Eunho Suh

Biology ofBiology of Wolbachia Wolbachia and Speciationand Speciation

Department of Entomology

Photo by Stphen L. Dobson(http://microbewiki.kenyon.edu/index.php/Image:Dapi.gif)

Wolbachia sp. in ovarium cells of Rhagoletis cerasi (cherry fruit fly). Photo by S. Bluemel (http://microbewiki.kenyon.edu/index.php/Image:Wg1_image2.jpg)

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. 1999 ; JH Werren 1997)

Distribution of Wolbachia

Taxonomy and Phylogeny

Bacteria Proteobacteria - subdivisionRickettsialesRickettsiaceae 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)FeminizationMale KillingOther 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 CI inducing mechanism of WolbachiaWolbachia strains strains

F M

resc+ mod+

resc+ mod-

offspring offspring

offspring

+

+

+

+

mod+

mod-

resc-

resc-

CI

M F

Factors Influencing CIDensity 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 femaleswithout 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 todevelop 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 WolbachiaInfectious Speciation- M. J. Wade 2001, Nature

Evidence of Sepication by WolbachiaWolbachia induced incompatibility precedes other hybrid incompatiblities in Nasonia- S. R. Bordenstein et al. 2001, Nature

;Bidrectional incompatibilityBetween 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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