The Geography of Phytochemical Races

134 3 After the Ice
of these three taxa. An analysis of allozyme variation, as they suggested, or other
macromolecular approach, would certainly seem to be in order.
The remaining members of Arnica subgenus Arctica have been subjected to
fl avonoid analysis as well (Downie, 1988; Downie and Denford, 1988). Relevant to
the present discussion of glacial refugia are their observations on the distribution and
fl avonoid chemistry of the A. angustifolia Vahl complex. Reappraisal of morphological
data using multivariate analysis led Downie (1988) to realign previously recognized
subspecies into just two: (1) A. angustifolia subsp. angustifolia, which comprises
subspecies angustifolia, attenuata, sornborgeri, intermidia, iljinii, and alpina and
plantaginea (see Downie, 1988 for taxonomic details); and (2) A. angustifolia subsp.
tomentosa (J. Macoun) G. W. Dougl. & G. Ruyle-Dougl. Arnica angustifolia has much
in common with A. frigida Meyer ex Iljin in terms of its breeding biology, the existence
of several cytological races, and possession of a comparatively simple fl avonoid
profi le. Although the distribution of A. angustifolia subsp. angustifolia is essentially
continuous across North America—ranging from Alaska to the eastern Arctic and
Greenland—the combined evidence suggests that the present range has resulted from
reoccupation of these areas from refugia following retreat of the Wisconsin ice sheet.
Owing to the high level of apomixis within the taxon, few genera in Asteraceae
offer as much challenge in species defi nition as does Antennaria. Anderberg (1994)
summarized the situation well in describing the genus as consisting of “… ca. 70 to
several hundred species depending on species concept.” This situation is very well
represented in the North American fl ora by A. rosea E. Greene. Morphometric
analysis revealed that the main source of morphological variation in the complex
comes from six sexually reproducing progenitors. This situation has been reviewed
in depth by Bayer (1990, and citations therein). The bulk of Bayer’s work has been
directed at understanding the contributions of the various sexual species involved
in the establishment of each of the agamospermous species complexes. Of concern
to us in the present context is the pattern of distribution of the A. rosea complex in
North America. Antennaria rosea occurs over a very large area in western North
America ranging from southern California, Arizona and New Mexico north to the
Arctic and east to Hudson’s and James Bay. It also occurs disjunct in eastern Canada
and along the shores of Lake Superior. The northern half of its range is similar to the
range occupied by some of the members of Arnica discussed above. Bayer’s work
addressed questions of geography only as they pertained to ranges of occurrence
of the participants in the formation of the species complexes. Since correlations of
fl avonoid profi le complexity and ploidy level relative to the origins of present distribution
patterns provided interesting results in the Arnica complexes, it would seen
reasonable that studies of Antennaria might yield similarly interesting results.
3.1.4 Menziesia (Ericaceae)
Menziesia Smith, a genus of perhaps eight species, is one of many genera that exhibit
an eastern North American, western North American, eastern Asian distribution.