Sexual selection and speciation: field crickets as a model system
David A. GrayCalifornia State University, Northridge
The Cricket Mating System
Cryptic sister species: Gryllus texensis and Gryllus rubens
Geographic Ranges
Male pulse rates (field matings, N = 451)
0
10
20
30
40
50
60
70
45 50 55 60 65 70 75 80 85 90 95
pulse rate @ 25 C
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
G. rubens (Fisher’s
Exact, P1-tailed < 0.000).
G. texensis (Fisher’s Exact, P1-tailed = 0.073)
Allo/Sym NS
0
10
20
30
40
50
60
70
80
90
100
Allopatry Sympatry
Percent Male Courtship
Conspecific female
Heterospecific female
0
10
20
30
40
50
60
70
80
90
100
Allopatry Sympatry
Percent Male Courtship
Conspecific female
Heterospecific female
G. rubens
G. texensis
Females
Species of Male:(Fisher’s Exact, G. rubens P1-tailed = 0.028, G. texensis P1-tailed = 0.000)
Courtship song played: (Fisher’s Exact, G. rubens P1-tailed = 0.000, G. texensis P1-tailed = 0.000)
Allo/Sym NS
0
20
40
60
80
100
G. rubens male G. texensis male G. rubens male G. texensis male
G. rubens song G. rubens song G. texensis song G. texensis song
% females mounting
AllopatrySympatry
0
20
40
60
80
100
G. rubens male G. texensis male G. rubens male G. texensis male
G. rubens song G. rubens song G. texensis song G. texensis song
Male Song and Species Combination
% females mounting
AllopatrySympatry
G. rubens females
G. texensis females
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. texensis164 haplotypes (N = 188)
• G. rubens27 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
Gryllus phylogenetics,
about 1500 sequences so
far
1
G144rubenGrF158GrF227
GrF226GrF121Gtd686Gtd102
Gtd1042G31vernalG33vernalG150Gchir
G151GchirG143rubenG137ruben
G182OECANG101GcohnGrf151
GrF251GrF248
GrF211GrF210GrF169GrF168GrF122Grd437Grd405Gtd57
Gtd679Gtd1100
G165yuccaG102Gcohn2Gsp2Tono5Gsp2Tono
G56GRenoG57GReno
G146Glava289Chiric311Chiric20DeerCdr22DeerCdr23DeerCdr21DeerCdr19Lamoill7Gsp2Tono6Gsp2Tono4Gsp2TonoG14Gsp2G8Gsp2G55GRenoG18mojaveG17mojaveWG17ApachWG16Apach
04 112SEDG147GlavaG84Gsp11
G54Gsp11G53Gsp11
04 117mad04 2burro
G103Gsp13G104Gsp13G164Gsp13G185Gsp13G163Gsp13
174G3p2c2173G3p3c2
307alogusG153aloguG152alogu
WG10vocal04 90AftoG98Gsp10G97Gsp10G96Gsp10
G16Gsp10G20vocali
G19vocaliG23vocaliG13vocaliWG12vocal
WG11vocal04 92Afto
G154interG201velet
G50veletiG203velet
G11veletiG12veleti
G9veletisG202veletG10veleti
295AAZstu295BAZstu
294AZstutG4brevicaWG9CarrizG6brevicaG5brevica
G119Gchir04 4Gsp15291G6p3c8
293Gsp15278Gsp15305Gsp15
279Gsp15G1lineati
G89lineatG22lineat
NCBIpennsUTM3pennUTM1pennG40pennsy
G90grassG95grassG92grass
WG5ovisopWG3firmusG62firmusG61firmusWG4firmus
G60firmusG118Gtril
G111G3pcG122gryll
G158GpecoG159Gpeco
G155inter178roadsiG157roads
G68MtPassG78MtPassG77MtPassG179GchirG180Gchir29BBChirp
30BBChirp25DeerCri
G142fastcG30veleti
183Guadal189Guadal181GuadalG63chirpe
186GuadalG26vernalG27vernal
G38fultonG36veletiWG15RubyMWG14RubyMWG8veletiWG13veletG29veletiG37veletiG39veleti
G28vernal04 44park04 50PARK04 47PARK04 45park
04 118madG32fultonG34fultonG35fulton
312intege38integer28integer42integer41integer39integer
G58integeG59intege
G51integeG72integeG73intege
218integeG91integeG70intege
281intege211intege175intege
169intege172intege171intege
233intege214integeG83intege
G86intege04 108neeG126GblkcG127GblkcG199hills
G67rockyG162Gbagg
G69G3pcG134Gsp29
G161Gsp29G200hills
G100GredG99Gred
G198GchirG197Gchir
326person324person
321person330person
G75person325person
328personG76personG194swampG193swamp
G88assimTG109slowcG112Gsp1G113Gsp1G129assimG47assimWG46assimWG82assimTG65assimT
G64assimTG24assimEG25assimE
WG1assimEWG2assimE
G2assimWWG6YumaAZWG7YumaAZG3assimW
G21assimW04 100oax
G115Gsp1WG22bimac
WG23bimac
G. rubens
G. texensis
‘oecanthus’
G. cohni
‘yucca’
‘sp. 2’
‘mojave’
‘sp. 11’
‘sp. 13’
G. alogus
‘sp. 10’
G. vocalis
‘california veletis’
‘arizona stutter-triller’
G. brevicaudus
‘sp. 15’
G. lineaticeps
G. pennsylvanicus
‘grass’
G. ovisopis
G. firmus
‘insularis’
‘roadside’
‘pecos’
‘mtn. pass’
G. veletis
‘guadalupe veletis’
G. vernalis
G. fultoni
‘parker cyn/Madera G.’
‘rock’
G. integer
‘integer’
‘integer’
‘integer’
‘rocky’
‘baggeti’
‘sp. 29’
G. personatus
‘island’
‘multipulsator’
G. assimilis
Example Tree
• Two Speciation matrices– One based on
genetic distance– One based on #’s of
nodes (speciation events)
Genetic Distance
ABC
DE
FG
HI
J
species 13
Utah “integer”
Gallup Big Black Chirper
Arizona Stutter-triller
Multivariate Song Distance
Pulse Rate
Pulses per burst Frequency
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