College of Natural & Agricultural Sciences

Richard Stouthamer

Richard Stouthamer

Professor of Entomology

BSc Environmental Sciences 1977

Wageningen University, The Netherlands

BSc Biology 1980

Wageningen University, The Netherlands

MSc Biology 1983

Wageningen University, The Netherlands

PhD Entomology 1989

University of California, Riverside

Research Areas

Molecular Population Genetics

Contact Information
Entomology Bldg. 383
(951) 827-2422

The research in my lab concentrates on two topics: 1. symbionts and sex ratio distortion in insects, 2. the use of molecular techniques to study population genetics, identification of cryptic species, biotypes and their origin. Symbionts and sex ratio distortion   In many wasps species infections with symbiotic bacteria cause female biased sex ratios. Wolbachia bacteria induce parthenogenesis in their hosts and consequently infected wasps produce exclusively female progeny. We study the relationship between the Wolbachia and its host, mainly in wasps of the genus Trichogramma. We are doing a large field study in the Mojave Desert trying to understand the dynamics of the Wolbachia infection in the population of Trichogramma kaykai. In addition to studying fundamental aspects of this symbiosis, we also study applied aspects of the parthenogenesis Wolbachia. For biological control the use of parthenogenetic forms of wasp species can be considered an advantage because only female wasps kill pest insects by laying their eggs in or on the pest insect. We also study another sex ratio distorter; one that causes fertilized eggs destined to be females to develop into males. This Paternal Sex Ratio (PSR) chromosome is an extremely selfish genetic element that propagates itself by destroying all the wasp chromosomes it contacts. We are trying to understand the mechanism of the chromosome destruction. In addition to these fundamental questions we are also considering if the PSR chromosome can be used in population control of insects such as thrips, sawflies, ants etc. Molecular techniques for population studies We apply various molecular techniques such as microsatellites, AFLP, RAPD etc. in population studies. These methods are used to determine mating structure of populations (important for the dynamics of sex ratio distorters), the origin of introduced species, gene flow between populations and to simplify identification of cryptic species.  

Awards Received

2007 - Elected Fellow, American Association for the Advancement of Science


Hoddle, M.S., L. A. Mound, P. F. Rugman-Jones, and R. Stouthamer 2008. Synonomy of Five Scirtothrips species (Thysanoptera: Thripidae) Described from Avocados (Persea americana) in Mexico. Florida Entomologist 91:16-21 

Hoddle, M.S., J. M. Heraty, P. F. Rugman-Jones, L. A. Mound, and R. Stouthamer 2008. Relationships Among Species of Scirtothrips Shull 1909 (Thysanoptera: Thripidae, Thripinae) Using Molecular and Morphological Data Ann. Entomol. Soc. Am. 101(3): 491-500 

Adachi-Hagimori, T., K. Miura, and R. Stouthamer. 2008. New cytogenetic mechanism for bacterial endosymbiont-induced parthenogenesis in Hymenoptera. Proceedings Royal Society 275:2667-2673 

Hansen, A.K., J.T. Trumble, R. Stouthamer, T.D. Paine. 2008. New Huanglongbing (HLB) Candidatus species, “C. Liberibacter psyllaurous”, found to infect tomato and potato is vectored by the psyllid Bactericerca cockerelli (Sulc). Applied and Environmetal Microbiology 74:5862-5865. 

Gols, R., C. Schutte, R. Stouthamer, and M. Dicke. 2007. PCR-based identification of the pathogenic bacterium, Acaricomes phytoseiuli, in the biological control agent Phytoseiulus persimilis (Acari: Phytoseiidae). Biological Control 42:316-325 

Hansen, A. K., G. Jeong, T. D. Paine, and R. Stouthamer 2007. Frequency of Secondary Symbiont Infection in an Invasive Psyllid Relates to Parasitism Pressure on a Geographic Scale in California. Applied and Environmetal Microbiology 73: 7531–7535 

P. F. Rugman-Jones, M. S. Hoddle, R. Stouthamer. (2007) Population genetics of Scirtothrips perseae: tracing the origin of a recently introduced exotic pest of Californian avocado orchards, using mitochondrial and microsatellite DNA markers. Entomologia Experimentalis et Applicata (accepted) 

Gavotte, L., Henri, H., Stouthamer, R., Charif, D., Charlat, S., Boulétreau, M. and Vavre, F. (2007). A survey of the bacteriophage WO in the endosymbiotic bacteria Wolbachia. Molecular Biology and Evolution 24:427-435. 

Liu, D., J. T. Trumble and R. Stouthamer. (2006). Molecular characterization indicates recent introductions of tomato psyllid (Bactericera cockerelli) into western North America are genetically different from eastern populations. Entomologia Experimentalis et Applicata 118:177-183. 

Rugman-Jones, P. F. , M. S. Hoddle, L.A. Mound, R. Stouthamer. (2006). Molecular identification key for the pest species of Scirtothirps (Thysanoptera: Thripidae). Journal of Economic Entomology 99:1813-1819. 

Jeong, G. & Stouthamer, R. (2006). No effect of postzygotic reproductive isolation on the interspecific transmission of the paternal sex ratio (PSR) chromosome in Trichogramma. Entomologia Experimentalis et Applicata 120: 33-40. 

Jeong, G. & R. Stouthamer. (2005). Genetics of female functional virginity in the parthenogenesis-Wolbachia infected parasitoid wasp Telenomus nawai (Hymenoptera: Scelionidae). Heredity 92: 402-407. 

Schuenzel, E.L., M. Scally, R. Stouthamer, and L. Nunney. (2005). A multigene phylogentic study of clonal diversity and divergence in North American strains of the plant pathogen Xylella fastidiosa. Applied and Environmental Microbiology 71:3832-3839. 

Rugman-Jones, P. F., A.R. Weeks, M. S. Hoddle, R. Stouthamer. (2005). Isolation and characterization of microsatellite loci in the avocado thrips Scirtothrips perseae(Thysanoptera: Thripidae). Molecular Ecology Notes 5:644-646. 

Scally, M., E. L. Schuenzel, R.Stouthamer, and L. Nunney (2005). A Multilocus Sequence Type System for the plant pathogen Xylella fastidiosa and the relative contribution of recombination versus point mutation to clonal diversity. Applied and Environmental Microbiology 71: 8491-8499 

van Vugt, J.F.A., S. de Nooijer, Jong and R. Stouthamer. (2005). Characterization of repeat sequences on the genome of the parasitic wasp Trichogramma kaykai and its paternal sex ratio chromosome. Chromosoma 114: 410-419. 

Vavre, F., J. H. de Jong, and R. Stouthamer. 2004. Cytogenetic mechanism and genetic consequences of thelytoky in the wasp Trichogramma cacoeciae. Heredity 93: 592-596 . 

Vickerman D. B., M. S. Hoddle, S. Triapitsyn and R. Stouthamer. 2004. Species identity of geographically distinct populations of the glassy-winged sharpshooter parasitoid Gonatocerus ashmeadi: Morphology, DNA sequences and reproductive compatibility. Biological Control 31:338-345 

Niyibigira, E.I., W. A. Overholt & R. Stouthamer. 2004. Cotesia flavipes Cameron and Cotesia sesamiae (Cameron) (Hymenoptera: Braconidae) do not exhibit Complementary Sex Determination: Evidence from field populations. Applied Entomology and Zoology 39: 705-715. 

Niyibigira, E.I., W. A. Overholt & R. Stouthamer. 2004. Cotesia flavipes Cameron (Hymenoptera: Braconidae) does not exhibit Complementary Sex Determination (ii) Evidence from laboratory experiments. Applied Entomology and Zoology 39: 717-725. 

Gavotte, L., F. Vavre, H.M. Ravallec, R. Stouthamer and M. Bouletreau. 2004. Diversity, distribution and specificity of WO phage infection in Wolbachia of four insect species. Insect Molecular Biology. 13: 147-153. 

Weeks, A.R. and R. Stouthamer. 2004. Increased fecundity associated with infection by a Cytophaga-like intracellular bacterium in the predatory mite, Metaseiulus occidentalis. Proceedings of the Royal Society London B 271 (Suppl. 4): S193-S195. 

Huigens, M.E., R.P. de Almeida, P. Boons, R.F. Luck and R. Stouthamer. 2004. Natural interspecific and intraspecific horizontal transfer of parthenogensis-inducing Wolbachi in Trichogramma wasps. Proceedings of the Royal Society London B 271: 509-515. 

Huigens, M.E., C.L. Hohmann, R.F. Luck, G. Gort and R. Stouthamer. 2004. Reduced competitive ability due to Wolbachia infection in the parasitoid wasp Trichogramma kaykai. Entomologia Experimentalis et Applicata. 110: 115-123. 

Pinto, J.D., G.R. Plantner and R. Stouthamer. 2003. The systematics of the Trichogramma minutum species complex (Hymenoptera: Trichogrammatidae), a group of important North American biological control agents: The evidence from reproductive compatibility and allozymes. Biological Control 27: 167-180 

van Vugt, J.F.A., M. Salverda, J.H. de Jong and R. Stouthamer. 2003. The paternal sex ratio chromosome in the parasitic wasp Trichogramma kaykai condenses the paternal chromosomes into a dense chromatin mass. Genome 46: 580-587.

Weeks, A.R., R. Velten and R. Stouthamer. 2003. Incidence of a new sex-ratio distorting endosymbiotic bacterium among arthropods. Proc. Royal Soc. London (B) 270: 1857-1865.

De Almeida, R.A. and R. Stouthamer. 2003. Molecular identification of Trichogramma cacoeciae Marchal (Hymenoptera: Trichogrammatidae): A new record for Peru. Neotropical Entomology. 32: 269-272. 

Borghuis, A., J.D. Pinto, G.R. Platner and R. Stouthamer. 2003. Partial cytochrome oxidase II sequences distinguish the sibling species Trichogramma minutum Riley and Trichogramma platneri Nagarkatti. Biological Control 30: 90-94. 

Pinto, J.D., A.B. Koopmanschap, G.R. Platner and R. Stouthamer. 2002. The North American Trichogramma (Hymenoptera: Trichogrammatidae) parasitizing certain Tortricidae (Lepidoptera) on apple and pear, with ITS2 DNA characterizations and description of a new species. Biological Control 23: 134-142 

Mochiah, M.B., A.J. Ngi-Song, W.A. Overholt and R. Stouthamer. 2002. Wolbachiainfection in Cotesia sesamiae (Hymenoptera: Braconidae) causes cytoplasmic incompatibility: implications for biological control. Biological Control 25: 74-80. 

Stouthamer, R and F. Mak. 2002. Influence of antibiotics on the offspring production of the Wolbachia-infected parthenogenetic parasitoid Encarsia formosa. Journ. Invert. Path. 80: 41-45 

Tagami, Y., K. Miura, and R. Stouthamer. 2002. Positive effect of fertilization on the survival rate of immature stages in a Wolbachia-associated thelytokous line of Trichogramma deionand T. kaykai. Entom. Exp. et App. 105: 165-167 

Mochiah, M.B., A.J. Ngi-Song, W.A. Overholt and R. Stouthamer. 2002. Variation in encapsulation sensitivity of Cotesia sesamiae biotypes to Busseola fusca. Entom. Exp. et App. 105: 111-118 

Stouthamer, R., van Tilborg M., de Jong, H., Nunney, L. & Luck, R.F. (2001). Selfish element maintains sex in natural populations of a parasitoid wasp. Proc. Royal Soc. London 268: 617-622. 

Stouthamer, R., Jochemsen, P., Platner, G.R. & Pinto. J.D. (2000). Crossing incompatibility between Trichogramma minutum and T. platneri and its implications for their application in biological control. Env. Ent. 29: 827-837. 

Huigens, M. E., R. F. Luck, R.G.H. Klaassen, F.M.P.M. Maas, M.J.T.N. Timmermans, and R. Stouthamer. 2000. Infectious parthenogenesis. Nature 405:178-179. 

Stouthamer, R., P. Jochemsen, G. R. Platner, and J. D. Pinto. 2000. Crossing incompatibility between Trichogramma minutum and T. platneri and its implications for their application in biological control. Environmental Entomology. 29(4): 832-837. 

Stouthamer R., Y. Gai, A.B. Koopmanschap, J. D. Pinto, and G.R. Platner. 2000. ITS-2 sequences do not differ for the closely related species Trichogramma minutum and T. platneri. Entomologia Experimentalis et Applicata 95:105-111. 

Silva, I.M.M.S., M.M.M. van Meer, M. M. Roskam, A. Hoogenboom, G. Gort, and R. Stouthamer. 2000. Biological control potential of Wolbachia infected (unisexual) versus uninfected (sexual) wasps: laboratory and greenhouse evaluation of Trichogramma cordubensis and T. deion strains. BioControl 10: 223-238. 

Stouthamer, R., Jochemsen, P., Platner, G.R. & Pinto. J.D. (2000). Crossing incompatibility between Trichogramma minutum and T. platneri and its implications for their application in biological control. Env. Ent. 29: 827-837. 

Hurst, G.D.D., J. H. Graf von der Schulenburg, T.M.O. Majerus, D. Bertrand, I. A. Zakharov, J. Baungaard, W. Vokl, R. Stouthamer, and M.E.N. Majerus. 1999. Invasion of one insect species, Adalia bipunctata, by two different male-killing bacteria. Insect Molecular Biology 8:133-139. 

van Meer, M.M.M. and R. Stouthamer. 1999. Cross-order transfer of Wolbachia from Muscidifurax uniraptor (Hymenoptera: Pteromalidae) to Drosophila simulans (Diptera: Drosophilidae). Heredity 82:163-169. 

van Meer, M.M.M., F.J.P.M. van Kan, and R. Stouthamer. 1999. Spacer 2 region and 5S rDNA variation of Wolbachia strains involved in cytoplasmic incompatibility or sex-ratio distortion in arthropods. Letters in Applied Microbiology 28:17-22. 

Hurst, G.D.D., F. M. Jiggins, J.H.G. Von Schulenburg, D. Bertrand, S. A. West, I. Goriacheva, I. A. Zakharov, J. H. Werren, R. Stouthamer, and M.E.N. Majerus. 1999. Male-killing Wolbachia in two species of insect. Proc. R. Soc. Lond. B 266: 735-740. 

van Meer M.M.M., J. Witteveldt, and R. Stouthamer. 1999. Phylogeny of the arthropod endosymbiont Wolbachia, based on the WSP gene. Insect Molecular Biology 8:399-408. 

Stouthamer, R., H. Jianguo, F.J.P.M. van Kan, G. R. Platner, and J. D. Pinto. 1999. The utility of internally transcribed spacer 2 DNA sequences of the nuclear ribosomal gene for distinguishing sibling species of Trichogramma. BioControl 43:421-440. 

Honda, J., I.M.M.S. Silva, J. Vereijssen, and R. Stouthamer. 1999. Laboratory bioassay and greenhouse evaluation of Trichogramma cordubensis strains from Portugal. BioControl 44:1-11. 

Silva, I.M.M.S. and R. Stouthamer. 1999. Do sympatric Trichogramma species parasitize the pest insect Helicoverpa armigera and the beneficial insect Chrysoperla carnea in different proportions? Entomologia Experimentalis et Applicata 92:101-107. 

Silva, I.M.M.S., J. Honda, F.J.P.M. van Kan, J. Hu, L. Neto, B. Pintureau, and R. Stouthamer. 1999. Molecular differentiation of five Trichogramma species occurring in Portugal. Biological Control 16:177-184. 

van Meer, M.M.M., J. Witteveldt, and R. Stouthamer. 1999. Development of a micro-injection protocol for the parasitoid Nasonia vitripennis. Entomologia Experientalis et Applicata 93:325-329. 

Schilthuizen, M., G. Nordlander, R. Stouthamer, and J.J.M. van Alphen. 1998. Morphological and molecular phylogenetics in the genus Leptopilina (Hymenoptera: Cynipoidea: Eucoilidae). Systematic Entomology. 23:253-264. 

Schilthuizen, M., J. Honda, and R. Stouthamer. 1998. Parthenogenesis-inducing Wolbachia in Trichogramma kaykai (Hymenoptera: Trichogrammatidae) originates from a single infection. Ann. Entomol. Soc. Am. 91:410-414. 

Schilthuizen, M. and R. Stouthamer. 1998. Distribution of Wolbachia among the guild associated with the parthenogenetic gall wasp Diplolepis rosae. Heredity 81:270-274. 

Schoenmaker, A., F. van den Bosch, and R. Stouthamer. 1998. Symbiontic bacteria in parasitoid populations: coexistence of Wolbachia-infected and uninfected Trichogramma. Oikos 81:587-597 

Riparbelli, M. G., R. Stouthamer, R. Dallai, and G. Callaini. 1998. Microtubule organization during the early development of the parthenogenetic egg of the hymenopteran Muscidifurax uniraptor. Developmental Biology 195:89-99. 

Ngi-Song, A. J., W. A. Overholt, and R. Stouthamer. 1998. Suitability of Busseola fuscaand Sesamia calamistis (Lepidoptera: Noctuidae) for the development of two populations of Cotesia sesamiae in Kenya. Biological Control 12:206-214. 

Pinto, J. D., R. Stouthamer, and G. R. Platner. 1997. A new cryptic species of Trichogramma (Hymenoptera: Trichogrammatidae) from the Mojave desert of California as determined by morphological, reproductive and molecular data. Proc. Entomol. Soc. Wash. 99:238-247. 

Schilthuizen, M. and R. Stouthamer. 1997. Horizontal transmission of parthenogenesis-inducing microbes in Trichogramma wasps. Proc. R. Soc. Lond. (B) 264,361-366. 

Stouthamer R., R. F. Luck, G. R. Platner, J. D. Pinto, and B. Stephens. 1996. Non-reciprocal cross-incompatibility in Trichogramma deion. Ent. exp. appl. 80:481-489. 

Werren J. H., G.D.D. Hurst, W. Zhang, J.A.J. Breeuwer, R. Stouthamer, and M.E.N. Majerus. 1994. Rickettsial relative associated with male killing in the ladybird beetle (Adalia bipunctata). J. Bacteriol. 176:388-394. 

Stouthamer, R. and J. D. Kazmer. 1994. Cytogenetics of microbe-associated parthenogenesis and its consequences for gene flow in Trichogramma wasps. Heredity 73:317-327. 

Stouthamer R., J.A.J. Breeuwer, R. F. Luck, and J. H. Werren. 1993. Molecular identification of microorganisms associated with parthenogenesis. Nature 361:66-68. 

Stouthamer R. and J. H. Werren. 1993. Microbes associated with parthenogenesis in wasps of the genus Trichogramma. J. Invert. Pathol. 61:6-9. 

Stouthamer R. and R. F. Luck. 1993. Influence of microbe-associated parthenogenesis on the fecundity in Trichogramma deion and T. pretiosum. Entomol. exp. appl. 67:183-192. 

Stouthamer R. 1993. The use of sexual versus asexual wasps in biological control. Entomophaga 38:3-6. 

Stouthamer R., R.F. Luck, and J. H. Werren. 1992. Genetics of sex determination and the improvement of biological control using parasitoids. Environ. Entomol. 21:427-435. 

Breeuwer J.A.J., R. Stouthamer, W. G. Weisburg, and J. H. Werren. 1992. Phylogeny of cytoplasmic incompatibility micro-organisms in the parasitoid wasp genus Nasonia(HymenopteraPteromalidae) based on 16s ribosomal DNA sequences. Insect Molecular Biology 1:25-36. 

Stouthamer R. and R. F. Luck. 1991. Transition from bisexual to unisexual cultures in Encarsia perniciosi Tower (Hymenoptera; Aphelinidae): New data and a reinterpretation. Ann. Entomol. Soc. Am. 84:150-157. 

Pinto J. D, R. Stouthamer, G. R. Platner, and E. R. Oatman. 1991. Variation in reproductive compatibility in Trichogramma and its taxonomic significance. (Hymenoptera: Trichogrammatidae). Ann. Entomol. Soc. Am. 84:37-46. 

Stouthamer R., J. D. Pinto, G. R. Platner, and R. F. Luck. 1990. Taxonomic status of thelytokous forms of Trichogramma (Hymenoptera; Trichogrammatidae). Ann. Entomol. Soc. Am. 83:475-481. 

Stouthamer, R., R. F. Luck, and W. D. Hamilton. 1990. Antibiotics cause parthenogenetic Trichogramma (Hymenoptera/Trichogrammatidae) to revert to sex. Proc. Natl. Acad. Sci. 87:2424-2427.

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