The Geography of Phytochemical Races

208 4 Intercontinental Disjunctions
4.4.6 Nothofagus (Nothofagaceae)
If one were to select a single example from the plant geography literature
that best encapsulates the history of the subject, one would be hard pressed to
fi nd a better one than the story of the southern beeches. In fact, van Steenis
(1971, 1972) begins the title of his paper with the words, “Nothofagus, key genus
in plant geography . . ..” Nothofagus consists of 35 species found in temperate
South America ( Argentina and Chile), New Zealand, Australia (including
Tasmania), New Guinea, and New Caledonia. Writing in the introduction to his
recent work on the molecular systematics of the genus, Paul Manos (1997) noted
that explanations for this disjunct distribution have varied over the years and
have depended to a large extent upon the current theory of the Earth, that is,
whether continents were fi xed (the stabilist perspective), or whether they moved
(the mobilist perspective).
This is not the place for a detailed discussion of the evolutionary history
of Nothofagus. Entry into the older literature can be found in papers describing
studies of morphological information (Hill and Jordan, 1993), isozyme data
(Haase, 1992), and DNA sequences (Martin and Dowd, 1993; Linder and Crisp,
1995; Manos, 1997; Setoguchi et al., 1997). Important insights into problems of
Nothofagus biogeography, based upon a variety of data sources, have been discussed
by Swenson and Hill (2001) and Swenson et al. (2001a, b).
Pollen has played a major role in understanding the history of and relationships
within Nothofagus. An extensive study of pollen revealed eight types, four
of which characterize extant species (Dettman et al., 1990). Analysis of the various
data sets from the abode studies resulted in the emergence of four groups,
each of which was characterized by one of the pollen types. This is in agreement
with the most recent taxonomic treatment of the genus in which each of the fours
groups is considered as a subgenus (Hill and Read, 1991). The occurrence of these
types is as follows: subgen. Nothofagus, characterized by pollen type “fusca A”
occurs in South America; subgen. Fuscospora, with pollen type “fusca B,” occurs
in South America, New Zealand, and Tasmania; subgen. Lophozonia, with pollen
type “menziesii”, occurs in South America, New Zealand, and Australia (including
Tasmania); and subgen. Brassospora, with pollen type “brassii”, consists of species
restricted to New Guinea and New Caledonia.
The only secondary chemical data available for Nothofagus that relates to the
geographic distribution of any of the species is a study of exudate fl avonoids
of four species of subgen. Fuscospora (Wollenweber et al., 2003). Structures
were determined for compounds isolated from: N. alessandri Espin., N. fusca
(Hook.) Oerst., N. gunnii (Hook.) Oerst., and N. solandri (Hook.) Oerst. Nothofagus
alessandri is a Chilean species, N. gunnii occurs on Tasmania, and N.
fusca and N. solandri are New Zealand species. The compounds identifi ed are
the fl avonol galangin (3,5,7-trihydroxyfl avone) [365] (see Fig. 4.15 for structures
365–371) and its 3- and 7-monomethyl ethers, 8-hydroxygalangin [366]
and its 3- and 8-monomethyl, 3,7- and 7,8-dimethyl, and 3,7,8-trimethylethers,