Floristic relationships between New Caledonia and the Solomon Islands

New Caledonia and the Solomon Islands are compared briefly as to location, size, climate, and other physical features. Possibly 585 seed-plant genera known from the Solomon-Santa Cruz groups are indigenous there, and 692 similarly may be indigenous in New Caledonia. Unknown from New Caledonia are 272 of the Solomons genera and unreported from the Solomons are 379 of the New Caledonian genera. Thus only 313 genera, or 32-5 %, of the 964 total genera are common to both archipelagoes. It is suggested that the relatively smaller generic flora of the Solomons reflects the more limited botanical exploration of the Solomons as well as the greater variability of climate, substrate, and vegetation types of New Caledonia. Also New Caledonia is believed to have a much older, more relict flora than the Solomons, as indicated by the numerous conifers and primitive angiosperms (four genera of which are primitively vesselless). The far greater generic endemism (perhaps 94 genera or 13-5%) of New Caledonia as compared with the Solomons (5 genera or 0-86%) is explained by the much greater isolation in space and time of New Caledonia from other land masses. New Caledonia has its closest botanical relationships with coastal Queensland and New Guinea, with which it shares 474 and 482 genera respectively. Its floristic affinities are less with New Zealand and the Outer Melanesian Arc. The Solomons, on the other hand, have their closest botanical ties with New Guinea through New Britain and New Ireland. At least 572, or almost 98%, of the 585 genera recorded from the Solomons are represented also in New Guinea. As with the fauna, however, the Solomons flora is much attenuated, lacking many of the characteristic New Guinea genera, especially those of the montane and alpine regions. The break between the Solomon Islands and the Santa Cruz Islands is much greater than that between New Guinea and the Bismarcks and between the Bismarcks and the Solomons.