Some species concepts

1. biological

2. morphological

3. paleontological

4. ecological

5. phylogenetic

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2

Reproductive isolating mechanisms

boobies

garter snakes E. spotted skunk

W. spotted skunk (late summer)

(late winter)

trampsnails

Reproductive isolating mechanisms

Ensatina eschsholtzi subspecies

mule

male

female

{hinny (opp. parents)}

Red & purple sea urchins

rice strains

Hybrid zone

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Formation of a hybrid zone

Breakdown of reproductive barriers

eg: Lake Victoria cichlids

Modes of speciation

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4

Galapagos finches

SBM Fig. 19.17!Crested honeycreeper!Sips flower nectar!

Poo-uli!

Feeds on snails and!invertebrates!

Black mamo!

Extinct!Sipped flower nectar!

Akialoa!

Picks food from!cracks in the bark!

Akiapolaau!

Chisels holes in bark!to get insects!

Maui parrot bill!

Rips away bark to!find insects!

‘I��’iwi!Sips flower nectar!

Maui creeper!

Forages among!leaves and branches!

Ula-ai-hawane!

Extinct!Habits unknown!

Maui!

Hawaii!

Apapane!Sips flower nectar!

Kauai!

Oahu!

Hawaiian honey-creepers

Silverswords & relatives

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Grand Canyon antelope squirrels

Parapatric speciation: Habitats are linked but separated by variation in mating

eg: “ring species” Ensatina salamanders

Modes of speciation

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Polyploidy:

autopolyploidy - formed by chromosome doubling

The major species grown worldwide is Solanum tuberosum (a tetraploid with 48 chromosomes), and modern varieties of this species are the most widely cultivated. !

There are also four diploid species (with 24 chromosomes): S. stenotomum, S. phureja, S. goniocalyx, and S. ajanhuiri. !

Plains/red viscacha rat

4n = 102

(Mountain) Viscacha rat

2n = 56

Rare mammal example

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Polyploidy:

allopolyploidy: hybridization followed by chromosome duplication

Primula!floribunda!

Primula!kewensis!

Primula!verticillata!

Kew Garden hybrid primrose

(sterile polyploid appeared in late 1890s, fertile allopolyploid obtained ~1905)

hybrid

From Himalayas From Africa

or Arabia

allopolyploid allopolyploid

Allopolyploids in Tragopogon (goatsbeard/salsify) - recent speciation

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Lake Victoria cichlids

Hawthorne maggot fly range!

Apple maggot fly and Hawthorn maggot fly range!

Rhagoletis

Sympatric speciation by habitat selection

What is the rate of evolutionary change?

Darwin & others

Eldredge & Gould (1972)

Genetics of speciation

Single gene speciation: Japanese land snail (Euhadara)

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Changing genes influence pollinator choice

bumble-bees prefer

humming-birds prefer

more visits by hummingbirds

more visits by bumblebees

Drosophila pseudoobscura 2 subspecies can’t interbreed (at least 4 loci involved)

Large numbers of genes involved

How long does speciation take?

- seems to be considerable variation

- once started can be rapid

How often does it happen?

- as much as to produce all species on Earth (both extant & extinct)

How do larger level changes (Macroevolution) occur?

built on species-level changes?

special circumstances?