Entomology Theses and Dissertations
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Item ODONATA SPECIES COMPOSITION IN AGROECOSYSTEMS: PRELIMINARY SURVEYS WITH AN EMPHASIS ON POTENTIAL FOR BIOLOGICAL CONTROL ON FARMS(2024) Hartman, Margaret Elizabeth; Lamp, William O; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Adult dragonflies and damselflies are efficient aerial predators that provide ecosystem service as consumers of pest arthropods. However, their role as predators of agricultural pests in agroecosystems has been understudied. The prey of odonates has been historically difficult to quantify but new molecular methods can make diet analysis easier. I conducted visual encounter surveys across four farms in 2020 and 2021. I found odonates were present on all farms surveyed but there were significant differences in abundance and richness. Fecal pellets were collected from 94 odonates in 2021 for prey DNA analysis using next generation sequencing. Nine odonate samples produced exceptional libraries, resulting in a large quantity of identifiable prey sequences. This preliminary study can help future researchers develop best practices for maintaining healthy farm water bodies and optimizing fecal DNA analysis methodology to better understand odonates’ potential for agricultural pest suppression.Item INVESTIGATING PAIR-RULE GENE ORTHOLOGS IN AN INTERMEDIATE GERM BEETLE, DERMESTES MACULATUS(2017) Xiang, Jie; Pick, Leslie; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Insects share a body plan based on repeating segments. Segmentation has been well characterized in Drosophila melanogaster, in which segments are established by a genetic hierarchy including gap, pair-rule and segment polarity genes. Pair-rule genes (PRGs) are a key class of segmentation genes as they are the first cohort of genes expressed in a periodic pattern. Segments are established simultaneously in Drosophila in early embryos, while most other insects add segments sequentially as the embryo elongates. Our goal is to understand molecular mechanisms controlling segment formation and to determine the extent of their conservation during evolution. Here, we established the hide beetle Dermestes maculatus, an intermediate germ developer, as a new model system for studying segmentation patterning. We first established a lab colony and studied early embryogenesis in Dermestes. All nine PRG orthologs were isolated using degenerate PCR and RACE, and their expression patterns were examined with in situ hybridization. Except for opa, all Dermestes PRG orthologs are expressed in PR-like striped patterns. Gene functions were tested using RNA interference (RNAi). We examined both hatched and unhatched larvae to uncover defects with different severities. Both Dmac-prd and -slp knockdown resulted in typical PR defects, suggesting that they are “core” PR genes. Dmac-eve, -run and -odd have dual roles in germ band elongation and in PR segmentation, as severe knockdown caused anterior-only, asegmental embryos while moderate knockdown resulted in PR-like defects. Elongated but asegmental germ bands resulted from Dmac-prd and -slp double knockdown, suggesting decoupling of germ band elongation and PR segmentation. Extensive cell death prefigured the cuticle patterns after knockdowns, seen long ago for Drosophila PR phenotypes, although disrupted cell mitosis was also observed after Dmac-eve knockdown. We propose that PRGs have retained basic roles in PR segmentation during the transition from short-to-long germ development and share evolutionary conserved functions in promoting cell viability. Finally, I also present detailed protocols on Dermestes lab rearing, embryo collection and fixation, in situ hybridization and RNAi. The technical information described here will provide useful information for other genetic studies in this new model system.Item SYSTEMATICS OF THE CRYPTIC FUNGUS-FARMING ANT GENUS Myrmicocrypta FR. SMITH, WITH THE DESCRIPTION OF A NEW GENUS AND SPECIES OF FUNGUS-FARMING ANTS (HYMENOPTERA: MYRMICINAE).(2014) Sosa-Calvo, Jeffrey; Mitter, Charles; Schultz, Ted R; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Fungus-farming ants (Hymenoptera: Formicidae) have become model systems for exploring questions regarding the evolution of symbiosis. However, robust phylogenetic studies of both the ants and their cultivars are needed to address whether or not the attine ant symbiosis is a result of strict or diffuse coevolution. Chapter One, deals with the relationships of the species within the ant genus Myrmicocrypta, and their fungal cultivars. Analyses conducted, recovered the genus as monophyletic and the sister group of Mycocepurus. In addition, the species M. tuberculata was recovered as the sister to the rest of Myrmicocrypta. The time-calibrated phylogeny recovered the age of stem-group Myrmicocrypta plus its sister group as 35.16 Ma, whereas the inferred age for the crown-group Myrmicocrypta was recovered at 30.05 Ma. Chapter Two, represents the first species-level taxonomic revision of the fungus-farming ant genus Myrmicocrypta. Myrmicocrypta is distributed in the New World tropics from Mexico to northern Argentina, and, as far as it is known, absent in the Caribbean and in the fossil record. Sixty-five species are recognized, of which 37 are described as new species. The revision includes a taxonomic key to the species of Myrmicocrypta based on the worker caste. When possible, descriptions and photographs of the reproductive forms (i.e., queens and males), geographic distribution, and notes on natural history are presented. Finally, Chapter Three, deals with the description of Cyatta abscondita, a new genus and species of fungus-farming ant from Brazil, based on morphological study of more than 20 workers, two dealate gynes, one male, and two larvae. Ecological field data are summarized, including natural history, nest architecture, and foraging behavior. Phylogenetic analyses of DNA sequence data from four nuclear genes indicate that C. abscondita is the distant sister taxon of the genus Kalathomyrmex, and that together they comprise the sister group of the remaining neoattine ants, an informal clade that includes the conspicuous and well-known leaf-cutter ants. Morphologically, C. abscondita shares very few obvious character states with Kalathomyrmex. It does, however, possess a number of striking morphological features unique within the fungus-farming tribe Attini. It also shares morphological character states with taxa that span the ancestral node of the Attini. The morphology, behavior, and other biological characters of C. abscondita are potentially informative about plesiomorphic character states within the fungus-farming ants and about the early evolution of ant agriculture.