Eunho Suh Biology of Wolbachia and Speciation Department of Entomology

Photo by Stphen L. Dobson ( u/index.php/Image:Dapi.gif) Wolbachia sp. in ovarium cells of Rhagoletis cerasi (cherry fruit fly). Photo by S. Bluemel (

Over 16 % of insects Coleoptera, Diptera, Hemiptera, Homoptera, Hymenoptera, Lepidoptera, Orthoptera 35 % of terrestrial isopods 6 of 16 species of spider mites and 4 of 7 species of predatory mites 9 of 10 species of filarial nematodes (R. Stouthamer et al ; JH Werren 1997) Distribution of Wolbachia

Taxonomy and Phylogeny Bacteria Proteobacteria  - subdivision Rickettsiales Rickettsiaceae Wolbachieae Wolbachia A & B groups : insects, mite, and crustaceans : 21 subgroups C & D groups : filarial nematodes E group : spring tail (Folsomia candida) F group : termites

Phylogenetic Tree of Wolbachia

(A. Jeyaprakash and M. A. Hoy 2000)

Phenotypic Effects on Hosts Cytoplasmic Incompatibility (CI) Parthenogenesis Inducing (PI) Feminization Male Killing Other Phenomena

Cytoplasmic Incompatibility (CI) Unidirectional CI

Genetic Variance of CI Wolbachia 4 strains - mod + res + : wild type - mod + res - : modification, no rescue - mod - res + : no modification, rescue - mod - res - : no cytoplasmic incompatibility

CI inducing mechanism of Wolbachia strains FM resc+mod+ resc+mod- offspring mod+ mod- resc- CI MF

Factors Influencing CI Density of Wolbachia : high density of Wolbachia => strong CI expression, high frequency of transmission Genotype of host : genotype specific Wolbachia strains => different CI expressions or other phenomena in different host genotypes Strains of Wolbachia : different Wolbachia strains => different CI expression in same host => bidirectional CI

Parthenogenesis Inducing (PI) Infected females produces infected females without fertilization Gamete duplication : no segregation in metaphase in first mitotic division => Diploid Haplodiploid specific (Hymenoptera spp.)

Feminization of Genetic Males Disruption of forming androgenic gland to develop to males Feminized males produces offspring Some isopod species and two Lepidopteran species (Ostrinia furnacalis, O. scapulalis)

Male Killing Secondary female biased sex ratios Wolbachia kills male progeny during embryogenesis Eliminating competition or providing resources to sibling females that feed dead brothers Two-spot lady bird(Aldalia bipunctata), African butterfly(Acraea encedon)

Speciation : CI Wolbachia Sperm competition : infected sperm shows fitness advantage Tribolium confusum Longevity : Wolbachia popcorn over-replicates in host tissues => host mortality Drosophila melanogaster Host fitness effects - Positive and Negative : filarial nematode produce no progeny without Wolbachia reduction in fecundity of Trichogramma deion, T. pretiosum Other Phenomena

Applications Biological Control Using CI Sterile male release => reduce reproductive potential of pest populations Bidirectionally incompatible Wolbachia strains => replace the existing population with less-harmful population of same species

Speciation by Wolbachia Infectious Speciation - M. J. Wade 2001, Nature

Evidence of Sepication by Wolbachia Wolbachia induced incompatibility precedes other hybrid incompatiblities in Nasonia - S. R. Bordenstein et al. 2001, Nature ;Bidrectional incompatibility Between Nasonia giraulti and N. longicornis No evidence of inviability and sterility among F1 hybrid females, and inviability and sterility of F2 hybrid males

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