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)

Lab hybrid songs

Quantitative genetics: G. texensis ‘Meta-population’ heritability –Male song h 2 = * –Female preference h 2 = * Genetic correlation –r G = * * 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, P 1-tailed < 0.000). G. texensis (Fisher’s Exact, P 1-tailed = 0.073) Allo/Sym NS G. rubens G. texensis

Females Species of Male :(Fisher’s Exact, G. rubens P 1-tailed = 0.028, G. texensis P 1-tailed = 0.000) Courtship song played: (Fisher’s Exact, G. rubens P 1-tailed = 0.000, G. texensis P 1-tailed = 0.000) Allo/Sym NS 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. texensis 164 haplotypes (N = 188) G. rubens 27 haplotypes (N = 177) AMOVA Between species 10.22% P <

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: Camping: With Classes: 70 nights, 1150 student-nights 247 nights total

Gryllus phylogenetics, about 1500 sequences so far 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’ ‘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 ABCDEFGHIJABCDEFGHIJ

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