Transcript No Slide Title

How would you go about discerning whether
these two are representatives of ONE SPECIES
OR TWO SPECIES?
http://www.fws.gov/redwolf/aboutredwo
lf.html
IMPORTANT for -ESA
1st we had Biological Species Concept (Mayr)
Do they interbreed and produce fertile offspring?
Advantages?
Problems?
1. Asexual species…
2. Fossils
3. Geographically separated
4. Hybridizers
5. Do we really do this?
Your text uses grizzly and polar bears..
Morphological Species Concept
Do they look the same?
Advantages?
Works well for fossils!
Problems?
How different is different?
Sibling species (what are these?)
Often the first thing you do…until time or $$$ to …..
The short-toed treecreeper (Certhia brachydactyla) (left) differs subtly from the common treecreeper (C.
familiaris) (right) in a number of minor characters, including wing pattern and size of the hind toe.
Behavioural patterns and ecology are quite distinct (from Futuyma 1997)
www.mun.ca/biology/scarr/Fut_15_03_treecreepe...
Phylogenetic Species Concept
Evolutionary Species Concept
How long have these two groups been on separate
evolutionary paths?
Reconstruct evolutionary history of populations
(often but not always infer through molecular
genetic info)
EX. Shiitake Mushrooms (Donohue and Hibbett ‘96)
Ranges from Japan, Thailand, Borneo, New Zealand
and Tasmania
Widely cultivated
Threatened due to….
Used all three
“species concepts”
•All are reproductively compatible so ….
•Morphological measurements clustered in 3 groups
•ribosomal RNA-4 distinct groups
So back to our wolves…
Can interbreed-many Canids do!
Look different-RW is smaller, with
longer ears and legs relative to body size,
color different
Genetically-Compared 48,000 single
nucleotide polymorphisms of red wolf,
wolves from NE, our gray wolf, coyotes
and dogs
was 76-80 percent coyote and 20-24
percent gray wolf…USFWS is a species
Whatever it is … considered extinct in the wild by
1980.
Captured individuals in ‘70s combined these with
zoo populations to start a captive breeding program
with 14 individuals….
Have introduced some back into wild.
Today 220 in captivity but only a small number have
persisted in wild….about 100?
http://www.fws.gov/species/species_accounts/bio_rwol.html
Mexican gray wolf-subspecies
Canis lupus baileyi
Speciation-How do new species form?
Must become separated, isolated or cut off from
other populations…
Genes must stop flowing
Populations must become reproductively isolated
Why factors or forces might drive two populations
to accumulate differences over time once they have
been separated?
Different ways of separating a population…Your
text has fish
Two kinds of Allopatric
(your text does not distinguish between these)
1. Vicariance events-Pop. is split into two or more
parts
EX. Shrimp Isthmus of Panama…p424
EX. Grand Canyon.. Antelope squirrels
Other styles of vicariance events
(rivers and canyons are not the only landscape features
that divide populations…)
•Mountain range uplift (Himalayas are still rising)
•Glaciers moved down through N.A.
2. Founder events
Individuals arrive at new island, isolated valley,
ponds
Galapagos- finches…
What affects the likelihood of
speciation
occurring?
Pops are on different islands-what factors will
influence whether they speciate after that
point….?
Depends on the organism..
Barrier to a small rodent (Rocky Mountains)
would not be a barrier to a bird
Depends on selective pressures in each location…..
Depends on size of population…
Remember small populations are more likely to drift
and therefore change in a given amount of time
Depends on passage of time…
Differences accumulate as time since separation
increases
Drosophila Ex in fig 22.8 Mosquito fish Ex p 423
So is this a
good visual
to represent
allopatric
speciation?
Now what is happening
here?
Sympatric Speciation
Within the geographic range of parent speciesgene flow is theoretically possible..
Plants-Polyploidy
Polyploidy (autopolyploidy and allopolyploid)
De Vries-autopolyploid
primrose
But these gametes have a problem they are “unreduced”….
So now imagine the seed with that 4n=12 zygote inside
falls to the ground and germinates into a new individual
primrose (that is tetraploid).
What is the ploidy number of most of its neighbors in the
primrose patch?
Can it mate (cross pollinate) with them??
Polyploidy is an instant, easy, way to make a new species
in plants..
Oats, cotton, potatoes, tobacco, wheat…..
Wild wheat is normal and diploid (2x) like us…but has
2 each of 7 different chromosomes=14 chromosomes
total
Durum wheat is 4x=tetraploid
Bread wheat is 6x=hexaploid
Spelt wheat is 6x=hexaploid
Sympatric speciation in animals is less clear cut, more
difficult!
Don’t have the easy instant species formation of polyploidy.
But lots of interesting other ways of reproductively isolating
animal populations when they are technically in the same
geographic range
Resource choice….
Apple/Hawthorn maggot flies p 426
Apple/Hawthorn Maggot fly
Native hawthorn maggot flies meet and mate and
lays eggs and caterpillar grows up on hawthorn trees.
As apple trees were planted some individuals shifted
to meet and mate and lay eggs on apple trees
For speciation to occur they have to be
reproductively isolated right? (Are they?)
Can then get selection for fast maturing larvaeApples mature fast-so need to get up and off
apple before it falls to ground.
So in the range of the original “parent” species
you see two populations diverging…based on
choice of where they meet to MATE and lay
eggs….
Text also points out are alleles that increase fitness of
apple eaters that are costly to hawthorn eaters!
Are still not officially different species …
Note that specializing on certain food resources alone
typically does not “split populations”….. (in maggot
flies they MATE and feed on different fruits)
Other fascinating situations where MUST have evolved
in same geographic region (so technically sympatric
speciation) BUT we are not clear about the details
(Mate choice in Cichlids in Lake Victoria fits into this
category and there is more to the story than they share in
the text so skip!)
Another famous example are the 900 species of fig trees
each with their own personal wasp polinator!).
//www.entomology.umn.edu/museum
Imagine two populations have been geographically
separated by glaciers that divided the eastern
population from western and have diverged and
become separate species.
As the glaciers recede what are the possible
outcomes?
Some may be fully reproductively isolated and not
interbreed
Some might interbreed and hybrid individuals
might grow and survive creating a hybrid zone.
Fusion -Over time those populations may totally
fuse, initial hybrids interbreed successfully with
parental populations across generations.
Stability -May simply continue to produce
hybrids (some of whom have some reproductive
issues so don’t do great but do ok…)
OR Reinforcement!
When hybrids are less fit we often see selection in
favor of individuals that prefer to mate with their
own species =reinforcement!
Sunflowers-Can new species form through
hybridization?
3 Species…..1, 2, 3,
We know that 1 and 2 hybridize and that 3
morphologically looks like it has characteristics of
bothIs it a hybrid of 1 and 2?
Forced 1 and 2 to hybridize in greenhouse and
then did a series of backcrosses
Morphologically looked like hybrids!
Gene sequence data showed species 3 had
sequences that were similar to both 1 and 2 and the
arrangement of these sequences even matched
sequence data from wild individuals of species 3.
Hypothesis is that species 3 evolved as a
hybridization event (first well documented
example so is always in text books!)