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