Abstract
Insect–plant associations and their role in diversification are mostly studied in specialists. Here, we aimed to identify macroevolution patterns in the relationships between generalists and their host plants that have the potential to promote diversification. We focused on the Bemisia tabaci species complex containing more than 35 cryptic species. Mechanisms for explaining this impressive diversification have focused so far on allopatric forces that assume a common, broad, host range. We conducted a literature survey which indicated that species in the complex differ in their host range, with only few showing a truly broad one. We then selected six species, representing different phylogenetic groups and documented host ranges. We tested whether differences in the species expression profiles of detoxification genes are shaped more by their phylogenetic relationships or by their ability to successfully utilize multiple hosts, including novel ones. Performance assays divided the six species into two groups of three, one showing higher performance on various hosts than the other (the lower performance group). The same grouping pattern appeared when the species were clustered according to their expression profiles. Only species placed in the lower performance group showed a tendency to lower the expression of multiple genes. Taken together, these findings bring evidence for the existence of a common detoxification “machinery,” shared between species that can perform well on multiple hosts. We raise the possibility that this “machinery” might have played a passive role in the diversification of the complex, by allowing successful migration to new/novel environments, leading, in some cases, to fragmentation and speciation.
Highlights
Species complexes, including cryptic ones, are present in a wide range of taxonomic groups and are being discovered at an increasing rate (Bickford et al, 2007)
We present here three independent lines of evidence to suggest that species within the B. tabaci complex differ both in their ability to accept or utilize multiple plant hosts and in their detoxification expression patterns
Our literature survey of field-collection data clearly indicated that only a few species in the complex can be found on hosts from multiple botanical families, while the majority of species were limited to only few families
Summary
Species complexes, including cryptic ones, are present in a wide range of taxonomic groups and are being discovered at an increasing rate (Bickford et al, 2007). Examination of such closely-related species groups is considered to be the best experimental approach for studying the evolution of different degrees of generalism or specialism and their putative derived effects on divergence and speciation processes (Forister et al, 2012; Nyiln & Janz, 2009; Nyman, 2010). This is because species complexes tend to share a common genetic background, with biological differences mainly associated with their feeding ecology, avoiding the “phylogenetic noise” present when comparing phylogenetically distant taxa that have accumulated more diverse adaptations (Roy et al, 2016)
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