Weevil-associated bacterial diversity.

<p>Histogram representing the taxonomic assignment of bacterial 16S rRNA gene sequences associated with the analyzed weevils; A: phylum level, B: family level.</p

Diversity indices estimated for the bacterial communities associated with the analyzed <i>Rhynchophorus</i> specimens.

<p>^a The mean and standard deviation of the estimated diversity indices are reported for each analyzed group of weevils;</p><p>^b Number of sequences obtained for each specimens after chimeric and contaminants removal.</p><p>Diversity indices estimated for the bacterial communities associated with the analyzed <i>Rhynchophorus</i> specimens.</p

Genera of bacteria identified in the weevil microbiotas with their relative average abundance expressed as percentage.

<p>In this table are reported the bacterial genera present with abundance > 1% in at least one specimens. The main differences in the bacterial genera associated with apple and palm are highlighted in bold.</p><p>^a The gender of the specimens is reported; <i>f</i>: female, <i>m</i>: male.</p><p>Genera of bacteria identified in the weevil microbiotas with their relative average abundance expressed as percentage.</p

Operational taxonomic units shared by the three groups of weevils.

<p>Venn diagram showing the shared bacterial OTUs (at 97% similarity) between all studied weevils groups.</p

Palm-associated bacterial diversity.

<p>Pie charts representing the taxonomic assignment of bacterial 16S rRNA gene sequences associated with the analyzed the palm tissues; A: phylum level, B: family level.</p

Relative abundance of the strains isolated from the different organs of RPW.

<p>A: histogram representing the relative abundance of strains at order level isolated by different organs; B: pie chart representing the cumulative abundance of the different strains at the genus level.</p

Bacterial communities and ecological factors.

<p>Biplot of the first 2 axes for the Non-Metric Multi-Dimensional Scaling representing correlations between the OTUs Chao dissimilarity index and ecological factors (i.e. diet and temperature). The black squares, the black and open circles represent respectively: RPW_PALM, <i>R</i>. <i>vulneratus</i> and RPW_APPLE; while black crosses represent the identified OTUs. The vectors represent the mean direction and strength of correlation of diet and temperature (p-value < 0.05).</p

Similarity among the weevil-associated bacterial communities.

<p>A: principal-coordinate analysis on the phylogenetic β-diversity matrix obtained starting from the OTU table. The explained variance is as follows: 28.3% 1^st component, 14.3% 2^nd component. B: hierarchical clustering dendrogram representing the OTU table pairwise dissimilarities between the different analyzed weevils; the pie charts represent the relative abundance of bacterial communities at phylum level.</p

Effects of the diet on the microbiota of the red palm weevil (Coleoptera: Dryophthoridae)

Rhynchophorus ferrugineus, also known as the red palm weevil, is regarded as the major pest of palm trees. Although studies of the microbiota associated with this species have been performed in recent years, little attention has been dedicated to the influence of the diet in shaping the host bacterial community. Here, we investigated the influence of food sources (i.e. palm tissues vs apple based substrate) on the microbial diversity associated with RPW, which was compared with the microbiota associated with wild individuals of the sister species Rhynchophorus vulneratus. The bacterial characterization was performed using a culture independent approach, i.e. the 16S rRNA pyrotag, and a culture dependent approach for a subset of the samples, in order to obtain bacterial isolates from RPW tissues. The bacterial community appeared significantly influenced by diet. Proteobacteria resulted to be the most abundant clade and was present in all the specimens of the three examined weevil groups. Within Proteobacteria, Enterobacteriaceae were identified in all the organs analysed, including hemolymph and reproductive organs. The apple-fed RPWs and the wild R. vulneratus showed a second dominant taxon within Firmicutes that was scarcely present in the microbiota associated with palm-fed RPWs. A comparative analysis on the bacteria associated with the palm tissues highlighted that 12 bacterial genera out of the 13 identified in the plant tissues were also present in weevils, thus indicating that palm tissues may present a source for bacterial acquisition