The Geography of Phytochemical Races

7.9 Perityle emoryi (Asteraceae) 295
borne out by the accumulation of 16 of the fl avonoid glycosides by the latter. The
remaining three species yielded only seven or eight glycosides each. A further
distinguishing feature was the observation that sulfated fl avonoids were detected
only in L. tridentata and L. divaricata. While affording additional data to support
the similarity of these two species, fl avonoid glycosides did not provide any further
insight into their evolutionary history.
Speculation on the age of L. tridentata in North America is based to some extent
on the lack of appropriate desert habitats until the end of the Wisconsin glaciation,
which has been reckoned to be about 11,000–12,000 years ago at lower elevations
and about 9000 years ago at higher elevations. Exploration of rat middens revealed
no material of Larrea older than about 11,000 years. It seems likely that propagules
of Larrea, most likely dispersed by birds, arriving at the time of the warming and
drying of the regions now occupied by deserts, found new habitats, became established,
and differentiated cytologically into the races that now exist.
7.8 Lasthenia (Asteraceae)
Lasthenia, a genus visited before in this review, is western North American in occurrence
except for L. kunthii (Lessing) Hook. & Arn. (the type species), which occurs
in Chile. Lasthenia kunthii bears strong morphological similarities to L. glaberrima
DC., one of the Californian species. The two species also have the same chromosome
number (n = 5) and form highly fertile hybrids in artifi cial crosses (Ornduff, 1963),
all of which led Ornduff (1966) to place them together in sect. Lasthenia. A survey
of fl avonoids of the genus (Bohm et al., 1974) revealed that the pigment profi les
of these two taxa were among the simplest of the genus lacking both anthochlors
(aurones and chalcones) that characterize sections Baeria and Burrielia, and the patuletin
(6-methoxyquercetin) derivatives seen in some members of sect. Ptilomeris
and in sect. Platycarpha. The compounds observed in L. kunthii and L. glaberrima
are based on quercetin, with quercetin 3-O-galactoside held in common. Lasthenia
glaberrima also exhibited the 3-O-glucuronide and a 3-O-rhamnosylgalactoside,
whereas L. kunthii afforded only one other compound, a 3-O-galactosylglucoside.
It is likely signifi cant that L. glaberrima is self-compatible, whereas most other
species of Lasthenia are self-incompatible. Long-distance dispersal of a single
propagule of L. glaberrima would then have been suffi cient to establish the species
in Chile. It is, of course, entirely possible that propagules from one or another of the
self-incompatible species could also have made the journey, but without a reproductively
compatible partner their fates were sealed.
7.9 Perityle emoryi (Asteraceae)
Perityle is a genus consisting of ca. 63 species distributed primarily in western North
America and Mexico, with one species in Chile and Peru (Karis and Ryding, 1994).
The species of interest is P. emoryi Torr., an annual, polyploid, weedy species that