Transcript 13 -- Speciation (April 11-15)

Roca et al
2001
Vilgalys 1994
http://botit.botany.wisc.edu/toms_fungi/oct98.html
6
Brown et al. 1999
Brown et al. 1999
Brown et al. 1999
http://atlas.geo.cornell.edu/education/instructor/topography/hawaii_seamounts.html
Mendelson and Shaw 2005
Distinquishing within- vs. between-island speciation
using evolutionary trees
N
M
L
J
K
I
G
H
F
E
C
D
B
A
Within-island speciation
Is land
un ordere d
Kau ai
Oahu
Maui
Hawaii
eq uivocal
Distinquishing within- vs. between-island speciation
using evolutionary trees
G
L
M
H
C
E
K
I
N
F
J
D
B
A
Between-island speciation
Is land
un ordere d
Kau ai
Oahu
Maui
Hawaii
eq uivocal
Ou
tg r
ou
ps
T.
cra
ss
ipe
sM
T.
bid
a
en
sic
o la
Ph
ae
Ka
og
ram
Ph
ma
ae
ns
og
pK
ram
a
T.
ma
joy
vi t
ce
tip
iM
en
o
n is
re t
icu
Mo
l at
ag
al l
pa
er
le a
Ma
ta
ga
l
le r
T.
ce
Ka
la e
no
pte
T.
ra
po
Ha
ha
ku
l
o
T.
aH
pe
a
rki
ns
i
Ka
T.
de
no
tat
aM
T.
a
sw
ez
ey
iM
T.
a
sw
ez
ey
iK
T.
a
lim
p id
ap
ex
Ne
Ma
ote
ph
riti
sp
T.
alu
ar t
em
do
sa
es
eM
ia e
T.
du
a
M
a
ba
uti
ae
T.
Ma
du
ba
uti
ae
T.
Oa
pa
nto
sti
cta
p la
Ha
n ta
g in
ea
T.
se
ap
ed
ica
Mo
lis
Ha
T.
du
ba
uti
ae
T.
Ka
be
ar d
sle
yi
T.
Ma
cra
te r
ico
la
T.
Ma
ar b
o re
ae
Ha
Geographic (island) distribution
Is land
un ordere d
Kau ai
Oahu
Maui
Molo kai
Parsimony reconstruction
Hawaii
Not Ha wa ii
eq uivocal
Host association in Trupanea arboreae
Dubautia linearis
Dubautia arborea
Dubautia ciliolata
Dubautia scabra
Argyroxiphium kauense
http://commons.wikimedia.org/wiki/Commons:Featured_picture_candidates/Image:Hawaii_Island_topographic_map-fr.svg
Mechanisms of
species formation
•
Darwin: geographic
separation followed by
gradual (slow) adaptation to
different ecological
circumstances eventually
leads to reproductive
isolation
•
Two alternatives allow rapid
speciation:
– FOOD: Speciation due
to shifts in host -without geographic
isolation
– SEX: Speciation due to
divergent sexual
selection - with brief
geographic isolation
Model of sympatric speciation
via shifts to new host (FOOD)
2
2
1
2
Host shift
1
Population uses
ancestral host 1
1
New population
founded via shift
to derived host 2
1
2
Populations on two
hosts become
reproductively
isolated
Signatures of sympatric
speciation via host/habitat shift
(after Via 2001)
• Sympatric overlap of host patches
• Mating on the host causes reproductive
isolation between races
• Host phenology differs
• Divergent selection on different
hosts/habitats
Goldenrod gallmaker -- Eurosta solidaginis –
an example of speciation via host-plant shift
Illustration from
Abrahamson and
Weis (1997)
Photo:Warren Abrahamson
Speciation via SEXual selection
Females in
ancestral
populations prefer
blue males
Geographic
barrier divides
populations
Female preference
for male trait
diverges due to
genetic drift
Upon
recontact,
populations
reproductively
isolated due
ONLY to
female
preference
Signatures of speciation via
sexual selection
(after Panhuis et al. 2001)
• Populations within species vary in sexually selected traits
and associated preferences, resulting in partial pre-mating
isolation
• Closely related species differ markedly in mating signals
and preferences, which constitute the primary barrier to
gene exchange
• Species differ in few other traits besides those involved in
mate choice
from Turgeon et al. 2005
North American Enallagma
Turgeon et al. 2005
Damselfly Mating Practices
Photo: Denise Steele, Dartmouth College
McPeek et al. (in press)
Robertson and
Paterson, 1982.
Evolution.
McPeek et al. (in press)
McPeek et al. (in press)
Shape evolution NS different
from “punctuated evolution”
Change in female
shape correlated to
change in male shape
McPeek et al. 2009
Brown, McPeek and May.2000
Syst. Biol. 49:697-712.
Selection and the Enallagma
radiation
• Four damselfly-lake species generated by
habitat shifts and adaptive evolution
(morphological, behavioral and
physiological)
• Many fish-lake species generated during
recent radiations (associated with glacial
retreat?), possibly via founder effects on
mechanical mate recognition system
Shaw and
Lesnick 2009