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Mikó I, Friedrich F, Yoder MJ, Hines HM, Deitz LL, Bertone MA, Seltmann KC, Wallace MS, Deans AR. On dorsal prothoracic appendages in treehoppers (Hemiptera: Membracidae) and the nature of morphological evidence. PLoS One 2012; 7:e30137. [PMID: 22272287 PMCID: PMC3260216 DOI: 10.1371/journal.pone.0030137] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 12/10/2011] [Indexed: 12/02/2022] Open
Abstract
A spectacular hypothesis was published recently, which suggested that the "helmet" (a dorsal thoracic sclerite that obscures most of the body) of treehoppers (Insecta: Hemiptera: Membracidae) is connected to the 1st thoracic segment (T1; prothorax) via a jointed articulation and therefore was a true appendage. Furthermore, the "helmet" was interpreted to share multiple characteristics with wings, which in extant pterygote insects are present only on the 2nd (T2) and 3rd (T3) thoracic segments. In this context, the "helmet" could be considered an evolutionary novelty. Although multiple lines of morphological evidence putatively supported the "helmet"-wing homology, the relationship of the "helmet" to other thoracic sclerites and muscles remained unclear. Our observations of exemplar thoraces of 10 hemipteran families reveal multiple misinterpretations relevant to the "helmet"-wing homology hypothesis as originally conceived: 1) the "helmet" actually represents T1 (excluding the fore legs); 2) the "T1 tergum" is actually the anterior dorsal area of T2; 3) the putative articulation between the "helmet" and T1 is actually the articulation between T1 and T2. We conclude that there is no dorsal, articulated appendage on the membracid T1. Although the posterior, flattened, cuticular evagination (PFE) of the membracid T1 does share structural and genetic attributes with wings, the PFE is actually widely distributed across Hemiptera. Hence, the presence of this structure in Membracidae is not an evolutionary novelty for this clade. We discuss this new interpretation of the membracid T1 and the challenges of interpreting and representing morphological data more broadly. We acknowledge that the lack of data standards for morphology is a contributing factor to misinterpreted results and offer an example for how one can reduce ambiguity in morphology by referencing anatomical concepts in published ontologies.
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Affiliation(s)
- István Mikó
- Insect Museum, Department of Entomology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Frank Friedrich
- Biocenter Grindel and Zoological Museum Hamburg, Hamburg University, Hamburg, Germany
| | - Matthew J. Yoder
- Insect Museum, Department of Entomology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Heather M. Hines
- Department of Genetics, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Lewis L. Deitz
- Insect Museum, Department of Entomology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Matthew A. Bertone
- Insect Museum, Department of Entomology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Katja C. Seltmann
- Insect Museum, Department of Entomology, North Carolina State University, Raleigh, North Carolina, United States of America
| | - Matthew S. Wallace
- Biological Sciences, East Stroudsburg State University, East Stroudsburg, Pennsylvania, United States of America
| | - Andrew R. Deans
- Insect Museum, Department of Entomology, North Carolina State University, Raleigh, North Carolina, United States of America
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