Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

Lowell E. Urbatsch

Abstract

The current taxonomic study of Indigofera (Fabaceae) as it occurs in the New World has several aims. The first addresses taxonomic and nomenclatural issues related to North American taxa. Because such issues have not been well understood for many of these taxa at various ranks, a synopsis of all taxa known to be referable to North America is presented along with a thorough discussion of nomenclatural issues (including synonymy) for each. This discussion is initially placed within the framework of the species groups proposed by Rydberg in 1923. A preliminary cladistic analysis of these North American species groups is presented. In that analysis, woody species with opposite leaflets are basal with Platycarpae (possessing flat pods) most basal; the perennial herbaceous species (including Leptosepalae) are most highly derived. Certain difficult species groups are examined and discussed, most notably the Leptosepalae. As a result of preliminary phenetic and starch gel electrophoretic analyses and a subsequent examination of herbarium specimens, Leptosepalae is considered to represent one widespread morphologically variable taxon (I. miniata), occurring from Guatemala to the United States and Cuba. Further, starch gel electrophoresis was employed to examine U.S. populations within this complex. Using morphological and electrophoretic evidence, one taxon (I. texana) included within the Leptosepalae is excluded and maintained as a separate species. An overview of the taxonomy of South American taxa is presented. Taxonomic history, nomenclature, synonymy, and opinion of the status of each taxon are presented. Species groups that are unifoliolate or have alternate leaflets (e.g., I. asperifolia-bongardiana, I. campestris-latifolia-parodiana-retrusa, and I. tephrosioides) are examined in light of their affinity with the I. miniata complex of North America. No definitive conclusions can be drawn, however, without further study of South American material. Finally, in order to provide a complete accounting of all names which have been used for New World Indigofera, a discussion of doubtful or incompletely known taxa is presented. A number of names are excluded from Indigofera and correctly placed within other genera; the most significant of these is I. coronilloides, the correct name of which is Coursetia coronilloides.

Pages

387

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