Thesis
Does the genome of a putatively specialist moth (Schinia gracilenta) contain a signal of the Indigenous cultivation of its host plant (Iva annua)?
University of Iowa
Master of Science (MS), University of Iowa
Spring 2023
DOI: 10.25820/etd.007255
Abstract
When capabilities are limited for studying the demographic history of an organism directly, study of one of its parasites may provide useful insights because such parasites will have a shared geographic history with the organism of interest. I test this strategy using the slender flower moth (Schinia gracilenta Hübner 1818), an herbivorous insect that feeds on sumpweed (Iva annua L. 1753). Sumpweed is thought to have been cultivated in North American ca. 7000 B.P and domesticated by 4400 B.P, but limited archaeobotanical records cannot address potential range changes that may have occurred during the domestication process. To test whether S. gracilenta genomes can inform possible range changes, I collected S. gracilenta, and two congeners, Schinia rivulosa and Schinia thoreaui. These moths feed variously on Iva annua, Iva frutescens, Ambrosia artemisiifolia and Ambrosia trifida across the eastern half of the USA. I used Restriction-site Associated DNA sequencing (RAD-seq) to generate a phylogenetic tree of all moths using RAD-seq data and subsampled collections to make a secondary mitochondrial COI gene tree. Using population genetic methods, I determined the population structure of all Schinia collections from all host plants. Then I repeated population genetic analyses using a sample set restricted only to S. gracilenta moths.
Though I find that genetic distance increases with geographic distance between populations, I find no other notable population structure within S. gracilenta to indicate any range expansion of its host plant. I also find no evidence for a decrease in allelic diversity corresponding to increased distance from a presumed center or origin.
Although my data indicates no range expansion of I. annua, the conclusions drawn should be accepted cautiously. It is possible, for instance, that introgressed alleles from other Schinia species into I. annua may obscure a signal of range expansion. Second, though S. gracilenta is described as a specialist on I. annua, some individuals of this species were collected on other hosts. Though previous collections and experimental work suggest that Schinia moths are specialists, if they are not, S. gracilenta would not have the obligate symbiotic relationship required for detection of I. annua’s demographic history. With these caveats, my working hypothesis is that I. annua’s pre-domestication range likely extended to most of the places it is still found today, and that movement of domesticated forms did not increase its range – or the range of its associated moth parasite.
Details
- Title: Subtitle
- Does the genome of a putatively specialist moth (Schinia gracilenta) contain a signal of the Indigenous cultivation of its host plant (Iva annua)?
- Creators
- Wren Renquist
- Contributors
- Andrew A Forbes (Advisor)Maurine Neiman (Advisor)Andrew Kitchen (Committee Member)Stephen D Hendrix (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Integrated Biology
- Date degree season
- Spring 2023
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.007255
- Number of pages
- xiii, 99 pages
- Copyright
- Copyright 2023 Wren Renquist
- Language
- English
- Date submitted
- 04/20/2023
- Date approved
- 05/06/2023
- Description illustrations
- color illustrations, color maps
- Description bibliographic
- Includes bibliographical references (pages 94-99).
- Public Abstract (ETD)
When one species depends on another for survival, their histories will often be intertwined. For this reason, when it is not easy to directly study the history of one organism, we might be able to indirectly study it by instead studying the history of one of its parasites. Here I study the slender flower moth (Schinia gracilenta) and its host plant, sumpweed (Iva annua). Sumpweed is thought to have been cultivated in North America from 7000 years ago until 250 years ago. Its range may have been expanded during this time, but we currently have no strong evidence for or against this. I collected the slender flower moth and two other closely related moth species feeding on sumpweed, ragweed, and giant ragweed. I used Restriction-site Associated DNA sequencing (RAD-seq) to test whether the slender flower moth’s genomes contain signatures of a historical range expansion. Using DNA sequence data generated using RAD-seq, I created a phylogenetic tree, generated population summary statistics, and estimated population structure.
I found no evidence that the slender flower moth has undergone a recent range expansion. However, I also found some slender flower moths feeding on ragweed species, which were not previously known as hosts for these moths. It is possible, therefore, that the slender flower moth and sumpweed do not have the strictly obligate symbiotic relationship required for detection of a historical sumpweed expansion. I also detected evidence that the slender flower moth may occasionally produce hybrids with its two closest relatives, which may have affected interpretation of my genetic data. With these caveats, my working hypothesis is that sumpweed’s pre-domestication range likely extended to most of the places it is still found today, and that movement of domesticated forms did not increase its range – or the range of its associated moth parasite.
- Academic Unit
- Biology
- Record Identifier
- 9984428941202771
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