A Phylogenetic Assessment of Thereva Latreille (Insecta: Diptera: Therevidae)
Holston, Kevin Cornell
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https://hdl.handle.net/2142/86442
Description
Title
A Phylogenetic Assessment of Thereva Latreille (Insecta: Diptera: Therevidae)
Author(s)
Holston, Kevin Cornell
Issue Date
2003
Doctoral Committee Chair(s)
Irwin, Michael E.
Department of Study
Entomology
Discipline
Entomology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Genetics
Language
eng
Abstract
The objective of this study is to develop a framework for biological research on Thereva (1) using molecular data to test a phylogenetic hypothesis that posits a monophyletic Thereva with respect to a diverse sample of genera in Therevinae, (2) using molecular and morphological data to propose a species-level phylogeny for Thereva to identify biogeographical patterns, and (3) using specimens and specimen label data to complete a taxonomic revision of Thereva for the Nearctic Region. The first phase of phylogenetic analyses addressed previous assertions that Thereva that is a polyphyletic assemblage (composed of several unrelated evolutionary therevine lineages), and involved study of 59 species representing 33 genera in the subfamily Therevinae. Using a molecular dataset of two nuclear genes (28S rDNA and elongation factor 1-alpha) and one mitochondrial gene (16S rDNA), a monophyletic circumscription of Thereva was identified that includes Afrotropical, Nearctic, and Palaearctic species and excludes Afrotropical and Neotropical species treated as Thereva by previous authors. The second phase of phylogenetic analyses examined species relationships within the monophyletic nominal clade of Thereva using two mitochondrial genes (16S and cytochrome oxidase I) and 33 morphological characters; these analyses included six outgroups and 37 Thereva ingroup species. The position of two major clades of Nearctic species and the position of a Far East Palaearctic species provided evidence for at least three Nearctic evolutionary radiations of Thereva that are derived with respect to Palaearctic species. The phylogenetic relationships from combined analyses support a biogeographic connection between the Nearctic and the eastern Palaearctic, and ten species groups of Thereva were identified. A revision of the Nearctic Thereva was developed to provide taxonomic information for recognizing and distinguishing among species. Eleven of the 35 Nearctic species were previously undescribed; one species, Thereva nobilitata (Fabricius), is introduced from the western Palaearctic Region. Characters of the male genitalia and the female frons are of primary importance in distinguishing species of Thereva and are illustrated for all species in the Nearctic Region. The nomenclature for species is updated, and lists of specimens examined and distribution maps are provided.
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