Thesis
Cryptic diversity and evolution in a genus of oak-gall-associated parasitoid wasps
University of Iowa
Master of Science (MS), University of Iowa
Summer 2021
DOI: 10.17077/etd.005990
Abstract
Parasites tend to be host specialists. While a generalist strategy confers access to more potential hosts, the evolution of habitat-specific adaptations may improve fitness on one or a few similar hosts, leading to specialized host-associations. This can be especially true when host niches vary across multiple ecological axes that may be relevant for successful parasitism. One example of such hosts are oak galls, which are induced by gall-forming cynipid wasps, and exploited by parasitic insects. Oak galls are highly diverse across several dimensions including their external and internal morphology, phenology, and chemistry. Such variability among gall traits should theoretically drive parasites toward specialization. It is therefore unexpected that some oak-gall-associated parasite species are described as attacking many different galls. The Hymenopteran parasitoid species Ormyrus labotus attacks galls of >65 cynipid gallformers, with rearing records spanning more than 65 host galls associated with a diverse set of oak tree species and plant tissues, making it an apparent generalist with an unusually large host range. In this work, I used an integrative approach pairing molecular tools with morphological and ecological data to test whether O. labotus is truly a single generalist species, and how host use has evolved in the Ormyrus genus broadly. I find evidence that a few Ormyrus species, including O. labotus, are complexes of many specialist species, each with a much more restricted host range. Investigating cryptic diversity is crucial for accurate species estimates, improving our understanding of how lineages diversify, and designing effective biocontrol strategies against invasive species, like many galling wasps.
Details
- Title: Subtitle
- Cryptic diversity and evolution in a genus of oak-gall-associated parasitoid wasps
- Creators
- Sofia Iqbal Sheikh
- Contributors
- Andrew A Forbes (Advisor)Bin Z He (Committee Member)John M Logsdon (Committee Member)
- Resource Type
- Thesis
- Degree Awarded
- Master of Science (MS), University of Iowa
- Degree in
- Integrated Biology
- Date degree season
- Summer 2021
- DOI
- 10.17077/etd.005990
- Publisher
- University of Iowa
- Number of pages
- vii, 69 pages
- Copyright
- Copyright 2021 Sofia Iqbal Sheikh
- Language
- English
- Description illustrations
- color illustrations
- Description bibliographic
- Includes bibliographical references (pages 45-54).
- Public Abstract (ETD)
Parasitism, wherein one organism exploits another, is the most common life history strategy in all of life. Few organisms lack parasites, and many parasites tend to have life histories strongly associated with just one or a few similar hosts – i.e., they are specialists. The success of parasites as measured by their species richness and abundance is often attributed to this extreme level of specialization. Among parasitic organisms, parasitic insects, and in particular parasitoid wasps (which lay their eggs in other insects and are lethal to the host), are incredibly diverse but most species have not been studied in detail. Oddly for parasites, many parasitoid species are described as being associated with a large variety of hosts; in other words, they are apparently generalists (an evolutionary strategy wherein multiple, and often ecologically and chemically dissimilar, hosts can be exploited). However, because few of these generalists have been studied in any great detail, it is possible that many supposed generalist species might consist of several specialized and morphologically cryptic lineages. In this thesis, I investigated one such supposed generalist parasitoid, Ormyrus labotus, and other wasps in the genus Ormyrus associated with oak gall wasps. Oak gall wasps are a hyper-diverse group of herbivorous insects that induce abnormal structures (galls) on oak trees. Oak galls vary considerably in their ecology, morphology, and chemistry. Despite these differences, O. labotus is described as attacking 65 species of oak gall wasps. To test whether O. labotus is one generalist species, I used a molecular approach in combination with morphological and ecological data and found evidence for 35-36 species within several previously names species of Ormyrus, including 19-20 species matching the description of O. labotus. This study, alongside several other recent studies, highlight the need to investigate cryptic diversity to better estimate species diversity and understand the ecological interactions that structure host use by parasites.
- Academic Unit
- Biology
- Record Identifier
- 9984124170702771
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