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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    Response of Five Miscanthus sinensis Cultivars to Grasshopper Herbivory: Implications for Monitoring of Invasive Grasses in Protected Areas
    (MDPI, 2021-12-25) Avanesyan, Alina; Lamp, William O.
    Introduced grasses can aggressively expand their range and invade native habitats, including protected areas. Miscanthus sinensis is an introduced ornamental grass with 100+ cultivars of various invasive potential. Previous studies have demonstrated that the invasive potential of M. sinensis cultivars may be linked to seed viability, and some of the physiological traits, such as growth rate. Little is known, however, about whether these traits are associated with response of M. sinensis to insect herbivory, and whether plant tolerance and resistance to herbivory vary among its cultivars; which, in turn, can contribute to the invasive potential of some of M. sinensis cultivars. To address this issue, in our study we explored the response of five cultivars of M. sinensis to herbivory by Melanoplus grasshoppers. We demonstrated that plant responses varied among the cultivars during a season; all the cultivars, but “Zebrinus”, demonstrated a significant increase in plant tolerance by the end of the growing season regardless of the amount of sustained leaf damage. Different patterns in plant responses from “solid green” and “striped/spotted” varieties were recorded, with the lowest plant resistance detected for “Autumn Anthem” in the cage experiment. Our results have important applications for monitoring low-risk invaders in protected areas, as well as for biotic resistance of native communities to invasive grasses.
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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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    Plant-insect interactions in a shifting coastal ecosystem: Avicennia germinans and its associated arthropods
    (2020) Nathan, Mayda; Gruner, Daniel S; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The climate’s role in determining where species occur is increasingly well understood, but our ability to predict how biotic interactions both influence and respond to species’ range shifts remains poor. This is particularly important when considering climate-change-driven range shifts in habitat-forming species like mangroves, given their impact on ecosystem structure and function. In this dissertation, I consider the arthropods associated with the black mangrove, Avicennia germinans, to explore whether patterns of arthropod diversity affect the rate of a plant’s range expansion, and, in turn, how a range-expanding plant alters arthropod communities in habitats where it is invading. Among arthropods with the potential to influence plants’ range dynamics, pollinators can directly affect plant reproduction and ability to spread into new territory. Breeding system experiments reveal that A. germinans relies on pollinators for full fruit set, and surveys along the Florida coast show a substantial northward decline in the overall frequency of pollinator visits to A. germinans flowers. However, the decline in abundance of some common pollinator taxa is partly offset by an increase in the frequency of other highly effective taxa. Furthermore, range-edge A. germinans produce more flowers than southern individuals, contributing to high range-edge fecundity and enabling range expansion. As a woody plant with nectar-producing flowers, A. germinans is a novel resource for arthropods in the salt marshes where it is encroaching. To understand arthropod community assembly on these frontier mangroves, and how mangrove presence affects marsh arthropod community composition, I compare arthropod communities in these adjacent vegetation types. Arthropods form distinct communities on mangroves and marsh vegetation, with at least one A. germinans specialist already present in this range-edge population. However, neither mangrove proximity nor the abundance of mangrove flowers appears to influence salt marsh arthropod community structure, indicating that mangrove encroachment may lead to a net increase in arthropod diversity in coastal regions by increasing habitat heterogeneity. In sum, plants that rely on pollinators can avoid range-edge reproductive failure by attracting a diverse group of pollinating taxa, and range-expanding plants can rapidly alter invaded communities by shaping diversity at very local scales.
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    Nutrient limitation and its consequences for performance and the homeostatic regulation of macronutrient composition in two phytophagous insects with divergent life-history strategies
    (2005-01-13) Huberty, Andrea; Denno, Robert F; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Insect herbivores have a decidedly higher nitrogen and phosphorus than their host plants, an elemental mismatch that places severe constraints on their ability to meet nutritional demands. This study examined the consequences of macronutrient (nitrogen and phosphorus) limitation for two wing-dimorphic, phloem-feeding planthoppers with very different life-history strategies: the sedentary <i>Prokelisia dolus</i> and the migratory <i>P. marginata</i>. As a consequence of the constraints dispersal imposes on ingestion capacity, I argue that species using dispersal as a strategy for acquiring limiting nutrients are unable to adequately obtain nutrients when dispersal is not an option. The effect of nitrogen and phosphorus limitation for planthopper performance (Chapter 1) and homeostatic regulation of macronutrient composition (Chapter 2) were determined, as were the constraints dispersal places on other traits (ingestion capability) used to cope with nutrient limitation (Chapter 3). The planthopper species responded differently to nutrient limitation. The survival, body size, and development rate of both species was adversely affected on nutrient-deficient host plants, but <i>P. marginata</i> was more negatively affected than <i>P. dolus</i>. Nitrogen was more limiting than phosphorus for both species. <i>Prokelisia marginata</i> was also less able to regulate its macronutrient composition (C:N:P) and incurred greater growth penalties than <i>P. dolus</i>. Overall, the migratory species was far more sensitive to nutrient limitation. Divergent life-history strategies (migratory versus sedentary) and the differential muscle allocation patterns associated with such strategies provide the mechanism underlying the consistently different performance responses of the two planthopper species on nutrient-deficient host plants. Morphometric and gravimetric measures of investment in flight versus feeding indicate that the sedentary <i>P. dolus</i> allocates more muscle mass to feeding whereas <i>P. marginata</i> invests more heavily in flight. Due to its greater investment in feeding musculature and associated enhanced ingestion rate, the immobile <i>P. dolus</i> is better equipped to meet macronutrient demands when faced with nutrient-poor food than the migratory <i>P. marginata</i>. Results of this research demonstrate the importance of considering life-history strategies, and associated constraints imposed on ingestion, when assessing how the macronutrient stoichiometry of plants (C:N:P content) interfaces with the nutritional requirements of phytophagous insects to affect their growth and performance.