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Testing an Interference Competition Hypothesis to Explain the Decline of the Convergent Lady Beetle, Hippodamia convergens (Coleoptera: Coccinellidae), in Ohio

Smith, Chelsea A.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1339527346

Abstract Details

2012, Master of Science, Ohio State University, Entomology.
A significant decline in the abundance of the native coccinellid, Hippodamia convergens, coincides with the establishment and population increase of exotic coccinellids in Ohio. This pattern has lead to the hypothesis that intraguild predation by exotic lady beetles explains this decline. Several laboratory experiments demonstrating the propensity of exotic lady beetles to act as predators of native coccinellid eggs provide support for this hypothesis. The goal of this research was to determine the extent that exotic lady beetles predate on native coccinellid egg masses in the field. Two studies conducted over the course of three field seasons (2009-11), are presented in Chapters 2 and 3. Chapter 2 examines the extent of predation on coccinellid egg masses, and the role of coccinellids as egg predators. The objectives were to 1) compare the extent of egg predation experienced by three coccinellid species: H. convergens, Coleomegilla maculata, and Harmonia axyridis; 2) examine the levels of egg predation occurring across three habitats; and 3) determine the guild of predators responsible for coccinellid egg predation. To address these objectives, egg predation experiments were conducted in habitats where coccinellids are commonly found foraging: grassland, alfalfa, and soybean. Eggs of each focal coccinellid species were placed in the fields for 48 hours. The proportion of eggs remaining was compared among coccinellid species and habitats. Egg masses from the increasingly-rare native coccinellid, H. convergens, incurred significantly greater predation than eggs from the common exotic coccinellid, H. axyridis. Predation of the egg masses from the three species varied across habitats with the greatest amount of predation occurring in grasslands and the least in alfalfa. These egg predation experiments provided supporting evidence for the IGP hypothesis. Video surveillance systems were placed in the field and focused on coccinellid egg masses. These preliminary video experiments provided evidence that exotic coccinellids are not common predators of the egg masses. Chapter 3 details video experiments conducted to determine patterns among the predators contributing to coccinellid egg predation. The objectives of this study were to 1) measure the relative abundance and activity density of coccinellid egg predators present within the focal habitats 2) document the contribution of predator taxa to native and exotic lady beetle egg predation within each foraging habitat; and 3) determine if the relative abundance of aphids affects the intensity of egg predation. To address these objectives, video systems were used to observe predation of H. convergens and H. axyridis egg masses in soybean, alfalfa, and grassland habitats. The relative abundance and activity density of aphids and egg predators was also determined using quadrats, sweep samples, and pitfall traps. From the video observations, the guild of predators detected included Stylommatophora, Opiliones, Oniscidea, Coccinellidae, Gryllidae, Neuroptera, Tettigoniidae, Acrididae, Formicidae, Nabidae, Thripidae, Syrphidae, Araneae, Staphylinidae, and Diplopoda. This guild varied in diversity across the habitats, with the greatest diversity found within grassland habitats. Redundancy analysis revealed two egg predators that maintained a constant pattern of predation across both 2010 and 2011: Formicidae and Oniscidea.
Mary Gardiner, PhD (Advisor)
John Cardina, PhD (Committee Member)
Daniel Herms, PhD (Committee Member)
Andrew Michel, PhD (Committee Member)
137 p.
Biology; Conservation; Ecology; Entomology
intraguild predation; egg predation; biological control; Hippodamia convergens; Harmonia axyridis; Coccinellidae

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Citations

  • Smith, C. A. (2012). Testing an Interference Competition Hypothesis to Explain the Decline of the Convergent Lady Beetle, Hippodamia convergens (Coleoptera: Coccinellidae), in Ohio [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339527346

    APA Style (7th edition)

  • Smith, Chelsea. Testing an Interference Competition Hypothesis to Explain the Decline of the Convergent Lady Beetle, Hippodamia convergens (Coleoptera: Coccinellidae), in Ohio. 2012. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1339527346.

    MLA Style (8th edition)

  • Smith, Chelsea. "Testing an Interference Competition Hypothesis to Explain the Decline of the Convergent Lady Beetle, Hippodamia convergens (Coleoptera: Coccinellidae), in Ohio." Master's thesis, Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339527346

    Chicago Manual of Style (17th edition)

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© 2012, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.