IMPORTANT for -ESA

How would you go about discerning whether these two are representatives of ONE SPECIES OR TWO SPECIES?

http://www.fws.gov/redwolf/aboutredwolf.html

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

EX. Shrimp Isthmus of Panama…p424

Two kinds of Allopatric (your text does not distinguish between these)

1. Vicariance events-Pop. is split into two or more parts

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

Now what is happening here?So is this a

good visual to represent allopatric speciation?

Sympatric SpeciationWithin the geographic range of parent species-gene 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 larvae-Apples 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 both-

Is 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!)