Evolution and ecology of associations between Drosophila and their parasitic nematodes

Persistent Link:
http://hdl.handle.net/10150/280144
Title:
Evolution and ecology of associations between Drosophila and their parasitic nematodes
Author:
Perlman, Steven
Issue Date:
2002
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
In this dissertation, the evolutionary and ecological determinants of host range of nematode parasites (Tylenchida: Allantonematidae: Howardula, Parasitylenchus) of mushroom-breeding Drosophila (Diptera: Drosophilidae) are examined. These nematodes are horizontally transmitted, obligate parasites, often with severe effects on host fitness. Phylogenetic analysis of Drosophila and Howardula DNA sequences shows little congruence between host and parasite phylogenies, with frequent host colonizations and losses. Drosophila -parasitic Howardula are not monophyletic, with host switches occurring between Drosophila and distantly related mycophagous sphaerocerid flies. Molecular analysis reveals eight new Howardula species. The ability of five nematode species to infect and develop in 24 taxonomically diverse Drosophila species is assessed. All nematode potential host ranges but one are large, even for host specialists. Novel hosts that are distantly related from the native host are less likely to be infected, but among closely related hosts there is variation in susceptibility. Potential host ranges differ greatly between related parasite species. Most novel infections do not cause reductions in host fecundity, with the exception of P. nearcticus. Thus, Drosophila-nematode associations are dynamic, and appear to be driven by a combination of repeated opportunities for host colonization due to shared mushroom breeding sites, and large nematode potential host ranges. Recent colonization of novel host species may explain the striking differences in virulence observed in natural Drosophila-nematode associations. For example, Nearctic species of the Drosophila testacea group are more severely affected by infection than Palearctic species, including complete female sterility. Cross-infection experiments reveal that virulence is evolutionarily labile in testacea-Howardula associations, and that high levels of virulence manifested in some host-parasite combinations are due to a lack of host resistance. Finally, ecological determinants of host range are considered. First, competition between a generalist and a specialist parasite of D. recens is assessed by comparing nematode infection success and reproduction in single and double infections. Second, differences between the actual and potential host ranges of Howardula neocosmis are documented. This parasite appears restricted to D. acutilabella in nature, yet successfully parasitizes the closely related, microsympatric D. cardini. Neither differential virulence nor competitive interactions between hosts explain the host range differences.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Ecology.; Biology, Entomology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Ecology and Evolutionary Biology
Degree Grantor:
University of Arizona
Advisor:
Jaenike, John

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleEvolution and ecology of associations between Drosophila and their parasitic nematodesen_US
dc.creatorPerlman, Stevenen_US
dc.contributor.authorPerlman, Stevenen_US
dc.date.issued2002en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractIn this dissertation, the evolutionary and ecological determinants of host range of nematode parasites (Tylenchida: Allantonematidae: Howardula, Parasitylenchus) of mushroom-breeding Drosophila (Diptera: Drosophilidae) are examined. These nematodes are horizontally transmitted, obligate parasites, often with severe effects on host fitness. Phylogenetic analysis of Drosophila and Howardula DNA sequences shows little congruence between host and parasite phylogenies, with frequent host colonizations and losses. Drosophila -parasitic Howardula are not monophyletic, with host switches occurring between Drosophila and distantly related mycophagous sphaerocerid flies. Molecular analysis reveals eight new Howardula species. The ability of five nematode species to infect and develop in 24 taxonomically diverse Drosophila species is assessed. All nematode potential host ranges but one are large, even for host specialists. Novel hosts that are distantly related from the native host are less likely to be infected, but among closely related hosts there is variation in susceptibility. Potential host ranges differ greatly between related parasite species. Most novel infections do not cause reductions in host fecundity, with the exception of P. nearcticus. Thus, Drosophila-nematode associations are dynamic, and appear to be driven by a combination of repeated opportunities for host colonization due to shared mushroom breeding sites, and large nematode potential host ranges. Recent colonization of novel host species may explain the striking differences in virulence observed in natural Drosophila-nematode associations. For example, Nearctic species of the Drosophila testacea group are more severely affected by infection than Palearctic species, including complete female sterility. Cross-infection experiments reveal that virulence is evolutionarily labile in testacea-Howardula associations, and that high levels of virulence manifested in some host-parasite combinations are due to a lack of host resistance. Finally, ecological determinants of host range are considered. First, competition between a generalist and a specialist parasite of D. recens is assessed by comparing nematode infection success and reproduction in single and double infections. Second, differences between the actual and potential host ranges of Howardula neocosmis are documented. This parasite appears restricted to D. acutilabella in nature, yet successfully parasitizes the closely related, microsympatric D. cardini. Neither differential virulence nor competitive interactions between hosts explain the host range differences.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Ecology.en_US
dc.subjectBiology, Entomology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineEcology and Evolutionary Biologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorJaenike, Johnen_US
dc.identifier.proquest3065509en_US
dc.identifier.bibrecord.b43038426en_US
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