Speciation The actual “origin of species” - PowerPoint Presentation

Slide1
Slide2

Speciation

The actual “origin of species”

Reduction in

gene

flow, genetic and phenotypic change in populations

The study of speciation requires that species be realSlide3

Speciation

Speciation is the antidote to sex

Keeps together adaptive groups of traits

New species most often

uniparental

Phylogeny is genealogy of species

Branching treeSlide4

Hybridization

Mules

Fertile interspecific hybrids are common in perennial plantsSlide5

Hybrid speciation

New species form from interspecific hybrids

Two parents

Phylogenetic pattern is reticulate

Enough examples to make it interesting

Not enough to disrupt the generally divergent pattern of phylogenySlide6

Alloploidy

Chromosome doubling (unreduced gametes or somatic doubling)

Alloploid

effectively has one diploid set from each parent species

Instant Speciation™Slide7

Homoploid

hybrid speciation

No chromosome doubling

Two theoretical modes, both documented

Recombinational

speciation

Speciation with external barriersSlide8

Recombinational

speciation

F

1

s of reduced

fertility, chromosome differences

F

2

s more fertile than backcrosses

Fertility restored in new species by recombination of

chromosome

segmentsSlide9

Speciation with external barriers

F

1

s not of reduced fertility

Few or no chromosomal differences between parents

Formation of backcrosses reduced by external barriersSlide10

A long time ago, in a desert close at hand…Slide11

So what’s an

Encelia

?

Asteraceae (sunflower family)

Mostly shrubs

Dry habitats, mostly deserts

Brittlebush (

E.

farinosa

)Slide12

A hybrid under every bush

“The bushes are hybrids”

All species are

interfertile

No apparent reduction of fertility in F

1

, F

2

, backcross

Is it a

syngameon

? Slide13

Spontaneous natural hybrids

E.

farinosa

×

E.

frutescens

E.

farinosa

×

E.

californica

E.

farinosa

×

E.

palmeri

E.

farinosa

×

E.

halimifolia

E.

californica

×

E.

asperifolia

E.

ventorum

×

E.

palmeri

E.

ventorum

×

E.

asperifolia

E.

virginensis

×

E.

frutescens

E.

actoni

×

E.

frutescensSlide14

Encelia

×

laciniata

Named as a species

Hybrids between

E.

ventorum

and

E.

palmeri

Selection against

recombinantsSlide15

Phylogeny: always a good place to start

The days of cladistics before DNA

Two well-defined clades (

californica

clade and

frutescens

clade)

Relationships within clades less clearSlide16

Not just morphology—phenotype

Standard morphology of heads,

capitulescences

, leaves

Micromorphology, especially

trichomes

Secondary chemistry

Ultraviolet floral patterns

Anatomy of stems and leaves (petioles turned out to be useful)

More that I’ve probably forgottenSlide17

Cladograms

based

on phenotypeSlide18

DNA sequence analysis

ITS (internal transcribed spacer of ribosomal DNA)

DNA doesn’t work so well for closely related species

Hybridization is more likely to be confusing in DNA sequence analysis than in morphological analysisSlide19
Slide20

Identifying species of hybrid origin

Species of hybrid origin not always intermediate between parents

Species of intermediate morphology not always of hybrid originSlide21

Preponderance of evidence

Intermediate morphology

Agreement with F

1

s

Apomorphies

shared with parentsSlide22

Species of hybrid origin

E.

virginensis

(parents:

E.

actoni

and

E.

frutescens

subsp.

frutescens

)

E.

asperifolia

(parents:

E. californica

and

E.

frutescens

subsp.

glandulosa

)Slide23

Encelia

virginensisSlide24

E. actoni

E. virginensis

E. frutescensSlide25

Shared phenotypic

apomorphies

–

E.

virginensis

With

E.

frutescens

broad multicellular-based hairs

With

E.

actoni

none

(

E.

actoni

has no clear

autapomorphies

, but

E.

virginensis

resembles it morphologically)Slide26

Agreement with F

1Slide27

length of petiole

width of leaf

height of head

width of head

pedicel width

number of rays

length of ray

length of leafSlide28
Slide29
Slide30

Research by

Gery

AllanSlide31

Chimeric ITS:

E. virginensis

(13 base difference)Slide32

Encelia

asperifoliaSlide33

E. californica

E.

asperifolia

E.

frutescens

subsp.

glandulosaSlide34

Shared phenotypic

apomorphies

–

E.

asperifolia

With

E.

frutescens

broad multicellular-based hairs

no

benzopyrans

or

benzofurans

yellow stigmas

With

E. californica

UV-reflective ray corollas

brown disk corollas

moniliform

hairsSlide35
Slide36

RAPD data:

E. asperifolia

Shared with

E. californica

UBC 218 (0.8 kbase,1.6

kbase

)

UBC 382 (1.4

kbase

)

UBC 409 (0.5

kbase

)

UBC 478 (1.4

kbase

)

Operon B8 (0.75

kbase

)

Shared with

E.

frutescens

UBC 149 (0.7

kbase

)

UBC 375 (1.0

kbase

)Slide37

Chimeric ITS:

E. asperifolia

(21 base difference)Slide38

Hybrid speciation by external barriers

E.

×

laciniata

provides a modelSlide39

Conclusion

I’m done

What are the traits that adapt the new species to their new habitats?

Are there

transgressive

traits?

Plenty of other plant genera Slide40

Acknowledgments

Allan

,

Gery

J

.

Axelrod, Daniel

Braden,

Gerald

Bryant,

Stephen

Budzikiewicz

, Herbert

Carpenter, Kevin J

.

Charest,

Nancy A.

Clark, Emily

Ehleringer

, James R.

Harrington, Daniel F

.

Isman

, Murray B.

Kinney,

Michael

Koukol

, Scott R

.

Kyhos

, Donald W.

Lahmeyer, Sean C

.

Laufenberg, Gabriela

Lee, Gregory J.

Maepo

, Linda

Miller,

David

Nishida, Joy H

.

Panero

, José

Parra,

Mima

Patterson,

Mark

Politt

, Ursula

Proksch

, Peter

Rieseberg

, Loren

Rodriguez,

Eloy

Saccoman

,

Stephanie

Sanders, Donald L

.

Schilling, Edward

Thompson, William C.

Weiler

,

Jeff

Weisman,

Kathy

Wisdom, Charles

Wollenweber

,

Eckhard

Wray,

Victor