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How many species are infected with Wolbachia?--A statistical analysis of current data.

Hilgenboecker K, Hammerstein P, Schlattmann P, Telschow A, Werren JH - FEMS Microbiol. Lett. (2008)

Bottom Line: Wolbachia are intracellular bacteria found in many species of arthropods and nematodes.Estimates suggest that at least 20% of all insect species are infected with Wolbachia.These estimates result from several Wolbachia screenings in which numerous species were tested for infection; however, tests were mostly performed on only one to two individuals per species.

View Article: PubMed Central - PubMed

Affiliation: Institute for Theoretical Biology, Humboldt University Berlin, Berlin, Germany. k.hilgenboecker@biologie.hu-berlin.de

ABSTRACT
Wolbachia are intracellular bacteria found in many species of arthropods and nematodes. They manipulate the reproduction of their arthropod hosts in various ways, may play a role in host speciation and have potential applications in biological pest control. Estimates suggest that at least 20% of all insect species are infected with Wolbachia. These estimates result from several Wolbachia screenings in which numerous species were tested for infection; however, tests were mostly performed on only one to two individuals per species. The actual percent of species infected will depend on the distribution of infection frequencies among species. We present a meta-analysis that estimates percentage of infected species based on data on the distribution of infection levels among species. We used a beta-binomial model that describes the distribution of infection frequencies of Wolbachia, shedding light on the overall infection rate as well as on the infection frequency within species. Our main findings are that (1) the proportion of Wolbachia-infected species is estimated to be 66%, and that (2) within species the infection frequency follows a 'most-or-few' infection pattern in a sense that the Wolbachia infection frequency within one species is typically either very high (>90%) or very low (<10%).

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Numbers of species with infection densities in the particular intervals. Gray bars describe the observations made in samples with sample size nj≥22. The black bars indicate the number of species expected based on B(iii). The value of the χ2- statistic is 8.4 (<14, error probability 5%), thus we can accept this distribution as an underlying density function. Here, also B(i) could be accepted, whereas B(ii) had to be rejected.
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fig02: Numbers of species with infection densities in the particular intervals. Gray bars describe the observations made in samples with sample size nj≥22. The black bars indicate the number of species expected based on B(iii). The value of the χ2- statistic is 8.4 (<14, error probability 5%), thus we can accept this distribution as an underlying density function. Here, also B(i) could be accepted, whereas B(ii) had to be rejected.

Mentions: All the resulting functions show a ‘most-or-few’ infection pattern, as very high as well as very low intraspecies infection frequencies are more likely to occur than infection frequencies in between (Figs 1 and 2). Thereby, it should be noted that a beta-distribution can take various forms. Also linear, unimodal or strictly increasing or decreasing functions are possible outcomes within the framework of a beta-binomial model. Further, the weighted average [Eqn. (1)] provides an estimate of the average infection frequency within a species, and an estimate of the overall infection rate is obtained by integrating the beta distributions [Eqn. (5)] from a threshold value c, above which species are considered to be infected, up to one (Table 3).


How many species are infected with Wolbachia?--A statistical analysis of current data.

Hilgenboecker K, Hammerstein P, Schlattmann P, Telschow A, Werren JH - FEMS Microbiol. Lett. (2008)

Numbers of species with infection densities in the particular intervals. Gray bars describe the observations made in samples with sample size nj≥22. The black bars indicate the number of species expected based on B(iii). The value of the χ2- statistic is 8.4 (<14, error probability 5%), thus we can accept this distribution as an underlying density function. Here, also B(i) could be accepted, whereas B(ii) had to be rejected.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2327208&req=5

fig02: Numbers of species with infection densities in the particular intervals. Gray bars describe the observations made in samples with sample size nj≥22. The black bars indicate the number of species expected based on B(iii). The value of the χ2- statistic is 8.4 (<14, error probability 5%), thus we can accept this distribution as an underlying density function. Here, also B(i) could be accepted, whereas B(ii) had to be rejected.
Mentions: All the resulting functions show a ‘most-or-few’ infection pattern, as very high as well as very low intraspecies infection frequencies are more likely to occur than infection frequencies in between (Figs 1 and 2). Thereby, it should be noted that a beta-distribution can take various forms. Also linear, unimodal or strictly increasing or decreasing functions are possible outcomes within the framework of a beta-binomial model. Further, the weighted average [Eqn. (1)] provides an estimate of the average infection frequency within a species, and an estimate of the overall infection rate is obtained by integrating the beta distributions [Eqn. (5)] from a threshold value c, above which species are considered to be infected, up to one (Table 3).

Bottom Line: Wolbachia are intracellular bacteria found in many species of arthropods and nematodes.Estimates suggest that at least 20% of all insect species are infected with Wolbachia.These estimates result from several Wolbachia screenings in which numerous species were tested for infection; however, tests were mostly performed on only one to two individuals per species.

View Article: PubMed Central - PubMed

Affiliation: Institute for Theoretical Biology, Humboldt University Berlin, Berlin, Germany. k.hilgenboecker@biologie.hu-berlin.de

ABSTRACT
Wolbachia are intracellular bacteria found in many species of arthropods and nematodes. They manipulate the reproduction of their arthropod hosts in various ways, may play a role in host speciation and have potential applications in biological pest control. Estimates suggest that at least 20% of all insect species are infected with Wolbachia. These estimates result from several Wolbachia screenings in which numerous species were tested for infection; however, tests were mostly performed on only one to two individuals per species. The actual percent of species infected will depend on the distribution of infection frequencies among species. We present a meta-analysis that estimates percentage of infected species based on data on the distribution of infection levels among species. We used a beta-binomial model that describes the distribution of infection frequencies of Wolbachia, shedding light on the overall infection rate as well as on the infection frequency within species. Our main findings are that (1) the proportion of Wolbachia-infected species is estimated to be 66%, and that (2) within species the infection frequency follows a 'most-or-few' infection pattern in a sense that the Wolbachia infection frequency within one species is typically either very high (>90%) or very low (<10%).

Show MeSH
Related in: MedlinePlus