Date of Award:

5-1992

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Mary Barkworth

Committee

Mary Barkworth

Committee

Jeanne Chambers

Committee

Dennis Welker

Abstract

Two previously unidentified taxa of Stipa L. were evaluated morphologically, electrophoretically, and ecologically. The two 'new' taxa (tentatively referred to as "puzzlei" and "valdesii") were compared with five species from southwestern United States and northern Mexico (Stipa lobata Swallen, Stipa alta Swallen, Stipa scribneri Vasey, Stipa lettermanii Vasey, and Stipa nelsonii Scribner), all of which are considered to belong in the Achnatherum species-group. Anatomical and micromorphological features show that the 'new' taxa also belong in this species-group. Principal coordinate analyses of the morphological data showed that each of the seven taxa tended to occupy a distinct portion of the multivariate morphological space, but with some overlap between "puzzlei" and Stipa lobata, and "valdesii" and Stipa alta. Clustering analyses agreed with the principal coordinate analyses, with only individuals in the overlap being clustered into a group other than their designated group. The distance matrix, however, revealed that each of these overlap individuals was closest to another individual of its designated group, except in one instance. Discriminant function analyses of the morphological data showed that each taxon can be distinguished by a different set of characters.

All analyses show several clear breaks. Stipa scribneri, Stipa lettermanii, and Stipa nelsonii are distinct from each other as well as from the remaining four taxa. Stipa lobata and "puzzlei" form a group, and Stipa alta and "valdesii" form a group. Numerical analyses of the electrophoretic data show each taxon to be distinct, but no electrophoretic data for Stipa alta were available. The ecological data reveal no clearly distinct habitat preference differences between the taxa. Based on the results the individuals identified as "puzzlei" form a distinct taxon, separate from Stipa lobata, and should be recognized at the species level. Differences between Stipa alta and the individuals identified as "valdesii" are evident, but the separation is not as clear as that between Stipa lobata and "puzzlei." The data are not complete enough to recognize the "valdesii" individuals as a distinct taxon without electrophoretic data for Stipa alta. Consequently, the "valdesii" individuals will be placed as a subspecies of Stipa alta.

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