Entomology

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    Should I Eat or Should I Go? Acridid Grasshoppers and Their Novel Host Plants: Potential for Biotic Resistance
    (MDPI, 2018-10-07) Avaneysan, Alina
    Novel, non-coevolved associations between introduced plants and native insect herbivores may lead to changes in trophic interactions in native communities, as well as to substantial economic problems. Although some studies in invasion ecology demonstrated that native herbivores can preferentially feed on introduced plants and therefore contribute to the biotic resistance of native communities to plant invasions, the role of acridid grasshoppers as native generalist insect herbivores is largely overlooked. This systematic review aimed to identify patterns of grasshopper feeding preferences for native versus introduced plants and, consequently, a potential of grasshoppers to provide biotic resistance of native communities. The analysis of 63 records of feeding preference trials for 28 North-American grasshopper species (retrieved from 2146 studies published during 1967–2017) has demonstrated a preference of grasshoppers for introduced host plants, and identified 12 preferred introduced plants with high or middle invasive ranks. A significant effect of the life stage (p < 0.001), but not the experimental environment, plant material, and measurements, on grasshopper preferences for introduced plants was also detected. Overall, results suggest a potential of acridid grasshoppers to contribute to the biotic resistance of native communities. The review also provides methodological recommendations for future experimental studies on grasshopper-host plant interactions.
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    Use of Molecular Gut Content Analysis to Decipher the Range of Food Plants of the Invasive Spotted Lanternfly, Lycorma delicatula
    (MDPI, 2020-04-01) Avanesyan, Alina; Lamp, William O.
    Spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), is an introduced highly invasive insect pest in the US that poses a significant risk to forestry and agriculture. Assessing and predicting plant usage of the lanternfly has been challenging, and little is known regarding the lanternfly nymph association with its host plants. In this study, we focused on: (a) providing a protocol for using molecular markers for food plant identification of L. delicatula; (b) determining whether the ingested plant DNA corresponds with DNA of the plants from which the lanternfly was collected; and, (c) investigating the spectrum of ingested plants. We utilized gut contents of third and fourth instar nymphs that were collected from multiple plants; we isolated ingested plant DNA and identified consumed plants. We demonstrated that (a) up to 534 bp of the rbcL gene from ingested plants can be detected in L. delicatula guts, (b) ingested plants in ~93% of the nymphs did not correspond with the plants from which the nymphs were collected, and (c) both introduced and native plants, as well as woody and non-woody plants, were ingested. This information will aid effective the monitoring and management of the lanternfly, as well as predict the lanternfly host plants with range expansion.
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    Diverse Host Plants of the First Instars of the Invasive Lycorma delicatula: Insights from eDNA Metabarcoding
    (MDPI, 2022-06-10) McPherson, Cameron; Avanesyan, Alina; Lamp, William O.
    Identification of host plants of the invasive spotted lanternfly, Lycorma delicatula (Hemiptera: Fulgoridae), has been the focus of many studies. While the adults and late nymphs are relatively easy to observe on plants and to use for molecular gut-content analysis, studying the early instars is more challenging. This study is the continuation of our ongoing efforts to determine the host range for each developmental stage of L. delicatula. In the present study, we focused exclusively on the first nymphal instars, and we used a novel approach, utilizing “bulk” DNA extracts for DNA metabarcoding of nymphal gut contents, to identify all the detectable plants that the nymphs had ingested prior to being collected. We were able to obtain high-quality amplicons (up to 406 bp) of a portion of the rbcL gene and detect 27 unique ingested plant species belonging to 17 families. Both native and introduced plants with the prevalence of trees and grasses were present among the ingested plants. We also identified 13 novel host plants that have not been previously reported for L. delicatula on the U.S. territory. The results from our study have important applications for developing effective programs on early monitoring of invasive L. delicatula.
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    Analysis of Plant Trait Data of Host Plants of Lycorma delicatula in the US Suggests Evidence for Ecological Fitting
    (MDPI, 2022-11-29) Avanesyan, Alina; McPherson, Cameron; Lamp, William O.
    Plant traits, used by the invasive insect herbivores to find and select suitable hosts, can play an important role in insect host range expansion. With regard to invasive Lycorma delicatula, it is not well explored, however, how the plant origin affects insect host selection, and whether native and introduced host plants differ in their morphology, lifespan, as well as environmental requirements for growth. We addressed this issue in our study through the comprehensive assessment of 25 relevant plant traits (a total of 27,601 records retrieved from the TRY database), as well as the origin and phylogenetic relationships of 37 host plants of L. delicatula in the U.S. Our results showed that only leaf area, leaf chlorophyll content, and canopy size were significantly greater in the introduced hosts than that in native plants. We did not detect a significant effect of the plant origin on other characteristics. Additionally, no significant differences between native and introduced hosts of L. delicatula in genetic distances from introduced Ailanthus altissima (the most preferred host) were detected. These results, for the first time, suggest strong evidence for ecological fitting which might drive the host plant selection of L. delicatula and its rapid spread in the U.S.
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    Phylogeography of an introduced insect pest and consequences of an insect introduction
    (2007-03-06) Ahern, Robert; Raupp, Micheal J; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Adelges cooleyi (Hemiptera: Adelgidae), a host-alternating gall-making insect pest native to the Rocky Mountains and Pacific Northwest and introduced into the eastern United States during the mid-19th century, was studied to address questions about phylogeography, to determine effects of introduction on genotypic and phenotypic variation, and to compare genetic variation associated with host use in native and introduced ranges. In Chapter One, sequence data from two mitochondrial (mtDNA) genes and amplified fragment length polymorphisms (AFLPs) were used to quantify the structure of genetic variation in the insect's native range. Several well-supported, divergent mtDNA lineages were identified. The structure of genetic variation among sampled locations is consistent with patterns shaped by glaciations. Samples from the southern edge of the insect's distribution are genetically isolated from the rest of the species, and hybridization of divergent mtDNA lineages via secondary contact was inferred from AFLP data. Changes in genetic and phenotypic variation associated with introduction were quantified in Chapter Two. Introduced populations had decreased genetic variation relative to native populations. Variation in an ecologically important trait, host preference, was also significantly lower in introduced populations than in native populations. An association between mtDNA haplotypes and host preference was identified. Adelges cooleyi in the eastern US have low genetic and phenotypic variation but appear to be sufficiently adapted for persistence. My results call into question the utility of neutral genetic variation to assess the probability of persistence in new environments by introduced species. Host-plants that A. cooleyi requires to complete its lifecycle are not native to the eastern US and occur together in patches that are often widely separated. In Chapter Three, analyses of mtDNA and AFLP genetic variation were conducted to determine the distribution of genetic variation within and among host plants in the native range and identify discrepancies that may be consistent with an incomplete lifecycle in the introduced range. Distribution of genetic variation within and among host-plants in the introduced range was not significantly different than that in the native range, as indicated by fixation indices, and I found no evidence for asexual populations in the introduced range.