Assessing adaptive winter behaviors of beneficial arthropods, with a focus on the long-distance migratory ecology of Nearctic hover flies (Diptera: Syrphidae)

Clem, Carl Scott

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https://hdl.handle.net/2142/113166 Copy

Description

Title

Assessing adaptive winter behaviors of beneficial arthropods, with a focus on the long-distance migratory ecology of Nearctic hover flies (Diptera: Syrphidae)

Author(s)

Clem, Carl Scott

Issue Date

2021-07-12

Director of Research (if dissertation) or Advisor (if thesis)

Harmon-Threatt, Alexandra N

Doctoral Committee Chair(s)

Harmon-Threatt, Alexandra N

Committee Member(s)

• Berenbaum, May R
• Suarez, Andrew V
• Ratcliffe, Susan T

Department of Study

Entomology

Discipline

Entomology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Insect migration
• hover fly
• Syrphidae
• stable isotopes
• morphometrics
• cold tolerance
• isoscapes
• pollination
• biological control
• natural enemy
• field border
• conservation biological control
• semi-natural habitat
• organic farming

Abstract

Temperate climates present significant challenges for many insects. During the winter, insects are met with freezing temperatures and lack of resources that are normally accessible during warmer months. Consequently, insects have evolved behavioral and physiological strategies for surviving winter. Some seek refugia and enter a state of diapause as eggs, larvae, pupae, and/or adults, while others may migrate to more favorable locations. In this dissertation, I examine several aspects of winter survival among beneficial predacious, parasitic, and pollinating arthropods. Chapters 1 and 2 are focused on the long-distance migratory ecology of Nearctic hover flies (Diptera: Syrphinae), while Chapter 3 examines the effects of field borders on arthropod natural enemy communities. Syrphid hover flies of the subfamily Syrphinae are an important group of arthropods. Adults are pollinators for a variety of crop and non-crop plant species, while larvae act as biological control agents for major crop pests such as aphids. Despite these benefits, major aspects of their life histories remain unknown, especially for taxa outside of Europe. For example, while several Palearctic hover fly species are known to migrate, this behavior is almost entirely unresearched in Nearctic hover flies. In Chapter 1, I examine evidence and mechanisms of migration among four hover fly species (Allograpta obliqua, Eupeodes americanus, Syrphus rectus, and Syrphus ribesii) common throughout eastern North America using a novel combination of stable hydrogen isotope (δ2H) analyses, morphological assessments, abundance estimations, and cold-tolerance assays. Non-local δ2H values obtained from hover fly specimens collected in central Illinois support the existence of long-distance fall migratory behavior among Eu. americanus and to a lesser extent S. rectus and S. ribesii. Elevated abundance of Eu. americanus during the expected autumn migratory time period further supports the existence of such behavior. Moreover, morphological analyses suggest that migratory Eu. americanus may exhibit a unique suite of morphological traits that decrease costs associated with long-distance flight. Finally, compared to the ostensibly non-migratory A. obliqua, Eu. americanus was significantly less cold-tolerant, a factor that may be related to migratory behavior. In Chapter 2, I examined how far these hover flies travel by assessing natal origins of the migratory Eu. americanus and non-migratory A. obliqua collected in northern Alabama. I built hover fly δ2H isoscapes using a calibration algorithm of water and hover fly tissues. I then used these isoscapes to assign grouped natal origins of hover flies using an IsoriX workflow. Consistent with Chapter 1, Eu. americanus was highly migratory whereas A. obliqua was mostly non-migratory. Several Eu. americanus specimens were estimated to have traveled between 1,000 and 3,000 km from the midwestern United States and Canada to Alabama. In Chapter 3, I examined the capacity of semi-natural field borders to support overwintering predacious and parasitic arthropods. Semi-natural field borders are frequently used in midwestern U.S. sustainable agriculture. These habitats are meant to help diversify otherwise monocultural landscapes and provision them with ecosystem services, including biological control. Predatory and parasitic arthropods (i.e., potential natural enemies) often flourish in these habitats and may move into crops to help control pests. However, detailed information on the capacity of semi-natural field borders for providing overwintering refuge for these arthropods is poorly understood. In this study, I used soil emergence tents to characterize potential natural enemy communities (i.e., predacious beetles, wasps, spiders, and other arthropods) overwintering in cultivated organic crop fields and adjacent field borders. I found higher abundance, greater species richness, and a distinct community composition of predatory and parasitic arthropods in field borders compared to communities in arable crop fields, which were generally poorly suited as overwintering habitat. Furthermore, potential natural enemies tended to be positively associated with forb cover and negatively associated with grass cover, suggesting that grassy field borders with less forb cover are less suitable as winter refugia. These results demonstrate that semi-natural habitats such as field borders can act as a source for many natural enemies on a year-to-year basis and are important for conserving arthropod diversity in agricultural landscapes.

Graduation Semester

2021-08

Type of Resource

Thesis

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http://hdl.handle.net/2142/113166

Copyright and License Information

Copyright 2021 C. Scott Clem

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