Sexual selection and speciation: field
crickets as a model system
David A. Gray
California State University, Northridge
The Cricket Mating System
Cryptic sister species:
Gryllus texensis and Gryllus
rubens
Geographic Ranges
Male pulse rates
(field matings, N = 451)
70
60
50
40
30
20
10
0
45
50
55
60
65
70
pulse rate @ 25 C
75
80
85
90
95
Lab hybrid songs
Quantitative genetics: G. texensis
• ‘Meta-population’ heritability
– Male song h2 = 0.40 + 0.16 *
– Female preference h2 = 0.38 + 0.17 *
• Genetic correlation
– rG = 0.49 + 0.23 *
• * Estimates greater than zero.
Courtship as a pre-mating isolating
mechanism?
• Geographic variation
in courtship
• Sound and Smell
– Muted males
– Song playback
568 trials completed……
Males
Exact, P1-tailed < 0.000).
90
80
Percent Male Courtship
G. rubens (Fisher’s
G. rubens
100
G. texensis (Fisher’s
70
60
Cons pecific female
Heteros pecific female
50
40
30
20
10
0
Allopatry
Exact, P1-tailed = 0.073)
Allo/Sym NS
Sy mpatry
G. texensis
100
90
Percent Male Courtship
80
70
60
Cons pecific female
Heteros pecific female
50
40
30
20
10
0
Allopatry
Sy mpatry
Species of Male:(Fisher’s
Exact, G. rubens P1-tailed = 0.028,
G. texensis P1-tailed = 0.000)
% fem ales mou nting
Females
80
60
20
0
G. rubens male
G. tex ensis male
G. rubens male
G. tex ensis male
G. rubens s ong
G. rubens s ong
G. tex ensis song
G. tex ensis song
G. texensis females
100
% fem al es mo untin g
Allo/Sym NS
Allopatry
Sy mpatry
40
Courtship song played:
(Fisher’s Exact, G. rubens P1-tailed
= 0.000, G. texensis P1-tailed =
0.000)
G. rubens females
100
80
60
Allopatry
Sy mpatry
40
20
0
G. rubens male
G. tex ensis male
G. rubens male
G. tex ensis male
G. rubens s ong
G. rubens s ong
G. tex ensis song
G. tex ensis song
M ale Son g and Species Combination
Questions answerable (?) with
DNA sequence data
• Extent of recent hybridization
• Population history (expansion, isolation by
distance)
• Geographic context of speciation
• DATA
 177 G. rubens from 25 localities
 188 G. texensis from 23 localities
 724 bp mtDNA Cytochrome C Oxidase subunit I (COI)
• G. texensis
164 haplotypes (N = 188)
• G. rubens
27 haplotypes (N = 177)
AMOVA
Between species 10.22%
P < 0.0001
Other Results
• No evidence of significant hybridization
• G. texensis
– No geographic isolation by distance
– No recent population expansion
• G. rubens
– Recent population expansion (P < 0.02)
– Geographic expansion with significant isolation by
distance (P < 0.02)
Geographic scenario, per DNA
G. rubens and G. texensis
summary
• Behavior/Morphology:
– Species divergent in male song and female preference
– Males not divergent in other traits, can form viable
hybrids
– Females divergent in ovipositor length
• Quantitative genetics:
– fast runaway co-evolution possible
• Molecular genetics:
– G. rubens evolved recently from within an isolated
subset of G. texensis
Current Work
Does reproductive isolation evolve proportional
to time (gradualist model of evolution) or
proportional to speciation events (punctuated
equilibrium model) and does it matter if the
taxa are allopatric or sympatric?
• Modest Goals:
– Describe speciation in Gryllus
– Describe song evolution in Gryllus
– See how they are related
• Problems:
– Most species of Gryllus in the western US and
Mexico undescribed
– Phylogenetic relationships unknown
Fieldwork: 2003- 2008
Camping:
• With Classes:
70 nights, 1150
student-nights
• 247 nights
total
G1 4 4 ru b e n
GrF 1 5 8
GrF 2 2 7
GrF 2 2 6
GrF 1 2 1
Gtd 6 8 6
Gtd 1 0 2
Gtd 1 0 4 2
G3 1 v e rn a l
G3 3 v e rn a l
G1 5 0 Gc h i r
G. rubens
G. texensis
G1 5 1 Gc h i r
G1 4 3 ru b e n
G1 3 7 ru b e n
G1 8 2 OEC AN
G1 0 1 Gc o h n
Grf1 5 1
GrF 2 5 1
GrF 2 4 8
GrF 2 1 1
GrF 2 1 0
GrF 1 6 9
GrF 1 6 8
‘oecanthus’
G. cohni
‘yucca’
GrF 1 2 2
Grd 4 3 7
Grd 4 0 5
Gtd 5 7
Gtd 6 7 9
Gtd 1 1 0 0
G1 6 5 y u c c a
G1 0 2 Gc o h n
‘sp. 2’
2 Gs p 2 T o n o
5 Gs p 2 T o n o
G5 6 GRe n o
G5 7 GRe n o
Gryllus
phylogenetics,
about 1500
sequences so
far
‘mojave’
G1 4 6 Gl a v a
2 8 9 Ch i ri c
3 1 1 Ch i ri c
2 0 D e e rC d r
2 2 D e e rC d r
2 3 D e e rC d r
2 1 D e e rC d r
19L am o ill
‘sp. 11’
7 Gs p 2 T o n o
6 Gs p 2 T o n o
4 Gs p 2 T o n o
G1 4 Gs p 2
‘sp. 13’
G8 G s p 2
G5 5 GRe n o
G1 8 m o j a v e
G1 7 m o j a v e
W G 1 7 Ap a c h
W G 1 6 Ap a c h
0 4 1 1 2 S ED
G1 4 7 Gl a v a
G. alogus
G8 4 Gs p 1 1
G5 4 Gs p 1 1
G5 3 Gs p 1 1
04 117m ad
0 4 2 b u rr o
G1 0 3 Gs p 1 3
G1 0 4 Gs p 1 3
G1 6 4 Gs p 1 3
G1 8 5 Gs p 1 3
G1 6 3 Gs p 1 3
1 7 4 G3 p 2 c 2
1 7 3 G3 p 3 c 2
‘sp. 10’
G. vocalis
307 alog us
G1 5 3 a l o g u
G1 5 2 a l o g u
‘california veletis’
W G1 0 v o c a l
0 4 9 0 Aft o
G9 8 Gs p 1 0
G9 7 Gs p 1 0
‘arizona stutter-triller’
G9 6 Gs p 1 0
G1 6 Gs p 1 0
G2 0 v o c a l i
G1 9 v o c a l i
G2 3 v o c a l i
G1 3 v o c a l i
W G1 2 v o c a l
W G1 1 v o c a l
0 4 9 2 Aft o
G1 5 4 i n te r
G. brevicaudus
G2 0 1 v e l e t
G5 0 v e l e ti
‘sp. 15’
G2 0 3 v e l e t
G1 1 v e l e ti
G1 2 v e l e ti
G9 v e l e ti s
G2 0 2 v e l e t
G1 0 v e l e ti
2 9 5 AAZ s tu
2 9 5 BAZ s tu
G. lineaticeps
2 9 4 AZ s t u t
G4 b re v i c a
W G 9 Ca rr i z
G6 b re v i c a
G5 b re v i c a
G1 1 9 Gc h i r
G. pennsylvanicus
0 4 4 Gs p 1 5
2 9 1 G6 p 3 c 8
‘grass’
2 9 3 Gs p 1 5
2 7 8 Gs p 1 5
3 0 5 Gs p 1 5
2 7 9 Gs p 1 5
G1 l i n e a t i
G8 9 l i n e a t
G2 2 l i n e a t
NCB Ip e n n s
UT M 3 p e n n
UT M 1 p e n n
G4 0 p e n n s y
G9 0 g ra s s
G9 5 g ra s s
G9 2 g ra s s
W G5 o v i s o p
W G 3 fi rm u s
G. ovisopis
G. firmus
G6 2 fi rm u s
G6 1 fi rm u s
W G 4 fi rm u s
G6 0 fi rm u s
‘insularis’
G1 1 8 Gtri l
G1 1 1 G3 p c
G1 2 2 g ry l l
G1 5 8 Gp e c o
‘roadside’
G1 5 9 Gp e c o
G1 5 5 i n te r
1 7 8 ro a d s i
G1 5 7 ro a d s
‘pecos’
G6 8 M tPa s s
G7 8 M tPa s s
G7 7 M tPa s s
G1 7 9 Gc h i r
G1 8 0 Gc h i r
2 9 B BCh i rp
3 0 B BCh i rp
2 5 D e e rC ri
G1 4 2 fa s tc
G3 0 v e l e ti
1 8 3 Gu a d a l
1 8 9 Gu a d a l
1 8 1 Gu a d a l
G6 3 c h i rp e
1 8 6 Gu a d a l
G2 6 v e rn a l
‘mtn. pass’
G. veletis
G2 7 v e rn a l
G3 8 fu l to n
G3 6 v e l e ti
W G 1 5 Ru b y M
W G 1 4 Ru b y M
W G 8 v e l e ti
W G1 3 v e l e t
G2 9 v e l e ti
G3 7 v e l e ti
G3 9 v e l e ti
G2 8 v e rn a l
0 4 4 4 p a rk
0 4 5 0 PA RK
0 4 4 7 PA RK
0 4 4 5 p a rk
04 118m ad
G3 2 fu l to n
‘guadalupe veletis’
G. vernalis
G. fultoni
‘parker cyn/Madera G.’
G3 4 fu l to n
G3 5 fu l to n
3 1 2 i n te g e
3 8 i n te g e r
2 8 i n te g e r
4 2 i n te g e r
‘rock’
4 1 i n te g e r
3 9 i n te g e r
G5 8 i n te g e
G5 9 i n te g e
G5 1 i n te g e
G7 2 i n te g e
G7 3 i n te g e
2 1 8 i n te g e
G9 1 i n te g e
G7 0 i n te g e
G. integer
2 8 1 i n te g e
2 1 1 i n te g e
‘integer’
1 7 5 i n te g e
1 6 9 i n te g e
1 7 2 i n te g e
1 7 1 i n te g e
2 3 3 i n te g e
‘integer’
2 1 4 i n te g e
G8 3 i n te g e
G8 6 i n te g e
04 108n ee
G1 2 6 Gb l k c
‘integer’
G1 2 7 Gb l k c
G1 9 9 h i l l s
G6 7 ro c k y
G1 6 2 Gb a g g
G6 9 G3 p c
G1 3 4 Gs p 2 9
‘rocky’
G1 6 1 Gs p 2 9
G2 0 0 h i l l s
G1 0 0 Gre d
G9 9 Gre d
G1 9 8 Gc h i r
G1 9 7 Gc h i r
3 2 6 p e rs o n
3 2 4 p e rs o n
‘baggeti’
3 2 1 p e rs o n
3 3 0 p e rs o n
G7 5 p e rs o n
3 2 5 p e rs o n
‘sp. 29’
3 2 8 p e rs o n
G7 6 p e rs o n
G1 9 4 s wa m p
G1 9 3 s wa m p
G8 8 a s s i m T
G1 0 9 s l o wc
G1 1 2 Gs p 1
G1 1 3 Gs p 1
G. personatus
G1 2 9 a s s i m
G4 7 a s s i m W
G4 6 a s s i m W
G8 2 a s s i m T
‘island’
G6 5 a s s i m T
G6 4 a s s i m T
G2 4 a s s i m E
G2 5 a s s i m E
W G1 a s s i m E
‘multipulsator’
W G2 a s s i m E
G2 a s s i m W
W G 6 Yu m a AZ
W G 7 Yu m a AZ
G3 a s s i m W
G2 1 a s s i m W
04 100o ax
G1 1 5 Gs p 1
W G2 2 b i m a c
W G2 3 b i m a c
1
G. assimilis
Example Tree
• Two Speciation
matrices
A
B
C
– One based on
genetic distance
– One based on #’s of
nodes (speciation
events)
D
E
F
G
H
I
J
Genetic Distance
Gallup Big Black Chirper
Utah “integer”
Arizona Stutter-triller
species 13
Multivariate Song Distance
Pulses per
burst
Frequency
Pulse Rate
Bursts per unit song
Song and Speciation
• Matrix of ‘song space’ distances
• Matrix of genetic distances
• Matrix of nodal distances
• Covariate matrix of Sympatry/Allopatry