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5/6/15
1
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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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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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?