Abstract
The 37 currently recognized Bemisia tabaci cryptic species are economically important species and contain both primary and secondary endosymbionts, but their diversity has never been mapped systematically across the group. To achieve this, PacBio sequencing of full-length bacterial 16S rRNA gene amplicons was carried out on 21 globally collected species in the B. tabaci complex, and two samples from B. afer were used here as outgroups. The microbial diversity was first explored across the major lineages of the whole group and 15 new putative bacterial sequences were observed. Extensive comparison of our results with previous endosymbiont diversity surveys which used PCR or multiplex 454 pyrosequencing platforms showed that the bacterial diversity was underestimated. To validate these new putative bacteria, one of them (Halomonas) was first confirmed to be present in MED B. tabaci using Hiseq2500 and FISH technologies. These results confirmed PacBio is a reliable and informative venue to reveal the bacterial diversity of insects. In addition, many new secondary endosymbiotic strains of Rickettsia and Arsenophonus were found, increasing the known diversity in these groups. For the previously described primary endosymbionts, one Portiera Operational Taxonomic Units (OTU) was shared by all B. tabaci species. The congruence of the B. tabaci-host and Portiera phylogenetic trees provides strong support for the hypothesis that primary endosymbionts co-speciated with their hosts. Likewise, a comparison of bacterial alpha diversities, Principal Coordinate Analysis, indistinct endosymbiotic communities harbored by different species and the co-divergence analyses suggest a lack of association between overall microbial diversity with cryptic species, further indicate that the secondary endosymbiont-mediated speciation is unlikely to have occurred in the B. tabaci species group.
Highlights
The 37 currently recognized Bemisia tabaci cryptic species are economically important species and contain both primary and secondary endosymbionts, but their diversity has never been mapped systematically across the group
A comparison of bacterial alpha diversities, Principal Coordinate Analysis, indistinct endosymbiotic communities harbored by different species and the co-divergence analyses suggest a lack of association between overall microbial diversity with cryptic species, further indicate that the secondary endosymbiont-mediated speciation is unlikely to have occurred in the B. tabaci species group
The alpha diversities for bacterial Operational Taxonomic Units (OTU) from different cryptic species ranged from 0.21–1.59 Shannon index and 0.27–0.97 Simpson index, which are low (Table 2) yet similar to the result obtained by Jing, et al.[30]
Summary
The 37 currently recognized Bemisia tabaci cryptic species are economically important species and contain both primary and secondary endosymbionts, but their diversity has never been mapped systematically across the group. Extensive comparison of our results with previous endosymbiont diversity surveys which used PCR or multiplex 454 pyrosequencing platforms showed that the bacterial diversity was underestimated To validate these new putative bacteria, one of them (Halomonas) was first confirmed to be present in MED B. tabaci using Hiseq2500 and FISH technologies. Many studies have surveyed the S-endosymbionts using 16S ribosomal RNA (rRNA) molecular markers by normal PCR in field-collected whiteflies[16,17,18] and showed that the infection incidences of different S-endosymbionts differ Most of these studies are mainly focused on the diversity of endosymbionts in B. tabaci with restricted region distributions and lack an angle of linking these diversities with its hosts. We chose the PacBio sequencing instrumentation for the first time to systematically study the endosymbionts diversity of B. tabaci cryptic species
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