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Biology of Wolbachia
and Speciation
Eunho Suh
Department of Entomology
Wolbachia sp. in ovarium cells of
Rhagoletis cerasi (cherry fruit fly).
Photo by S. Bluemel
(http://microbewiki.kenyon.edu/in
dex.php/Image:Wg1_image2.jpg)
Photo by Stphen L. Dobson
(http://microbewiki.kenyon.
edu/index.php/Image:Dapi.
gif)
Distribution of Wolbachia
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)
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
F
F
M
resc+
mod+
offspring
M
mod-
resc-
+
+
resc+
mod-
+
offspring
offspring
resc-
+
mod+
CI
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)
Other Phenomena
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
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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