A biosystematic revision of the Nearctic species of the mayfly genus Isonychia (Ephemeroptera: oligoneuriidae)

dc.contributor.authorKondratieff, B. C.en
dc.contributor.committeechairVoshell, J. R., Jr.en
dc.contributor.committeememberEaton, John L.en
dc.contributor.committeememberHoffman, R. L.en
dc.contributor.committeememberKosztarab, Michaelen
dc.contributor.committeememberOpell, Brent D.en
dc.description.abstractThe Nearctic species of the genus Isonychia Eaton are revised. Eighteen species are recognized, of which three are described as new; eleven species names are placed in synonymy. Isonychia campestris McDunough is recognized as a fully valid geographically restricted species. Two subgenera, Isonychia sensu stricto and Prionoides Kondratieff and Voshell are recognized on the basis of adult and nymphal characteristics. Isonychia s.s. includes four species groups: bicolor group with four species, arida group with one species, sicca group containing five species, and diversa group with one species. The subgenus Prionoides includes seven species. A Neotype is designated for l. arida (Say). Previously undescribed characters of the nymphal gills are described and illustrated. The male genitalia and eggs are illustrated for every species. The distribution of each species is mapped. Diagnostic keys to male adults and nymphs are presented. A discussion of the nomenclatural history of the genus and each species is included. Diagnostic characters, rearing and collecting techniques are also discussed. The life histories and life cycles of two populations of Isonychia (Isonychia) bicolor (Walker) and one population of Isonychia (Prionoides) obscura Traver are presented in detail. Many features used in the past as specific criteria, especially in the bicolor and sicca Groups are found to be related to developmental periods of given populations involving geography, elevation, water temperature and stream size. The life cycle of I. bicolor is probably bivoltine at both sites. At the trout stream site there is a large-sized spring emerging generation and a much smaller summer emerging generation with considerable overlap. Isonychia obscura Traver is univoltine with adult emergence in mid-June and with egg diapause during the summer months. Additional life history information is also presented for I. (l.) tusculanensis Berner and I. (P.) serrata Traver. The evolution of the genus Isonychia and the two subgenera l. (Isonychia) and I. (Prionoides) is hypothesized. The North American biogeography of Isonychia may have included an invasion of North America via the "asiamerican" land mass of the Cretaceous. The early Isonychia mayflies may have been adapted to low order cool streams of high elevations. This lineage was probably similar to the subgenus Prionoides. Isonychia s.s. has been successful in colonizing the upper and lower austral zones and appears to be a warm water adapted group.en
dc.description.degreeDoctor of Philosophyen
dc.format.extentx, 312, [3] leavesen
dc.publisherVirginia Polytechnic Institute and State Universityen
dc.relation.isformatofOCLC# 8878438en
dc.rightsIn Copyrighten
dc.subject.lccLD5655.V856 1982.K764en
dc.titleA biosystematic revision of the Nearctic species of the mayfly genus Isonychia (Ephemeroptera: oligoneuriidae)en
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.nameDoctor of Philosophyen


Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
19.19 MB
Adobe Portable Document Format