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Title:Morphology of Acercaria: investigations of the ovipositor and internal anatomy
Author(s):Austin, Chip
Advisor(s):Dietrich, Christopher H.
Department / Program:Entomology
Degree Granting Institution:University of Illinois at Urbana-Champaign
internal anatomy
Abstract:Acercaria, which includes Psocodea, Thysanoptera and Hemiptera, is a group that encompasses substantial diversity and has generated equally substantial debate about its higher-level phylogeny. The advent of molecular phylogenetics has done little to resolve arguments about the placement of various infraorders within Hemiptera, in spite of general confidence about their monophyly, which illustrates the need to take integrative approaches that include morphology as well as conduct more analyses across these higher groups as a whole. This thesis will attempt to address some of these issues in hemipteroid morphological research through projects covering two main topics. The first chapter reviews and updates previously described morphology with a treatment focusing on the ovipositor. By comparing ovipositors among representatives of Hemiptera's infraorders and describing their character states using a common lexicon for homologous structures, it became apparent that "laciniate" (plant-piercing) ovipositors vary in such a way that implies such a phenotype was independently derived in the lineages that have them. This not only demonstrates the limited usefulness in the terms "laciniate" and "platelike" to describe hemipteran ovipositor types, but also provides support to the historically-held hypothesis that the earliest heteropterans had substantially different a life history and reproductive ecology from its relatives in Cicadomorpha and Fulgoromorpha. The second chapter describes an effort to investigate digestive and nerve tissue morphology, which has previously been hypothesized to be phylogenetically informative in acercarians (Goodchild 1966; Niven et al 2009). X-ray micro-computed tomography was used instead of conventional dissection for this task, which allowed for the 3-D visualization of these tissues with their natural placements and arrangements kept intact. These resulting images were found to align with previous dissections of closely related taxa where available; in addition, potential phylogenetic signal was found in the abdominal and thoracic neuromeres, the fusion of which varied among taxa. Although more taxon sampling would be needed to verify how phylogenetically informative characters of the nervous system may be, the results here demonstrate the great potential for microCT imaging in opening and exploring novel and neglected avenues of morphological investigation.
Issue Date:2016-07-22
Rights Information:Copyright 2016 Chip Austin
Date Available in IDEALS:2016-11-10
Date Deposited:2016-08

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