Juan Fernandez Islands

Miller (1989) is the question of how such an ancient organism has come to exist on a comparatively new oceanic island. Long-distance dispersal is an unlikely explanation for the present situation. Dispersal over shorter distances from island to island seems a reasonable possibility, with subsequent disappearance of many, or apparently all in the present case, of the intermediate stepping stones. Invocation of island hopping, after all, has many precedents. As Miller (1989) pointed out, obviously some vascular plant lineages have survived, some of which may have histories that reach back to the Antarctic flora. Needless to say, deep phylogenetic analyses would be helpful in addressing this question. 

The Juan Fernandez Islands, Chile, he east of the South American mainland at approximately 33°30 S, 80°W (Fig. 6.8). The archipelago consists of two main islands, Masatierra, which lies about 660 km from the mainland, and Masafuera, which lies 150km further west. A third, small island, Santa Clara, lies off the western end of Masatierra and probably was attached to Masatierra at one time. The ages of the islands have been determined using potassium-argon dating methods to be 5.8 2.1 million years for Santa Clara 4.23 0.16 million years for Masatierra and 2.44 0.14 million years for Masafuera (Stuessy et ah, 1984). 

The vascular flora of the Juan Fernandez Islands consists of 361 species and includes 53 ferns, 65 monocots, and 243 dicots. There are 126 endemic species, 12 endemic genera, and one endemic family, Lactoridaceae (Stuessy et ak, 1992). A considerable amount of work has gone into attempts to establish evolutionary 

---

Fig. 6.8 Map of the Juan Fernandez Islands (Mt=Masatierra, Mf=Masafuera), Tristan da Cunha (T.d.C.), and Inaccessible Island in relation to South America. The location of the Falkland Islands (Islas Malvinas) is included...

Table 6.3 Flavonol glycoside profiles of Juan Fernandez Islands species of Gunnera compared to species from South America and Mexico (from Pacheco et al., 1993)...

Table 6.4 Flavonoid profiles of Peperomia berteroana from the Juan Fernandez Islands and Inaccessible Island (from Valdebenito et al., 1992b)...

DNA rerstriction site mutations and the radiation of Robinsonia (Asteraceae Senecioneae) on the Juan Fernandez Islands. Plant Syst. Evol. 184 233-239. 

Pacheco, P., Crawford, D. J. and Stuessy, T. F. 1991b. Natural interspecific hybridization in Gunnera (Gunneraceae) of the Juan Fernandez Islands, Chile. Pac. Sci. 45 389-399. 

Gunneraceae) in the Juan Fernandez Islands, Chile. Guyana Botanica 50 17-30. 

Dendroseris and Robinsonia, tree Compositae of the Juan Fernandez Islands. Opera Bot. 92 195-215. 

Stuessy, T. F., Foland, K. A., Sutter, J. F., Sanders, R. W. and Silva, O. M. 1984. Botanical and geological significance of potassium-argon dates from the Juan Fernandez Islands. Science 225 49-51. 

---