Part3 life histories - Evolutionary Biologyevolution.unibas.ch/.../pdf/Part3_life_histories.pdf ·...
10
1 The evolution of life histories Outline: Life cycles Variation of life histories (inter- and intra-specific variation) Age / fecundity schedules, life tables and fitness (R 0 and r) Types of life histories Semelparous versus iteroparous Determinate versus indeterminate growth Trade-offs and constraints Experimental tests Directional and stabilising selection Phenotypic plasticity One trait in more detail: The evolution of ageing Part 3 of “Hauptvorlesung Evolutionsbiologie” • Prof. Dieter Ebert & Walter Salzburger • Kontakt: (Verantwortlicher Dozent): [email protected] • Evolutionsbiologie, Zoologisches Institut • Script download @ http://www.evolution.unibas.ch/teaching/index.htm 2 Life cycles The study of life-history evolution involves a quantitative assessment of development throughout the entire life. It mainly concerns aspects related to timing of events, body size, reproduction and survival. Demography plays a central role in our understanding of life history evolution. 3 There is strong variation among species and taxonomic groups in life history traits. Why? 4 There is also strong variation within clades in life history traits.
Transcript of Part3 life histories - Evolutionary Biologyevolution.unibas.ch/.../pdf/Part3_life_histories.pdf ·...
1
The
evol
utio
n of
life
his
torie
sO
utlin
e:Li
fe c
ycle
sVa
riatio
n of
life
his
torie
s (in
ter-
and
intr
a-sp
ecifi
c va
riatio
n)A
ge /
fecu
ndity
sch
edul
es, l
ife ta
bles
and
fitn
ess
(R0
and
r)Ty
pes
of li
fe h
isto
ries
Sem
elpa
rous
vers
us it
erop
arou
sD
eter
min
ate
vers
us in
dete
rmin
ate
grow
thTr
ade-
offs
and
con
stra
ints
Exp
erim
enta
l tes
tsD
irect
iona
l and
sta
bilis
ing
sele
ctio
nPh
enot
ypic
pla
stic
ityO
ne tr
ait i
n m
ore
deta
il: T
he e
volu
tion
of a
gein
g
Part
3 of
“H
aupt
vorle
sung
Evol
utio
nsbi
olog
ie”
•Pr
of. D
iete
r Ebe
rt &
Wal
ter S
alzb
urge
r•
Kon
takt
: (Ve
rant
wor
tlich
erD
ozen
t): d
iete
r.ebe
rt@un
ibas
.ch
•Ev
olut
ions
biol
ogie
, Zoo
logi
sche
sIns
titut
•Sc
ript d
ownl
oad
@
http
://w
ww
.evo
lutio
n.un
ibas
.ch/
teac
hing
/inde
x.ht
m
2
Life
cyc
les
The
stud
y of
life
-his
tory
evo
lutio
n in
volv
es a
qua
ntita
tive
asse
ssm
ent o
f de
velo
pmen
t thr
ough
out t
he e
ntire
life
. It m
ainl
y co
ncer
ns a
spec
ts re
late
d to
tim
ing
of e
vent
s, b
ody
size
, rep
rodu
ctio
n an
d su
rviv
al. D
emog
raph
y pl
ays
a ce
ntra
l rol
e in
our
und
erst
andi
ng o
f life
his
tory
evo
lutio
n.
3
Ther
e is
str
ong
varia
tion
amon
g sp
ecie
s an
d ta
xono
mic
gr
oups
in li
fe
hist
ory
trai
ts.
Why
?
4
Ther
e is
als
o st
rong
var
iatio
n w
ithin
cla
des
in
life
hist
ory
trai
ts.
5
Ther
e is
als
o st
rong
var
iatio
n w
ithin
spe
cies
in
life
his
tory
tr
aits
.
How
can
we
expl
ain
this
?
Plai
ce (H
ippo
glos
soid
espl
ates
soid
es),
Scho
lle
Popu
latio
nSc
ottis
h co
ast
Gra
nd b
anks
New
foun
dlan
d
Age
at m
atur
ity3
year
s15
yea
rs
Size
at m
atur
ity20
cm
40 c
m
Max
. siz
e25
cm
60 c
m
6
Key
eve
nts i
n a
life
cycl
e
Birt
hJu
veni
le p
erio
dG
row
th
Mat
urat
ion
Adu
lt pe
riod
Rep
rodu
ctio
n (+
Gro
wth
)Dea
th
Indi
vidu
al le
vel
Popu
latio
n le
vel
7
Sem
elpa
rity
-rep
rodu
ce o
nce
and
die
-usu
ally
shor
t-liv
ed (a
nnua
l pl
ants
), bu
t sal
mon
and
aga
ve (F
igur
e le
ft) a
re lo
ng li
ved.
Iter
opar
ity: R
epea
ted
repr
oduc
tion
(ver
y co
mm
on)(
e.g.
Dap
hnia
, cod
, ...)
Det
erm
inat
e gr
owth
: Bod
y gr
owth
sto
ps a
fter m
atur
atio
n:
inse
cts,
mos
t mam
mal
s, in
cl.
hum
ans.
Her
ring
C
od
Inde
term
inat
e gr
owth
: Bod
y gr
owth
con
tinue
s af
ter m
atur
atio
n:
pere
nnia
l pla
nts,
man
y fis
h (c
od, f
ar
right
), so
me
crus
tace
ans
(Dap
hnia
, lef
t).
Det
erm
inat
e gr
owth
:Gro
wth
st
op a
t mat
urity
(h
errin
g, ri
ght).
Dap
hnia
Aga
ve
Body weight (kg)
8
2. F
ecun
dity
Spec
ies
Max
. rec
orde
d (o
r es
timat
ed) l
ifetim
e of
fspr
ing
Elep
hant
seal
8R
ed d
eer
14K
ittiw
ake
gull
28 (m
onog
amou
s spe
cies
)H
omo
sapi
ens
69 (i
n 27
pre
gnan
cies
)D
aphn
ia(w
ater
flea)
268
Salm
on>
1 M
illio
nO
ak tr
ee>
10 M
illio
nO
rchi
ds>
1 B
illio
n
Spec
ies
diffe
r in
thei
r de
mog
raph
y
1. S
urvi
val
9
Cal
cula
tion
of th
e ne
t rep
rodu
ctiv
e ra
teR
0: Th
e ne
t rep
rodu
ctiv
e ra
teor
exp
ecte
d lif
etim
e fe
cund
ity is
a m
easu
re o
f fitn
ess:
R0
= m
xl x
= (N
umbe
r of o
ffspr
ing)
x (
prob
abili
ty o
f sur
viva
l to
repr
oduc
tion)
e.g.
a s
alm
onpr
oduc
es 1
0 M
illio
n eg
gs, b
ut h
as a
pro
babi
lity
of e
gg to
adu
lt su
rviv
al
of 1
in 5
Mill
ions
. R0
= 10
'000
'000
X 1
/5'0
00'0
00 =
2
0 <
R0
< 1
popu
latio
n si
ze d
eclin
es.
R0
> 1
popu
latio
n si
ze in
crea
ses.
R
0=
1 co
nsta
nt p
opul
ario
nsi
ze.
R0
= (0
.5 x
0.5
) x 2
.2=
0.55
mx
= 2.
2
l x=
0.25 10
Cal
cula
tion
of th
e ne
t rep
rodu
ctiv
e ra
te
R0
=
For i
tero
paro
usor
gani
sms
we
have
to
add
the
l xmx
valu
es o
f all
repr
oduc
tive
age
clas
ses.
l x an
d m
xar
e ca
lcul
ated
per
ca
pita
.
R0
= 6
l xmx
Bar
nacl
es (S
eepo
cken
)
Num
ber
aliv
e
11
Ano
ther
exa
mpl
e: a
per
enni
al p
lant
l xmx
025
7.1
387.
516
1.2
35.9
3.8
0.54
0.04
____
___
6=
846
R0
= 84
6
This
is w
hat i
s us
ed
to p
repa
re a
n ag
e hi
stog
ram
.
, lx
, mx
12
Cal
cula
tion
of th
e M
alth
usia
n pa
ram
eter
A d
iffer
ent w
ay to
cal
cula
te p
opul
atio
n gr
owth
is th
e M
alth
usia
n pa
ram
eter
.
r : M
athu
sian
para
met
er(a
fter T
hom
as M
alth
us) i
s the
rate
of i
ncre
ase
for a
giv
en li
fe
tabl
e. It
is so
met
imes
als
o ca
lled
the
popu
latio
n gr
owth
rat
e.
r = lo
g e( N
(t)/ N
(t-1)
)
In 1
998,
a p
opul
atio
n ha
d a
size
of 8
50, o
ne y
ear l
ater
it re
ache
d 10
00.
The
popu
latio
n gr
owth
rate
dur
ing
this
per
iod
was
:
r = lo
g e( N
(t)/ N
(t-1)
) =
log e
(100
0 / 8
50) =
0.1
6 in
divi
dual
s per
ind.
per y
r.Th
is is
abo
ut a
n in
crea
se o
f 16%
per
yea
r.
ris c
alcu
late
d fo
r spe
cific
tim
e in
terv
als.
In th
is e
xam
ple:
a y
early
gro
wth
rate
. r=
0 in
dica
tes z
ero
grow
th.
r< 0
indi
cate
s a d
eclin
e in
pop
. siz
e.
r> 0
an
incr
ease
in p
op. s
ize.
13
Cal
cula
tion
of th
e M
alth
usia
n pa
ram
eter
from
a li
fe ta
ble
x (A
ge)
lxm
xlx
mx
r0
10
00.0368
10.
252
0.5
20.
15
0.5
30.
032
0.06
40
00
Whi
le th
e ca
lcul
atio
n of
R0
is s
traig
ht fo
rwar
d (th
e su
m o
f all
l xm
x), th
e ca
lcul
atio
n of
ris
mor
e co
mpl
icat
ed. T
he E
uler
-Lot
kaeq
uatio
n ca
n on
ly b
e so
lved
ana
lytic
ally
for s
peci
al c
ases
. U
sual
ly it
is s
olve
d nu
mer
ical
ly w
ith th
e he
lp o
f com
pute
r pro
gram
s. T
he s
impl
est w
ay is
to
gues
s a
valu
e fo
r ran
d ca
lcul
ate
the
right
han
d te
rm. I
f it i
s di
ffere
nt fr
om 1
you
cha
nge
rac
cord
ingl
y an
d try
aga
in. R
epea
t thi
s un
til y
ou fi
nd th
e va
lue
for r
whi
ch s
atis
fies
the
equa
tion.
For
a n
ice
prog
ram
(fre
ewar
e) s
ee:
http
://w
ww
.cbs
.um
n.ed
u/po
pulu
s/(lo
okun
der"
sing
lesp
ecie
sdy
nam
ics"
and
than
"age
stru
cter
edgr
owth
".)
R0
= 6
l xmx
= ����
Eule
r-Lo
tka
equa
tion:
1 = 6
e-rx
l x m
x
A hy
poth
etic
al li
fe h
isto
ry:
14
Som
e pr
oper
ties
rand
R0:
The
effe
ct o
f del
ayed
mat
urity
x (A
ge)
lxm
xlx
mx
rR
o0
10
01.15
101
10
02
110
103
00
0
01
00
0.77
101
10
02
10
03
110
104
00
0
01
00
0.57
101
10
02
10
03
10
04
110
105
00
0
In th
ese
3 hy
poth
etic
al e
xam
ples
su
rviv
al is
max
imal
(1.0
) unt
il re
prod
uctio
n. R
epro
duct
ion
occu
rs o
nce
(10
offs
prin
g,
follo
wed
by
deat
h). A
ge a
t m
atur
ity is
2, 3
and
4 y
ears
in th
e th
ree
life
tabl
es. N
ever
thel
ess,
all
thre
e lif
e ta
bles
resu
lt in
an
R0
of
10. I
n co
ntra
st, r
decl
ines
stro
ngly
w
hen
age
at m
atur
ity is
del
ayed
. Th
e po
pula
tion
grow
th ra
te is
ve
ry s
ensi
tive
to a
ge a
t firs
t re
prod
uctio
n.
This
effe
ct m
ay b
e co
mpe
nsat
ed
whe
n de
laye
d m
atur
ity re
sults
in
high
er fe
cund
ity, w
hich
is o
ften
the
case
.
15
rand
R0
can
be u
sed
as fi
tnes
s mea
sure
sTh
ey a
llow
to p
redi
ct li
fe h
isto
ries
The
idea
is th
at a
gen
otyp
e w
ith a
hig
her g
row
th ra
te is
abl
e to
out
-gro
w
othe
r gen
otyp
es w
ith a
low
er g
row
th ra
te.
ris u
sed
for s
peci
es w
ith o
verla
ppin
g ge
nera
tions
.
R 0is
use
d fo
r sem
elpa
rous
spec
ies o
r spe
cies
with
non
-ove
rlapp
ing
gene
ratio
ns.
Not
e: A
s pop
ulat
ion
grow
th is
det
erm
ined
by
repr
oduc
tion,
it is
usu
ally
ca
lcul
ated
for f
emal
es o
nly.
Usu
ally
fem
ale
fecu
ndity
lim
its th
e gr
owth
of
a po
pula
tion.
16
Opt
imal
age
at m
atur
ity fo
r sem
elpa
rous
orga
nism
s
R0
= (N
umbe
r of o
ffspr
ing,
m)
x (p
roba
bilit
y of
sur
viva
l to
mat
urity
, l(D�)
Ass
ume
that
in a
sem
elpa
rous
spec
ies
fecu
ndity
incr
ease
s w
ith a
ge a
t mat
urity
.H
owev
er, t
he c
hanc
e to
sur
vive
unt
il m
atur
ity d
ecre
ases
if m
atur
ity is
del
ayed
. W
hat i
s th
e op
timal
age
at m
atur
ity?
Fecu
ndity
Surv
ival
Opt
imal
age
at m
atur
ity, D
Per
gen
erat
ion
fitne
ss, R
0fo
r a
sem
elpa
rous
org
anis
m in
w
hich
fecu
ndity
, m, i
ncre
ases
w
ith a
ge a
t mat
urity
(D).
The
prob
abili
ty o
f sur
vivi
ng to
re
prod
uce,
l, d
ecre
ases
eve
n if
the
mor
talit
y ra
te is
con
stan
t.
17
ras a
fitn
ess m
easu
re a
llow
s to
pred
ict l
ife h
isto
ries
For s
alam
ande
rs, d
elay
ed
mat
urity
resu
lts in
hig
her
fecu
ndity
. Thi
s le
ads
to a
th
eore
tical
fitn
ess
max
imum
of
5 y
ears
at m
atur
ity. I
n na
ture
, H. n
ebul
osus
mat
ures
af
ter 5
yr.
Opt
imal
age
at
mat
urity
Clou
ded
Sala
man
der,
Hyno
biusn
ebulo
sus
Opt
imal
age
at m
atur
ity fo
r ite
ropa
rous
orga
nism
s
Est
imat
ed re
latio
nshi
p be
twee
n fit
ness
(r) a
nd th
e ag
e at
firs
t re
prod
uctio
n in
the
clou
ded
sala
man
der (
from
Kus
ano
1982
).
18
Whe
n be
iter
opar
ous a
nd w
hen
sem
elpa
rous
? (1
)In
a fi
rst a
ppro
xim
atio
n, it
app
ears
that
repe
ated
bre
edin
g m
ust b
e be
nefic
ial.
Is th
is s
till s
o if
bein
g ite
ropa
rous
has
cos
ts in
term
s of
redu
ced
year
ly fe
cund
ity?
Rat
io o
fye
arly
fecu
ndity
for i
tero
paro
us/
sem
elpa
rous
st
rate
gy
Alw
ays
be it
erop
arou
s if
ther
e ar
e no
fe
cund
ity c
osts
(m
i=m
s=1)
. Oth
erw
ise,
be
iter
opar
ous
if th
e ch
ance
to re
prod
uce
agai
n is
hig
h (i.
e. h
igh
adul
t sur
viva
l) an
d th
e an
nual
pop
ulat
ion
grow
th ra
te (h
ere
give
n as
lam
bda)
is lo
w.
Pop
ulat
ion
grow
th ra
te
19
Whe
n be
iter
opar
ous a
nd w
hen
sem
elpa
rous
? (2
)
A co
mpa
rison
bet
wee
n ite
ropa
rous
(per
enni
al) g
rass
sp
ecie
s an
d se
mel
paro
us(a
nnua
l) gr
ass
spec
ies
show
s th
at p
eren
nial
s in
vest
less
in
repr
oduc
tion
(low
er
repr
oduc
tive
effo
rt, i.
e. lo
wer
pr
opor
tion
of b
iom
ass
inve
sted
in
flow
ers)
. Thi
s ho
lds
true
even
if w
e co
rrect
for p
lant
si
ze. T
hus,
iter
opar
ous
gras
ses
inve
st m
ore
in g
row
th
and
less
in re
prod
uctio
n. T
his
is n
eces
sary
to s
urvi
ve to
the
next
yea
r.
20
Doe
s th
e m
orta
lity
rate
influ
ence
the
evol
utio
n of
life
his
tory
trai
ts?
The
evol
utio
n of
gup
py li
fe h
isto
ry in
resp
onse
to p
reda
tion
Gup
py (P
oeci
liare
ticul
ata)
Cor
rela
tion
betw
een
pred
atio
n re
gim
e an
d lif
e hi
stor
y tr
aits
in G
uppi
es
Two
pred
ator
s:C
reni
cich
laal
ta: p
reys
on
larg
e, m
atur
e gu
ppie
sR
ivul
usha
rtii:
prey
s on
sm
all g
uppi
es
Gup
pies
from
Cre
nici
chla
site
s:-m
atur
e at
ear
lier a
ge a
nd s
mal
ler s
ize
-hav
e a
high
er re
prod
uctiv
e ef
fort
-hav
e m
ore
and
smal
ler o
ffspr
ing
per b
rood
than
Gup
pies
from
Riv
ulus
site
s.
Are
thes
e di
ffere
nces
due
to n
atur
al s
elec
tion
impo
sed
by th
e di
ffere
nt p
reda
tors
influ
enci
ng
the
dem
ogra
phy
(age
dep
ende
nt fe
cund
ity a
nd
surv
ival
)?
Cre
nici
chla
alta
Riv
ulus
hart
ii
21
Expe
rimen
tal e
volu
tion
in th
e fie
ld:
1976
: 200
indi
vidu
als
from
a s
ite w
ith h
igh
adul
t mor
talit
y (p
reda
tor C
reni
cich
la)w
ere
used
to e
stab
lish
a ne
w p
opul
atio
n at
a s
ite w
ith R
ivul
us(p
reys
on
smal
l gup
pies
). 19
87: t
he n
ew p
opul
atio
n co
mpa
red
with
the
ance
stra
l one
Trai
tC
ontr
olC
reni
cich
laIn
trod
uctio
nR
ivul
usSt
atis
tical
sign
ifica
nce
Mal
e ag
e at
mat
urity
48.5
58.2
p <
0.01
Mal
e si
ze a
t mat
urity
67.5
76.1
p <
0.01
Fem
ale
age
at m
atur
ity85
.792
.3p
< 0.
05Fe
mal
e si
ze a
tm
atur
ity16
1.5
185.
6p
< 0.
01
Siz
e of
litte
r 14.
53.
3p
< 0.
05O
ffspr
ing
wei
ght l
itter
10.
870.
95p
< 0.
1R
epro
duct
ive
effo
rt22
.018
.5N
S
The
intr
oduc
ed p
opul
atio
n ev
olve
d in
the
pred
icte
d di
rect
ion.
Pr
edat
ion
regi
me
affe
cts
the
evol
utio
n of
life
his
tory
trai
ts.
Doe
s th
e m
orta
lity
rate
influ
ence
the
evol
utio
n of
life
his
tory
trai
ts?
The
evol
utio
n of
gup
py li
fe h
isto
ry in
resp
onse
to p
reda
tion
22
The
role
of t
rade
-offs
in li
fe h
isto
ry e
volu
tion
Trad
e-of
f: a
rela
tions
hip
betw
een
fitne
ss re
late
d tra
its (f
itnes
s co
mpo
nent
s) s
uch
that
a c
hang
e in
one
trai
t in
the
dire
ctio
n of
hig
her f
itnes
s is
ass
ocia
ted
with
the
chan
ge in
the
dire
ctio
n of
low
er fi
tnes
s in
oth
er tr
aits
. The
y re
flect
cos
ts o
f ad
apta
tions
.
For e
xam
ple,
ther
e m
ay b
e a
trade
-off
betw
een
the
tota
l num
ber o
f egg
s pr
oduc
ed a
nd th
e av
erag
e eg
g si
ze. T
hus,
incr
easi
ng e
gg s
ize
wou
ld h
ave
cost
s in
term
s of
redu
ced
egg
num
ber.
Pro
duci
ng m
ore
eggs
wou
ld re
sult
in s
mal
ler
eggs
.
Num
ber o
f egg
s
Size of
eggs
23
Clu
tton-
Bro
ck e
t al 1
982
Trad
e-of
f: C
ost o
f rep
rodu
ctio
nA
mon
g th
e m
ost c
omm
only
obs
erve
d tra
de-o
ffs i
s the
cos
t of r
epro
duct
ion.
24
Bro
ods
redu
ced
or e
nlar
ged
by tr
ansf
errin
g 1-
3 eg
gs te
n da
ysaf
ter
layi
ng
Bro
od:
Red
uced
Con
trol
Enl
arge
d
num
ber
of b
rood
s:28
5420
mea
n cl
utch
siz
e:5.
255.
195.
40m
ean
chan
ge in
bro
od s
ize:
–1.7
40.
00+2
.51
mea
n nu
mbe
r fle
dged
:2.
603.
955.
84V
c - r
epro
duct
ive
valu
e of
clu
tch
2.52
4.20
5.59
Par
ents
:Lo
cal p
aren
tal s
urvi
val,
p1:
0.65
0.59
0.43
Vp
- re
sidu
al r
epro
duct
ive
valu
e:9.
888.
896.
49
Tota
l:V
- to
tal r
epro
duct
ive
valu
e:12
.40
13.0
912
.08
Sou
rce:
Daa
n et
al.
1990
Expe
rimen
tal p
heno
type
man
ipul
atio
n:
cost
of r
epro
duct
ion
in k
estr
el (F
alco
tinn
uncu
lus)
Is th
e cl
utch
siz
e la
id b
y ke
stre
ls in
fluen
ced
by tr
ade-
offs
? Clu
tch
size
laid
by
the
kest
rels
max
imiz
es th
eir
fitne
ss (r
epro
duct
ive
valu
e). T
his
is b
roug
ht
abou
t by
a tra
de-o
ff be
twee
n cu
rren
t re
prod
uctio
n an
d su
rviv
al.
Rep
rodu
ctiv
e va
lue:
an
inde
x m
easu
ring
expe
cted
ge
netic
con
tribu
tion
to fu
ture
gen
erat
ions
Num
ber o
f egg
s
Sur
viva
lof
pare
nts
25
How
man
y eg
gs sh
ould
a b
ird p
rodu
ce?
As m
any
as p
ossi
ble?
Gre
at ti
ts p
rodu
ce, o
n av
erag
e, 8
.5 e
ggs.
5 6 7 8 9 10 11 12
120
100 80 60 40 20 0
Num
ber
ofcl
utch
es
Clu
tch
size
0 2 4 6 8 10 12 14
Wei
ght/
chic
k
Clu
tch
size
Weight per chick (g)
Surv
ival
until
3 m
onth
s
Mul
tiple
trad
e-of
fs in
Gre
at ti
ts
26
5 6 7 8 9 10 11 12
Num
ber
ofcl
utch
es
Clu
tch
size
0 2 4 6 8 10 12 14
Rec
aptu
repe
r clu
tch
one
year
la
ter
Clu
tch
size
1.0
0.8
0.6
0.4
0.2
0.0
Clu
tch
size
s bet
wee
n 8
and
12eg
gs le
ave
the
mos
t sur
vivi
ng o
ffspr
ing
The
trade
-off
betw
een
offs
prin
g nu
mbe
r and
surv
ival
alo
ne d
oes n
ot e
xpla
in th
e cl
utch
size
in g
reat
tits
. Wha
t abo
ut th
e su
rviv
al o
f the
mot
her?
Doe
s she
suffe
r fr
om a
cos
t of r
epro
duct
ion?
Mul
tiple
trad
e-of
fs in
Gre
at ti
ts
27
Mot
her
surv
ival
to th
ene
xt y
ear
0 2 4 6 8 10 12 14
Clu
tch
size
0.8
0.6
0.4
0.2
0.0
Gre
at ti
ts w
ith la
rge
clut
ches
hav
e a
low
er c
hanc
e to
repr
oduc
e th
e fo
llow
ing
year
. Thi
s ind
icat
es a
co
st o
f rep
rodu
ctio
n.
Mul
tiple
trad
e-of
fs in
Gre
at ti
ts
Opt
imal
clu
tch
size
The
optim
um is
onl
y ap
pare
nt a
fter t
akin
g in
to a
ccou
nt tr
ade-
offs
with
juve
nile
and
pa
rent
al s
urvi
val.
Furth
er re
sear
ch in
dica
ted
that
yea
r to
year
var
iatio
n in
clim
atic
co
nditi
ons
play
a ro
le. I
n a
bad
year
, it i
s le
ss c
ostly
to p
rodu
ce to
o fe
w e
ggs.
From
Boy
ce &
Per
rins
1987
28
Trad
e-of
f bet
wee
n m
atin
g an
d lo
ngev
ity in
mal
e fr
uit
flies
(Dro
soph
ila m
elan
ogas
ter)
From
: Par
tridg
e an
d Fa
rquh
ar 1
981
In o
ne tr
eatm
ent,
mal
es w
ere
regu
larly
sup
plie
d w
ith v
irgin
fem
ales
, so
they
mat
ed
man
y tim
es. I
n th
e ot
her,
they
wer
e gi
ven
mat
ed fe
mal
es w
hich
are
usu
ally
not
re
cept
ive.
Freq
uent
mat
ing
redu
ced
mal
e lo
ngev
ity. T
he s
ame
hold
s fo
r fem
ales
(not
sho
wn)
.
Mal
eLo
ngev
ity(d
ays)
Inse
min
ated
fem
ales
adde
d
Virg
inFe
mal
es a
dded
29
Evol
utio
nary
trad
e-of
f bet
wee
n le
arni
ng a
bilit
y an
d co
mpe
titiv
e ab
ility
in D
roso
phila
mel
anog
aste
rFr
uit f
ly p
opul
atio
ns w
ere
sele
cted
for i
mpr
oved
lear
ning
for a
lmos
t 50
gene
ratio
ns ("
sele
cted
"); o
ther
line
s ("
cont
rols
") w
ere
mai
ntai
ned
with
out
sele
ctio
n.
Inte
llige
nt fl
ies
lose
in c
ompe
titio
n fo
r lim
ited
food
.
0
0.1
0.2
0.3
cont
rol
sele
cted
for
impr
oved
lear
ning
Learning score
sele
cted
for
impr
oved
lear
ning
cont
rol
Larval competitive ability
orig
inal
line
scr
osse
s be
twee
n lin
es
From
: Mer
y an
d K
awec
ki 2
003
30
Evol
utio
nary
trad
e-of
f bet
wee
n ph
otot
roph
y an
d he
tero
trop
hy in
the
gree
n al
ga C
hlam
ydom
onas
Chl
amyd
omon
asis
cap
able
of b
oth
phot
osyn
thes
is (i
f the
re is
eno
ugh
light
) and
he
tero
troph
y. R
ebou
d an
d B
ell (
1997
) mai
ntai
ned
som
e lin
es fo
r man
y ge
nera
tions
in
the
pres
ence
of l
ight
and
oth
er li
nes
in th
e da
rk o
n a
med
ium
with
a s
ugar
sou
rce.
Each
line
had
a
redu
ced
fitne
ss in
th
e ot
her
envi
ronm
ent
110100
1000
12
Ass
ay e
nviro
nmen
t
Fitness
Dar
kLi
ght
Line
s ev
olve
d w
ith li
ght
Line
s ev
olve
d in
dar
knes
s
31
Det
ectin
g tr
ade-
offs
in s
elec
tion
expe
rimen
tsS
elec
tion
in th
e di
rect
ion
of im
prov
ed fi
tnes
s.
sele
ctio
n
sele
ctio
n
Sel
ectio
n to
war
ds d
ecre
ased
fitn
ess
may
favo
urde
lete
rious
gen
otyp
es:
trait 2
trait
1
trait 2
trait
1
trait 2
trait
1
32
Dire
ctio
nal a
nd st
abili
sing
sele
ctio
nG
uppi
es e
volv
ed a
n al
tere
d lif
e hi
stor
y w
hen
intro
duce
d to
a s
ite w
ith a
di
ffere
nt m
orta
lity
regi
me.
Sel
ectio
n ac
ted
in o
ne d
irect
ion.
Thi
s is
cal
led
dire
ctio
nal s
elec
tion.
It is
mos
t co
mm
only
foun
d af
ter a
cha
nge
in th
e en
viro
nmen
tal c
ondi
tions
. Tr
ait v
alue
Fitn
ess
Trai
t val
ue
Fitn
ess
Trai
t val
ue
Fitn
ess
The
fitne
ss o
f kes
trels
was
low
er w
hen
the
clut
ch s
ize
was
eith
er re
duce
d or
enl
arge
d. T
he c
lutc
h si
ze in
ke
stre
ls s
eem
s to
be
unde
r sta
bilis
ing
sele
ctio
n, i.
e.
devi
atio
ns in
bot
h di
rect
ions
from
the
optim
um re
sult
in
low
er fi
tnes
s. S
tabi
lisin
g se
lect
ion
is th
e ru
le fo
r mos
t life
hi
stor
y tra
its, o
nce
they
are
nea
r the
ir op
timum
. Ofte
n,
trade
-offs
are
invo
lved
.
33
Stab
ilisi
ng s
elec
tion.
Ext
rem
es a
re s
elec
ted
agai
nst
Bab
ies
of to
o hi
gh o
r too
low
wei
ght a
t birt
h fa
ce a
hi
gher
mor
talit
y. M
orta
lity
of to
o la
rge
babi
es is
in
part
caus
ed b
y de
ath
of m
othe
r at b
irth.
Thu
s, b
irth
wei
ght i
n hu
man
s is
und
er s
tabi
lisin
g se
lect
ion,
with
op
timal
birt
h w
eigh
t of a
bout
3.5
kg
Infa
nt m
orta
lity
as a
func
tion
of a
m
othe
r’s a
ge. U
nite
d S
tate
s 19
60-6
1,
107'
038
infa
nts.
Eac
h po
int i
s a
5 ye
ar
age
clas
s. B
abie
s of
mot
hers
age
d 20
to
35 h
ave
the
high
est s
urvi
val c
hanc
e.
From
Ste
arns
& H
oeks
tra 2
000.
34
Opt
imal
tim
e to
kill
the
hos
t
35
Phen
otyp
ic p
last
icity
The
abili
ty o
f a g
enot
ype
to e
xpre
ss (p
rodu
ce) d
iffer
ent p
heno
type
s de
pend
ing
on
envi
ronm
enta
l con
ditio
ns.
Pla
stic
ity m
ay b
e a
dire
ct re
sults
of e
nviro
nmen
tal i
nflu
ence
s or
an
evol
ved
adap
tive
resp
onse
.Pl
astic
ity o
f a b
ehav
iora
l tra
itW
ebs
spun
by
spid
er P
araw
ixia
bis
triat
aat
nig
ht
(left)
and
at d
ay d
urin
g te
rmite
sw
arm
ing
(righ
t)
San
dova
l 199
4
Sub
mer
ged
Air-
wat
erA
eria
lin
terfa
ce
Plas
ticity
of a
mor
phol
ogic
al c
hara
cter
Leaf
sha
pe in
Ran
nunc
ulus
aqu
atili
s
36
Phen
otyp
ic p
last
icity
: pr
edat
or in
duce
d de
fenc
eD
aphn
iaar
e pl
ankt
onic
cru
stac
eans
(0.5
-5 m
m),
whi
ch
are
ofte
n ea
ten
by fi
sh. F
ish
pred
atio
n va
ries
stro
ngly
th
roug
h th
e se
ason
s. T
here
fore
, it i
s ad
vant
ageo
us to
pr
oduc
e th
e co
stly
def
ensi
ve s
truct
ures
onl
y in
the
pres
ence
of f
ish.
Thi
s is
wha
t Dap
hnia
does
. Whe
n th
ey
"sm
ell"
the
pres
ence
of f
ish,
they
dev
elop
def
ensi
ve
spin
es. E
xper
imen
t con
firm
ed th
at s
pine
s ar
e pr
otec
tive
and
that
thei
r pro
duct
ion
is c
ostly
. In
the
pres
ence
of
fish,
Dap
hnia
mat
ure
earli
er a
nd a
t a s
mal
ler s
ize.
Def
ensi
vest
ruct
ures
D. l
ongi
ceph
ala
D. p
ulex
The
very
left
and
the
very
rig
ht D
aphn
ia
are
fish-
smel
l in
duce
d fo
rms.
37
Phen
otyp
ic p
last
icity
: pre
dato
r ind
uced
def
ence
In th
e pr
esen
ce o
f fis
h, D
aphn
iam
atur
e at
a s
mal
ler s
ize
and
an e
arlie
r age
. In
this
way
, the
y re
duce
the
elev
ated
fitn
ess
cost
s du
e to
incr
ease
d ad
ult
mor
talit
y ca
used
by
fish
pred
atio
n. F
ish
pref
er la
rger
Dap
hnia
. Th
e of
fspr
ing
prod
uced
by
fish
expo
sed
Dap
hnia
is a
lread
y sm
alle
r at b
irth.
Size
Tim
e
Mat
urity
Offs
prin
gsi
ze at birth
No
fish
38
Plas
ticity
(pol
yphe
nism
) of w
ing
patte
rn in
Bic
yclu
s an
ynan
a
Pol
yphe
nism
= p
last
icity
with
two
mai
n ph
enot
ypes
and
few
inte
rmed
iate
s
Dry
sea
son
phen
otyp
e (D
in fi
gure
). D
evel
ops
at ~
20°C
, Pal
e, c
rypt
ic,
rest
s on
leaf
litte
r
Wet
sea
son
phen
otyp
e (W
in fi
gure
). D
evel
ops
at
~27°
C, d
ark,
larg
e ey
espo
ts, a
ctiv
e
Art
ifici
al s
elec
tion
for l
arge
and
sm
all e
ye s
pots
at 2
0 °C
The
reac
tion
norm
s fo
r eye
spo
t siz
e di
ffer l
ittle
in s
hape
. The
y m
ay
be c
onst
rain
t.
Mea
n po
pula
tion
reac
tion
norm
s Uns
elec
ted
(Con
trol)
Sel
ecte
d fo
rla
rge
spot
s
Sel
ecte
d fo
rsm
all s
pots
Bra
kefie
ld e
t al.
1996
W/D
: Wet
and
dry
sea
son
form
in th
e fie
ld
39
Why
are
ther
e tr
aits
whi
ch s
eem
to d
evia
te fr
om th
e op
timum
?
Som
e po
ssib
le re
ason
s:1.
Opt
imum
is n
ot y
et re
ache
d (e
.g. t
he e
nviro
nmen
t cha
nged
re
cent
ly) “
The
mis
mat
ch h
ypot
hesi
s”2.
Gen
e flo
w b
etw
een
popu
latio
ns (i
nflo
w o
f bad
gen
es)
3.M
utat
ion
-sel
ectio
n ba
lanc
e (n
ew m
utat
ions
occ
ur a
t the
sam
e ra
te th
at s
elec
tion
acts
aga
inst
them
).4.
Con
stra
ints
(phy
sica
l, ch
emic
al, m
echa
nica
l, or
oth
er) p
reve
nt
evol
utio
n to
reac
h th
e op
timum
.5.
Unr
ecog
nize
d tra
de-o
ffs p
reve
nt e
volu
tion
to re
ach
the
optim
um.
6.C
ost -
bene
fit a
naly
sis
mis
ses
an im
porta
nt a
spec
t.7.
Ant
agon
istic
coe
volu
tion
(the
optim
um is
a m
ovin
g ta
rget
)8.
Trai
ts m
ay b
e m
isun
ders
tood
(e.g
. Nau
sea,
feve
r, vo
miti
ng,
coug
hing
, anx
iety
, etc
. ar
e pa
infu
l, bu
t may
be
usef
ul)
