Species-complex diversification and host-plant associations in Bemisia tabaci: a plant-defense, detoxification perspective revealed by RNAseq analyses. Species-complex diversification and host-plant associations in Bemisia tabaci: a plant-defense, detoxification perspective revealed by RNAseq analyses

Bemisia tabaci is a complex of > 35 cryptic species. The putative mechanisms driving this impressive diversification focus on allopatric forces that assume a common, broad, host-plant range. Our analyses, however, suggest that many species are much more host-specific, with only few showing a truly broad host-range. To ask if host-adaptation processes have played a role in B. tabaci diversification, we tested if differences in performance and in expression profiles of genes involved in host utilization (detoxification genes), are shaped more by the evolutionary history of the complex, or by the evolutionary history of the species-plant associations. Six species, representing different geographical regions and diet breadths were analyzed. Performance assays divided them into two groups, one showing higher performance on various host plants than the other. The same grouping pattern appeared when the species were clustered according to their expression profiles, despite the species in the higher-performance group being only distantly related phylogenetically. Species placed in the lower-performance group also showed reduced expression of common detoxification genes. These findings support an evolutionary model of species expansion involving alternations, in evolutionary time scales, between more “extended” and more “restricted” host-range phases and meet the predictions of the oscillation hypothesis.