Sexual selection and speciation: field crickets as a model system

1. Sexual selection and speciation: field crickets as a model system David A. Gray California State University, Northridge

5. The Cricket Mating System

6. Cryptic sister species: Gryllus texensis and Gryllus rubens

7. Geographic Ranges

8. Male pulse rates (field matings, N = 451)

9. Lab hybrid songs

11. 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.

13. Courtship as a pre-mating isolating mechanism? • Geographic variation in courtship • Sound and Smell • Muted males • Song playback

14. 568 trials completed……

15. Males G. rubens G. rubens(Fisher’s Exact, P1-tailed < 0.000). G. texensis(Fisher’s Exact, P1-tailed= 0.073) Allo/Sym NS G. texensis

16. G. rubens females G. texensis females Females Species of Male:(Fisher’s Exact, G. rubensP1-tailed = 0.028, G. texensisP1-tailed = 0.000) Courtship song played: (Fisher’s Exact, G. rubensP1-tailed = 0.000, G. texensisP1-tailed = 0.000) Allo/Sym NS

17. 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)

18. G. texensis • 164 haplotypes (N = 188) • G. rubens • 27 haplotypes (N = 177) • AMOVA • Between species 10.22% • P < 0.0001

19. 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)

20. Geographic scenario, per DNA

21. 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

22. 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?

23. 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

24. Fieldwork: 2003- 2008 • Camping: • With Classes: 70 nights, 1150 student-nights • 247 nights total

25. 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 Gryllus phylogenetics, about 1500 sequences so far

26. A B C D E F G H I J Genetic Distance Example Tree • Two Speciation matrices • One based on genetic distance • One based on #’s of nodes (speciation events)

27. Gallup Big Black Chirper Utah “integer” Arizona Stutter-triller species 13

28. Pulses per burst Frequency Pulse Rate Bursts per unit song Multivariate Song Distance

29. Song and Speciation • Matrix of ‘song space’ distances • Matrix of genetic distances • Matrix of nodal distances • Covariate matrix of Sympatry/Allopatry