atoll research bulletin no. 392 the flora of - Smithsonian Institution ...

Nature of Exotic Species
Exotic species, which constitute 88 per cent (434 out of a total of 493 reported
species) of the flora of Nauru, dominate ruderal, houseyard and urban vegetation. Exotic
species include a wide range of ornamentals, weedy species, food plants and a number of
other useful species.
Ornamentals, which are normally confined to houseyard and village gardens,
comprise some 59 per cent (257) of the 434 exotic species. On Nauru, introductions by
travellers from Australia, Fiji and other areas with highly developed ornamental gar-
dening traditions; the absence of quarantine restrictions; and the almost total breakdown
in the subsistence economy, seem to be the main reasons for the disproportionate
importance of ornamental plants. Some of these ornamental, of course, have other uses
such as living fencing or for the preparation of medicines or garlands.
The proportions of the exotic flora composed of weedy species is 18 per cent (80
of 434 species), an indication of both the poverty of the competitive indigenous flora and
the highly disturbed nature of the vegetation.
Although food plants represent 16 per cent of the exotic flora, due to the harsh
environment, limited land area and limited focus on food production in Nauru, many of
these species are restricted in numbers or utility and are often represented by experimen-
tal attempts to diversify food production or by individual, often immature specimens of a
given species. Exotic food plants of particular importance on Nauru include numerous
edible pandanus cultivars (Pandanus tectorius), some of which are undoubtedly aboriginal
introductions, and the coconut (Cocos nucifera), also an aboriginal introduction. Recent
introductions of more localized importance, or of particular importance to contract
worker communities on Nauru include: the vegetables, hibiscus spinach (Hibiscus
manihot) , Chinese cabbage cultivars (Brassica spp.) , long beans (Vigna sesquipedalis) ,
amaranthus spinach (Amaranthus spp.) and pumpkin (Cucurbita pepo); the staple root
crops, taro (Colocasia esculenta) , tannia (Xanthosoma sagittifolium) , sweet potato
(Ipomoea batatas) and cassava (Manihot esculenta); a range of banana and plantain
cultivars (Musa cultivars); and the tree crops, lime (Citrus aurantifolia), guava (Psidium
guajava), mango (Mangifera indica), soursop (Annona muricata) and the horseradish or
drumstick tree (Moringa oleifem), all of which seem to do well in Nauru's harsh
environment. Important emergency or pig foods include Polynesian arrowroot (Tacca
leontopetaloides) and purslane (Portulaca spp.), both of which are found as naturalised
plants in the coastal vegetation of in ruderal sites.
Other useful exotic species include kapok (Ceiba pentandra), cotton (Gossypium
barbadense), tobacco (Nicotiana tabacum), and bamboo (Bambusa vulgaris), which were
all reportedly more abundant in thepast. As suggest&-avove, somelarger ~~eed~xotics,
such as Adenanthera pavonina, Annona spp., Casuarina equisetifolia, Lantana camara,
Leucaena leucocephala, Mangifera indica, Muntingia calabura and Psidium guajava,
some which are classified as ornamentals, food plants or other useful plants, have