Preliminary plant-geographical analysis of the Pacific, as based on the distribution of Phanerogam genera

(1) The accompanying map illustrates the hierarchy of the floristic subdivision of the Malaysian-Pacific area and its demarcation against the New World flora. The way of linking it with the mainland of Eastern Asia has not been worked out. Further it has not been attempted to subdivide the Australian flora including Tasmania. The following names are proposed: (2) As has appeared from the surveys the number of endemic genera pro subdivision cannot be placed in any proportion to the surface of that subdivision; this appears for example from the following figures: (3) If two islands are comparable ecologically (latitude, altitude, climate, soils) and are at comparable distance from a continental flora or other big plant source, the island with the smallest surface has the largest percentage of world-wide genera (type 1). This appears from a comparison of Samoa (43%) with Tonga (50%), and Tonga with Cook I. (61.6%). (4) The highest percentage of worldwides is found in the coral islets and atolls. (5) For ecologically more or less comparable islands the rule seems to be that the distance to a continental flora or other rich plant source and the total number of genera are inversely proportional. For example Lord Howe I. (surface 13 sq.km) at a distance of 500 km from Australia has 126 genera and Norfolk I. (surface 40 sq.km) at a distance of 1600 km from Australia has only 103 genera, even though it is thrice as large as Lord Howe I. (6) Generic endemism and specific endemism often do not go parallel. The Galápagos, Marquesas, New Hebrides, and Rapa I. have a high specific endemism, but possess very few endemic genera. (7) a. In the Pacific the Malaysian influence reaches in general wide and far. b. The Australian influence in the Pacific is proportionally small and affects mostly the southern Pacific. c. The influence of the American flora is surprisingly small, even in islands which are situated relatively very close to the. New World if compared with their distance to the Old World, for example the Marquesas, Easter I., etc. d. If the South American element is found far in the Pacific it is almost restricted to the subantarctic part of it. (8) The method of the demarcation knots is only useful if islands or island groups are contrasted which have a comparably rich flora, containing a number of genera of about the same order, for example Formosa and the Philippines, Malaysia and Australia, the Solomons and the New Hebrides (the latter with respectively 431 and 371 genera: demarcation 60 %). If the areas are very dissimilar in number of genera the method of demarcation knots will result in a wrong picture of the situation. In the latter case the approach for the estimate should be made in another way, for example by focussing attention to the number of genera which occur in the poorest of the pair and not in the richest. An illustrative example of this is a comparison between New Caledonia and the Loyalty Islands, where the demarcation knot would be 61 % on account of the very high number of New Caledonian genera which do not occur in the Loyalties. Actually, only 2 genera occur in the Loyalties which have not been recorded from New Caledonia, showing that the Loyalty Islands flora is merely a depauperated New Caledonian one.