Ficus in the Solomon Islands and its bearing on the post-jurassic history of Melanesia

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Abstract
The fig-flora of the Solomon Islands (Bougainville to San Cristobal) is exceptionally rich (63 species, 23 endemic). It is related to that of New Guinea but differs in the species of four groups, namely subgen. Pharmacosycea (3 endemics), subgen. Ficus sect. Sycidium ser. Scabrae (6 endemics), sect. Sycocarpus subsect. Auriculisperma (5 endemics), and subsect. Sycocarpus (8 endemics); the other endemic is in sect. Adenosperma . The effect is a flora that defines the Solomons as a geographical unit. These four subgeneric groups appear to have arisen in this part of Melanesia and to have spread thence with varying success through Malaysia to the Asian mainland. Eastwards ser. Scabrae has evolved in Polynesia and subgen. Pharmacosycea in New Caledonia. Most of the 36 species common with New Guinea terminate their eastward distribution in San Cristobal; nine extend to New Hebrides and two of these to Polynesia. Four dispersal arcs are recognized: (i) the Melanesian Foreland linking northern New Guinea, New Ireland, New Britain, the Solomons, New Hebrides and, perhaps, Fiji; (ii) the Australian Foreland linking southern New Guinea, Queensland and New Caledonia; (iii) a subsidiary connexion between the Solomons, New Hebrides and New Caledonia; (iv) the tropical Pacific fig-route which, as the oldest, connected with tropical America. These conclusions put Melanesia as a centre of Ficus -evolution and, therefore, the distribution of the Melanesian groups of Ficus becomes a prime chronological factor in the post-Jurassic history of Melanesia. Ficus is taken as an example of the durian theory in the sense of the evolution of the modern tree. The rule is formulated that, without a pachycaul predecessor, there can have been no major subgeneric evolution. Surviving pachycauls are descendents of the stocks from which the new groups have spread. Hence pachycaul geography becomes a basis for phytogeography. New taxa are : F. cristobalensis, F. dissipata, F. illiberalis, F. immanis, F. macrothyrsa var. lancifolia, F. novae-georgiae, F. oleracea var. villosa, F. pseudowassa, F. scaposa and F. tanypoda .

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