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• Evolutionary history of host use, rather than plant phylogeny, determines gene expression in a generalist butterfly

  2016. Maria de la Paz Celorio-Mancera (et al.). BMC Evolutionary Biology 16

  Artikel

  Background: Although most insect species are specialized on one or few groups of plants, there are phytophagous insects that seem to use virtually any kind of plant as food. Understanding the nature of this ability to feed on a wide repertoire of plants is crucial for the control of pest species and for the elucidation of the macroevolutionary mechanisms of speciation and diversification of insect herbivores. Here we studied Vanessa cardui, the species with the widest diet breadth among butterflies and a potential insect pest, by comparing tissue-specific transcriptomes from caterpillars that were reared on different host plants. We tested whether the similarities of gene-expression response reflect the evolutionary history of adaptation to these plants in the Vanessa and related genera, against the null hypothesis of transcriptional profiles reflecting plant phylogenetic relatedness. Result: Using both unsupervised and supervised methods of data analysis, we found that the tissue-specific patterns of caterpillar gene expression are better explained by the evolutionary history of adaptation of the insects to the plants than by plant phylogeny. Conclusion: Our findings suggest that V. cardui may use two sets of expressed genes to achieve polyphagy, one associated with the ancestral capability to consume Rosids and Asterids, and another allowing the caterpillar to incorporate a wide range of novel host-plants.

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• Salivary Gland Secretions of Phytophagous Arthropods

  2016. Maria P. Celorio-Mancera, John M. Labavitch. Extracellular Composite Matrices in Arthropods, 601-623

  Kapitel

  Thousands of arthropod species use plants as their main food source. Plants in turn are not completely passive towards arthropod herbivory. Arthropod saliva constitutes an important point of contact which initiates phytophagy and mediates chemical communication. Here we present a summary of those communications studying the constituents of arthropod saliva and their effect on plants. Particular attention has been dedicated to those reports identifying salivary gland genes and proteins in their entirety (transcriptomes and proteomes). The anatomy of salivary glands is highly variable and much of its complexity remains unstudied in various groups of phytophagous arthropods. Some important factors dictating the function of saliva in herbivory are the feeding strategy used by the arthropod, the developmental stage of the animal and the ecological niche in question. The function of many salivary components, such as the chemosensory proteins identified in arthropods, is still largely unknown. We consider the use of heterologous expression of these genes, chemoinformatic, molecular modeling and immunohistochemical studies to be of substantial importance for the elucidation of the functions of these genes as well as the functions of many other unknown proteins in arthropod systems. Additionally, the role of hemolymph proteins such as apolipophorins and storage proteins in saliva is unclear and therefore attention must be devoted to the understanding of protein movement in the arthropod body.

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• Why stay in a bad relationship? The effect of local host phenology on a generalist butterfly feeding on a low-ranked host

  2016. Hélène Audusseau (et al.). BMC Evolutionary Biology 16

  Artikel

  Background: In plant-feeding insects, the evolutionary retention of polyphagy remains puzzling. A better understanding of the relationship between these organisms and changes in the metabolome of their host plants is likely to suggest functional links between them, and may provide insights into how polyphagy is maintained. Results: We investigated the phenological change of Cynoglossum officinale, and how a generalist butterfly species, Vanessa cardui, responded to this change. We used untargeted metabolite profiling to map plant seasonal changes in both primary and secondary metabolites. We compared these data to differences in larval performance on vegetative plants early and late in the season. We also performed two oviposition preference experiments to test females' ability to choose between plant developmental stages (vegetative and reproductive) early and late in the season. We found clear seasonal changes in plant primary and secondary metabolites that correlated with larval performance. The seasonal change in plant metabolome reflected changes in both nutrition and toxicity and resulted in zero survival in the late period. However, large differences among families in larval ability to feed on C. officinale suggest that there is genetic variation for performance on this host. Moreover, females accepted all plants for oviposition, and were not able to discriminate between plant developmental stages, in spite of the observed overall differences in metabolite profile potentially associated with differences in suitability as larval food. Conclusions: In V. cardui, migratory behavior, and thus larval feeding times, are not synchronized with plant phenology at the reproductive site. This lack of synchronization, coupled with the observed lack of discriminatory oviposition, obviously has potential fitness costs. However, this opportunistic behavior may as well function as a source of potential host plant evolution, promoting for example the acceptance of new plants.

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