The Geography of Phytochemical Races

272 6 Oceanic Islands
A single population of Peperomia exists on Inaccessible Island, which lies
approximately 40 km to the southwest of Tristan at 37°19′S,12°44′W (Preece et al.,
1986). Examination of the specimens revealed that the Inaccessible material bore
striking resemblance to P. berteroana, one of the Juan Fernandez endemics, and
that the similarity between the two should be recognized by defi ning the Inaccessible
specimens as P. berteroana Miq. subsp. tristanensis (Christoph.) Valdebenito
(Valdebenito et al., 1990b).
Part of the examination of Juan Fernandez endemic species had involved an analysis
of the fl avonoid profi les of specimens of Peperomia from both islands. Recall
that the profi les of P. berteroana from Masafuera and Masatierra were different
from each other. With these data on hand, it was simple to compare those profi les
with the pigment profi le of Peperomia from Inaccessible Island. The fi nding that
the Inaccessible profi le matches exactly that of plants from Masafuera not only
provides additional support for a close relationship between the subspecies, but also
suggests that propagules that gave rise to the Inaccessible population originated
from Masafuera. Flavonoid data for this disjunct set are presented in Table 6.4.
The connection between the Juan Fernandez Islands and the Tristan da Cunha
Islands represents the fi rst involving a Pacifi c Ocean-Atlantic Ocean disjunction.
Owing to the comparative richness of Peperomia populations on the Juan Fernandez
Islands, and the very limited population on Inaccessible Island, it seems entirely
appropriate to suggest that the propagule(s) originated on the former. Valdebenito
et al. (1990a) suggested that a possible agent for propagule delivery was the petrel,
a long-distance fl yer known to visit both island systems. Additional material of
the Inaccessible Island population has been collected for future study of the taxon
(T. F. Stuessy, personal communication, September 2001).
6.4.6 Sophora (Fabaceae)
Sophora, a leguminous genus of perhaps 45 species (Mabberley, 1997, p. 671), offers
a number of very interesting distributional problems. Members of sect. Edwardsia
Taxon Flavonoidsa 1–7 8 9 10 11–14
P. b. subsp. berteroana (MT) b Table 6.4 Flavonoid profi les of Peperomia berteroana from the Juan Fernandez Islands and
Inaccessible Island (from Valdebenito et al., 1992b)
+ + + + −
P. b. subsp. berteroana (MF) + − − − +
P. b. subsp. tristanensis + − − − +
a Compounds 1–7: acacetin, acacetin sulfate, diosmetin 7-Glc, diosm etin
7-GlcRhm, luteolin 7-DiAra, and luteolin 7-sulfate; 8 = apigenin 7-Glc-sulfate;
9 = luteolin 7-GlcRhm; 10 = diosmetin 7-Glc; 11–14: acacetin 7-Glc-sulfate,
diosmetin C-GlcAra, diosmetin 7-GlcAra, and diosmetin 7-sulfate.
b MT = Masatierra; MF = Masafuera.