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Flavonoid systematics of North American Lupinus species (Leguminosae)

University of British Columbia

This study was an assessment of the usefulness of flavonoids as taxonomic markers in the genus Lupinus (Leguminosae). The genus itself is readily recognizable, but, in North America, specific boundaries are poorly defined. This is probably the result of a combination of considerable morphological plasticity and hybridization (particularly amongst the outcrossing perennial taxa). At the outset, a detailed analysis of Lupinus flavonoids was made. Fifty-six compounds were identified, the majority being flavones based on apigenin, luteolin and less commonly acacetin and chrysoeriol. Glucose was the only sugar attached to flavonoids but was found C-bonded at the 6- or 8- positions and 0-bonded at the 5,7,3' or 4'-positions. Some flavonols and isoflavones were also identified. The reliability of flavonoids as specific characters was next tested. Fresh or dried plant material had identical flavonoid content, and plants of varying ages were chemically identical. Geographically, quantitative variation in flavonoid content was noted in an analysis of Lupinus sericeus by high pressure liquid chromatography. A sharp discontinuity in orientin levels was seen between populations north and south of Great Salt Lake, Utah, lending support to the subspecific ranking of the southerly population by Fleak (1971). Subsequent analysis of plants grown in uniform conditions showed the flavonoid differences to have been a phenotypic response. Since flavonoids appeared to be infraspecifically stable characters, an interspecific study of 73 taxa was made. Principal components analysis exposed 7 chemical groups. Six of these accumulated some novel flavonoids peculiar to each group. The seventh group had profiles containing no unusual compounds. One species (L. diffusus) had a very complex profile and was classed as a monospecific group. Using.the literature and personal observations it was seen that in 5 groups the chemical affinities paralleled morphological affinities thereby strengthening the integrity of the groups as natural units. Group C, however, was divided into two on the basis of morphological discontinuities as was the seventh group (F).which contained a collection of lupines with doubtful affinities (chemical or morphological). Overall, it is concluded that flavonoids are good specific characters in Lupinus. Their distribution, interspecifically, lends support to the recognition of some previously described subgeneric groupings that were based on morphology. In other cases, flavonoid data suggests affinities between some taxa that hitherto were considered unrelated.

Text

2010-03-29

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http://hdl.handle.net/2429/22895

Botany

University of British Columbia

Graduate