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Mol Ecol. 2015 Jun;24(11):2759-76. doi: 10.1111/mec.13191. Epub 2015 May 14.

Differences in performance and transcriptome-wide gene expression associated with Rhagoletis (Diptera: Tephritidae) larvae feeding in alternate host fruit environments.

Author information

1
Department of Entomology, Kansas State University, 123 W. Waters Hall, Manhattan, KS 66502, USA.
2
Environmental Change Initiative, University of Notre Dame, 1400 E. Angela Blvd., South Bend, IN 46617, USA.
3
Department of Biological Sciences, University of Notre Dame, 100 Galvin Life Sciences Center, Notre Dame, IN 46556, USA.
4
Department of Biology, Western Washington University, 510 High Street, MS 9160, Bellingham, WA, 98225, USA.
5
Department of Entomology and Nematology, University of Florida, 1881 Natural Area Drive, Gainesville, FL 32611, USA.

Abstract

Host race formation, the establishment of new populations using novel resources, is a major hypothesized mechanism of ecological speciation, especially in plant-feeding insects. The initial stages of host race formation will often involve phenotypic plasticity on the novel resource, with subsequent genetically based adaptations enhancing host-associated fitness differences. Several studies have explored the physiology of the plastic responses of insects to novel host environments. However, the mechanisms underlying evolved differences among host races and species remain poorly understood. Here, we demonstrate a reciprocal larval performance difference between two closely related species of Rhagoletis flies, R. pomonella and R. zephyria, specialized for feeding in apple and snowberry fruit, respectively. Microarray analysis of fly larvae feeding in apples versus snowberries revealed patterns of transcriptome-wide differential gene expression consistent with both plastic and evolved responses to the different fruit resources, most notably for detoxification-related genes such as cytochrome p450s. Transcripts exhibiting evolved expression differences between species tended to also demonstrate plastic responses to fruit environment. The observed pattern suggests that Rhagoletis larvae exhibit extensive plasticity in gene expression in response to novel fruit that may potentiate shifts to new hosts. Subsequent selection, particularly selection to suppress initially costly plastic responses, could account for the evolved expression differences observed between R. pomonella and R. zephyria, creating specialized races and new fly species. Thus, genetically based ecological adaptations generating new biodiversity may often evolve from initial plastic responses in gene expression to the challenges posed by novel environments.

KEYWORDS:

Rhagoletis; host adaptation; larval fitness; plant-insect interactions; speciation; transcriptome

PMID:
25851077
DOI:
10.1111/mec.13191
[Indexed for MEDLINE]

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