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Title:A contribution to species delimitation and taxonomy of North American Entomobrya (Collembola: Entomobryidae)
Author(s):Katz, Aron
Advisor(s):Soto-Adames, Felipe N.
Department / Program:Entomology
Degree Granting Institution:University of Illinois at Urbana-Champaign
cytochrome oxidase I (COI)
cryptic species
species delimitation
Abstract:Recent molecular phylogenetic studies have revealed that Collembola diversity estimates based on morphological characters have been greatly underestimated. High levels of DNA sequence divergence among congeneric species suggest that circumscription of species based solely on traditional morphological and color pattern characters provide a very conservative estimate of actual species diversity. Many described species in the genera Orchesella, Isotomurus and Lepidocyrtus have been shown to comprise complexes of several morphologically cryptic species diagnosable by color pattern. The genus Entomobrya includes many species marked by distinct, often complex, and variable color patterns, but to date, no one has explored the possible presence of cryptic species using DNA sequencing within this group. In order to evaluate the association between color pattern and molecular variation and test the hypothesis that color forms within Entomobrya morphospecies represent distinct species, a phylogenetic analysis of the complete cytochrome oxidase I gene (COI) was performed for 11 species of North American Entomobrya, including 13 color forms representing 4 morphospecies with different levels of color pattern variation: Entomobrya assuta, E. clitellaria, E. ligata, and E. quadrilineata. The analysis reveals genetic divergences as high as 18.5% between different color forms of the same morphospecies, equivalent to distances exhibited between species differentiated by morphology. However, genetic divergence did not always correlate with color pattern variation, leading to the conclusion that the diagnostic utility of color pattern is species dependent and requires evaluation individually for each species. Following an integrative framework for species delimitation based on explicit species criteria developed for this study, 3 morphologically cryptic lineages, each diagnosable by color pattern, are identified and supported by evidence obtained from phylogeny, genetic distances, geographic distribution, and color pattern. The chaetotaxy of 15 species of Eastern North American Entomobrya is redescribed in order to determine potential characters for the diagnosis of the new cryptic lineages and evaluate the diagnostic and phylogenetic utility of chaetotaxy. As a result, 4 new species are described, and new diagnoses are provided for E. assuta, E. atrocincta, E. decemfasciata, E. quadrilineata, E. ligata and E. multifasciata. Furthermore, previously undocumented levels of intraspecific variation in macrosetal pattern are reported, tempering the exclusive use of chaetotaxy for species delimitation. Phylogenetic relationships, estimated using both morphological and molecular data, indicate that Entomobrya is likely paraphyletic. The phylogenies also suggest that unreliable character homology, likely fostered by Entomobrya’s profusion of macrosetae, may limit the phylogenetic utility of chaetotaxy in groups characterized by an abundance of dorsal macrosetae.
Issue Date:2013-05-24
Rights Information:Copyright 2013 Aron D. Katz
Date Available in IDEALS:2013-05-24
Date Deposited:2013-05

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