Telling the Evolutionary Time: Molecular Clocks and the Fossil Record

(Grace) #1
ANGIOSPERM DIVERGENCE 153

Th


e f


os


sil



  • b


as
ed


es


tim


ates


a
re


, c


ont


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ry


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ss
um


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um


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th


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t b


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e t


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n q


ue


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ion a


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ts s


ist


er g


rou


p.


Co

lum

n^1

li

sts

t
he ta

xa

a

cc

ordi

ng

t

o th

eir u

sa
ge

, a

nd c

olum

ns

2–

5 li

st our a

ge

es

tim

ates

(
no

de nu

m
bers

c

orres

pon

d to t

ho

se

on t

he

c

hro

nog

ra
m

s,

Fig

ures

8.3

-^8


.6)

. T


he

a
ge s

pa

n g

iv
en

in

c
ol
um

n 2 r

es

ults

fr

om

th

e th

ree

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ons

ec

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ve

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g A

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TR

A
N
an

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EL

TR

AN

opt

im

iza

tio

n a

nd m

axi

m
um

lik

eli

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od f

or

ca
lc
ul

ati

ng

b

ra
nc

h^

le
ng

th

s.^

Th

e^

sp

ec

ifi

c a

ges

, r

es

ulti

ng

fr

om

e

ac
h a

na

ly
sis

a

re

re

port

ed i

n c

olum

ns

3–


  1. C


ol

um

n^

6 i

ndi

ca

tes

t
he

b

oots

tra

p

es
tim

at
es

of

sta

nd

ard

error

, a

nd c

ol
um

ns

7–

8 li

st

fo
ss
il-

ba

se

d es

tim

ates

ext

ra
ct
ed f

rom

M

ag

all

ón

et^

al

. (


1 999)

an

d M

ag

allón

an

d S

ande

rs
on (

2001

).

Th

e s

pec

ifi
c

fo

ssi

l-
ba

se
d a

ge

(c

ol

um

n 7)

c
orre

sp

onds

to th

at g

ive

n b

y M

ag

alló

n
et^

al.

(^1999

) a

nd M

ag

alló

n a

nd

S
ander

son

(^2

0 01)

a
nd

a
lso

in

di
ca
te

s on w

ha

t ta

xon t

he

ag

e

es

tim

at
e w

as
b
as
ed.

C

ol

um

n^8

lis

ts i

ns

ta
nc

es
w

hen

th

e t

opol

og

y i

m

pl
ie
s th

at s

om

e^
oth

er

fo
ss
il p

rov

id
es

a b

et

ter

m

ini

m
um

ag

e es

tim

ate f

or

a^ nod

e. I

n a

ddi

tio

n,

fu

rt
he

r
co

m

pa

ris

on

s^
ar
e m

ade w

he

nev

er

th

e f

os

sil


  • b


as
ed

es

tim

at
e w

as
b

as
ed on

a
le

ss
in

clus

iv
e ta

xon.

T

he

ag

e

fo
r th

e

Ar

istolo

ch

iace

ae


  • L


act

or

id
ace

ae

cl

ad

e,

fo

r exa

m
pl
e,

w
as
b
as
ed o

n L

ac

tori

da

ce

ae

pol

len

(
Za

va

da

1987

).

W

e h

av

e^

th
ere

fo
re

in
clud

ed

co

m
pa

ri
so

ns
w

ith

b

oth

t
he A

ri
sto

loc

hi
ac
eae

-L

ac

to

rid

ac

eae

a
nd

La

ct
or

id
ac

ea

e cl

ad

es
.

a T

he f

os

sil


  • b


as
ed a

ge

co

nc

erns

th

e s

tem


  • g


rou

p a

nd not

th

e c

row

n-

gr
oup a

s f

or

rem

aini

ng

ta

xa

(M

ag

all

ón a

nd S

an

ders

on 2

001)

.

b W

e^
ar
e u

na

bl
e^
to

c
om

pa

re
th

e f

os
sil


  • b


as
ed

e
sti

m
ate

fo

r^ th

e l

es
s i

nc

lu
siv

e
ta
xo

n^
w
ith

a
m

ol
ec

ul
ar

es

tim

ate

si

nc

e
th

e t

axo

n w

as
not

in

cl
ude

d i

n th

e m

ole

cu

la
r

da

ta
se

t.

c M

ag

al
lón

et^

al.

(
199

9)
ind

ica

te

d a

n

Ap

tia

n (

124

.5–

11

2 M

a)
oc

curr

enc

e^
for

Po

pu

lu

s p

oto

ma

ce
ns
is,

b

ut

th

e or

ig
in
al^

doc

um

enta

tio

n of

th

is ta

xon

in

di
ca

te
d

th

e

Al

bi
an

(^1

12


  • 97 M


a; D

oy

le
an

d H

ic
key

1976

).
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