The Geography of Phytochemical Races

274 6 Oceanic Islands
Fig. 6.11 Map showing location of Lord Howe Island
McDougall et al. (1981), who reckon it to be approximately 6 million years old. One
of the taxa endemic to the island, Carmichaelia exsul F. Muell., has been included
in at least two studies of this genus. Carmichaelia (Fabaceae, Papilionoideae) consists
of perhaps as many as 40 species, of which all but C. exsul are endemic to
New Zealand. In his study of the fl avonoids of the genus, Purdie (1984) pointed out
that species often exhibit a good deal of morphological variation, leading in many
cases to unclear taxonomic limits. It was his intent to assess the usefulness of fl avonoids
as an additional source of characters. His study involved 31 species of Carmichaelia
and included the Lord Howe Island endemic. He reported that the profi le of
the genus consists of two C-glycosylfl avones, which were not further identifi ed, a
series of fl avonol 3-O-, 7-O-, and 3,7-di-O-glycosides, and ubiquitous isofl avones.
The fl avonol aglycones were identifi ed as kaempferol, quercetin, and isorhamnetin.
Kaempferol and quercetin derivatives were observed in all taxa, whereas isorhamnetin
was missing from two. Flavonol 3-O-glycosides were observed in all taxa; all
other compounds showed distinct patterns in their occurrence. Of particular interest
was the fl avonoid profi le of C. exsul, which consisted only of kaempferol and
quercetin 3-O-glycosides and isofl avones, and was the simplest pattern observed
in this study. The only other taxon that lacked isorhamnetin was C. kirkii Hook.
f., which occurs in the east central part of the South Island (vicinity of Canterbury
and Otago). Carmichaelia kirkii, the sole member of subgen. Kirkiella (as used by
Purdie) is also distinguished from all other species in possessing an unidentifi ed
aglycone. The species is also unique within the genus in being a liana. The absence
of isorhamnetin from both C. exsul and C. kirkii would appear to have no signifi -
cance. Members of other subgenera also lack certain fl avonoids in common with
C. exsul, but the signifi cance of the common absences and the reduced fl avonoid
profi le in the C. exsul cannot be determined without a better understanding of relationships
within the genus as a whole.