The Endemic Genera of the Fijian Islands.
The interest that is associated with the endemic genera of Hawaii fails to attach itself to those of Fiji. For this there are several reasons. In the first place, our acquaintance with the Fijian flora is much less complete. In the next place, the group holds a much less isolated position, and the history of an endemic genus may have a significance quite different from that connected with it in Hawaii. Fiji also lacks, on account of its submergence in the Tertiary period, those highly interesting genera of the Compositæ and Lobeliaceæ that form the chief feature in the early history of the flowering plants of Hawaii. Then, again, on account of our imperfect knowledge of the floras of the neighbouring groups of continental islands to the westward, the New Hebrides, Santa Cruz, and Solomon Groups, we can never feel quite confident that any particular genus is really peculiar to the Fijian archipelago. This is well brought out in the later history of the genera designated by Dr. Seemann in his Flora Vitiensis as peculiar to Fiji.
Of the sixteen genera enumerated by Dr. Seemann, and given in the table below, only about half now retain their character of being restricted to Fiji. Nor does it seem likely that future investigations will increase this number, since, judging from a remark made by Mr. Hemsley in his paper on the botany of the Tongan Group, explorations subsequent to those of Dr. Seemann, more especially those of Mr. Horne, have not apparently added a single new endemic genus to the Fijian flora. It will be seen from the list that at least four of the sixteen genera have since been found in the Malayan region, and in one case (Smythea pacifica) the same species occurs in both regions; whilst a fifth genus (Haplopetalon) has been recorded from New Caledonia.
There are, however, some peculiarities about the Fijian endemic genera that will attract our attention from the standpoint of dispersal. One remarkable feature is the paucity of species. Almost all the genera are monotypic, that is to say, they are only known by a single species. Amongst the twenty-eight Hawaiian genera that are strictly endemic, only four or five are monotypic, and they are mostly regarded by Hillebrand as worn-out, decadent types found in only one or two islands. In Hawaii there are on the average six species to each endemic genus; and it is thus apparent that in the display of formative energy Nature has worked on very different lines in these two groups. Since the nine Fijian endemic genera belong to nearly as many different orders, the composition of this endemic generic flora is by no means homogeneous. It is, I venture to think, such a motley collection as one might expect in a region that has been exposed to wave after wave of migration from the west, with no lofty mountains, as in Hawaii, to afford a refuge against extinction. It by no means follows that all these endemic genera have been produced in Fiji. Some of them may represent genera that have become extinct in the large continental groups to the westward.
SEEMANN’S SIXTEEN FIJIAN ENDEMIC GENERA.
| Genus. | Order. | Number of species. | Character. | Fruit. | Affinities or other localities. |
|---|---|---|---|---|---|
| Richella | Anonaceæ. | 1 | Tree. | Baccate(?). | Indian in type (C). |
| Trimenia | Ternstrœmiaceæ. | 1 | Tree. | Unknown. | |
| Pimia | Sterculiaceæ. | 1 | Tree. | Small spinose capsule. | Related to Australian genera (S). |
| Græffea | Tiliaceæ. | 1 | Tree. | Unknown. | Near Trichospermum, a Fijian and Malayan genus (S). |
| Thacombauia | Humiriaceæ. | 1 | Shrub. | Drupe. | Order mainly South American. |
| Amarouria | Simarubeæ. | 1 | Tree. | Dry drupe. | Near Soulamea, a Malayan genus (S). |
| *Smythea | Rhamneæ. | 1 | Straggling shrub. | Capsule. | Also in Burma, New Guinea, and Malaya (IK), (Sc). |
| *Oncocarpus | Anacardiaceæ. | 2(H) | Tree. | Drupe. | Also in New Guinea (IK). |
| *Haplopetalon | Rhizophoreæ. | 2 | Shrub. | Unknown. | Also in New Caledonia (IK). |
| *Nesopanax | Plerandreæ. | 1 | Tree. | Drupe. | =Plerandra (IK). |
| Bakeria | Plerandreæ. | 1 | Tree. | Drupe. | |
| Pelagodendron | Rubiaceæ. | 1 | Shrub. | Berry. | |
| *Paphia | Ericaceæ. | 1 | Shrub. | Berry. | =Agapetes, a Malayan genus (IK). |
| *Carruthersia | Apocyneæ. | 2(H) | Climber. | Berry. | Also in Philippines (IK). |
| *Couthovia | Loganiaceæ. | 2 | Tree. | Drupe. | Also in Kaiser Wilhelmsland, New Guinea (So). |
| Canthiopsis | Loganiaceæ. | 1 | Shrub. | Drupe. |
Those genera marked * have since been found outside the group.
The authorities are thus indicated: (C)=Drake del Castillo; (H)=Horne; (IK)=Index Kewensis (S)=Seemann; (Sc)=Schimper; (So)=Solereder in Engler’s Nat. Pflanz. Fam.
The fact that several of them are fitted for dispersal by frugivorous birds is very suggestive of the lack of means of transport in later times. In the instance of Couthovia corynocarpa the drupes are known to be the food of fruit-pigeons at the present time (Seemann), whilst this is also true of Oncocarpus vitiensis, though this genus has since been found in New Guinea. Since, as will be pointed out in a later chapter, birds must still be fairly active in carrying seeds to Fiji from regions westward, it would seem that genera only become peculiar to Fiji when they fail at their source, and it is indeed doubtful whether any of the Fijian peculiar genera are home productions. One may instance in this connection the genus Pimia, the fruits of which are especially well suited for attachment to a bird’s plumage, yet it is only known from Fiji.
It should be here observed that no peculiar generic types have been recorded from the adjacent Tongan Group, and scarcely any from Samoa. Except perhaps with the Palmaceæ, no peculiar genera seem to be mentioned in Dr. Reinecke’s memoir on Samoa.
Summary.
(1) The Lobeliaceæ, like the Compositæ, take a prominent place in the early Pacific flora, being represented, more particularly in Hawaii but also in the East Polynesian or Tahitian region, by endemic genera of tall shrubby and tree-like species.
(2) Tree-Lobelias occur in other parts of the world, as in South America and tropical Africa; but it is especially on the higher slopes of the mountains of Equatorial Africa that they attain a development comparable with that of Hawaii.
(3) In Hawaii the Tree-Lobelias are most characteristic of the middle forest-zone (3,000-6,000 feet), where the temperature is mild, the rainfall heavy, and the atmosphere laden with humidity.
(4) The affinities of these endemic genera of the Lobeliaceæ are mainly American; but their generic distinctions have been both exaggerated and disguised by redundant growth.
(5) From the distribution of the genera and species within the Hawaiian Group it is evident that, as with the early Compositæ, the original Lobeliaceous immigrants were not all contemporaneous arrivals. Some of the genera are on the point of extinction, whilst others are in their prime.
(6) The absence of the Lobeliaceæ from the groups of the Fijian area (Fiji, Tonga, Samoa) is probably to be connected, as in the case of the absence of the early Compositæ, with the circumstance that the general distribution of these two orders over the tropical Pacific occurred during the Tertiary submergence of these archipelagoes.
(7) These endemic genera of the Lobeliaceæ possess the same facilities for dispersal that are owned by other genera with minute seeds, such as Cyrtandra, &c., that are dispersed over the Pacific; but in the case of the Lobeliaceæ the agencies of dispersal have been for ages suspended.
(8) This suspension is to be associated with the diverting of the main stream of migration from its source in America, during the early age of the Lobeliaceæ and Compositæ, to a source on the Asiatic side of the Pacific.
(9) The Hawaiian endemic genera other than those of the Compositæ and Lobeliaceæ arrange themselves in two groups—an earlier group containing highly differentiated Caryophyllaceæ and Labiatæ, and belonging to the age of the Compositæ and Lobeliaceæ; and a later group, characterised by Rubiaceæ and Araliaceæ, which marks the close of the first era, as well as the change in the main source of the plants from America to the Old World, the beginning of the Hawaiian forests, the appearance of the Rubiaceous drupe, and the first active intervention of frugivorous birds.
(10) Though there are no “difficult” or “impossible” fruits (fruits, the dispersal of which is not easy to explain) amongst the forty and odd endemic genera of Hawaii and Tahiti, it is noteworthy that in some cases the fruits are seemingly little fitted for dispersal now, and that this deterioration in capacity for dispersal is to be frequently associated with more or less failure of the inter-island dispersal in the case of Hawaii.
(11) The interest associated with the Hawaiian endemic genera fails to attach itself to those of Fiji, where genera only seem to have become peculiar because they have failed at their sources in the regions to the west. The endemic genera of the Compositæ and Lobeliaceæ are here lacking, and this is true also of the neighbouring Samoan and Tongan Groups, it being held that the age of the general dispersion of these orders over the Pacific corresponded with the Tertiary submergence of the archipelagoes of the Western Pacific. Those of Fiji, which do not amount to ten in number, belong to nearly as many orders and present a motley collection such as one might look for in a group much less isolated than Hawaii and exposed to wave after wave of migration from the west.
CHAPTER XXIII
THE ERA OF THE NON-ENDEMIC GENERA OF FLOWERING PLANTS
The Mountain-Floras of the Pacific Islands as illustrated by the Non-endemic Genera
The mountain-flora of Hawaii.—A third of it derived from high southern latitudes.—An American element.—Compared with Tahiti and Fiji.—Capacities for dispersal of the genera possessing only endemic species.—Acæna, Lagenophora, Plantago, Artemisia, Silene, Vaccinium, &c.—Capacities for dispersal of the genera possessing non-endemic species.—Cyathodes, Santalum, Carex, Rhynchospora.—Fragaria chilensis, Drosera longifolia, Nertera depressa, Luzula campestris.—Summary.