On S. Tomé and Príncipe, the predominant climax vegetation is of the humid tropical type, evergreen and heterogeneous. According to some histórical data on the islands, the arrival of the Portuguese transformed the natural environments of the archipelago; forests were cut down to make way for large plantations and exotic species were introduced. These were mostly food species and pets. One might say nearly all animal and plant species on the islands were, after a fashion, introduced.
As table 7 illustrates, 297 species now grown were introduced by man. There are distributed trhoughout 87 families. The fabaceae, solanaceae, poaceae, malvaceae and myrtaceae are the most abundant.
Moraceae, namely Artocarpus heterophyllus (jaqueira), Artocarpus comunis (fruteira), Treculia africana (izaquenteiro) and Musaceae, Musa sppl. (banana-tree) are noteworthy for their fruit, which constitute staples of the Santomean diet. In fact these species have become easily naturalized as they are capable of wide dissemination. They range from sea level to high altitudes.
Given current knowledge of the country’s flora, a total of 1260 plant species exist in the archipelago, of which 933 are indigenous, 297 are cultivated and 148 are endemic (see table 1 below). 14 are new to science and included in the group orchidaceae (see table 6 below).
Of the 1260 species, 105 are angiosperms, with 103 dicotyledons and 2 monocotyledons.
Among angiosperms a few are relevant to pasture and foraging, mostly the poaceae and leguminous plants.
The flora of the Santomean archipelago also includes a group of non-vascular plants, the bryophytes, which are represented by circa 22,000 species in the world. Humid regions see an abundance of the genera Marchantia, Anthoceros and Polytrichium.
Marchantia grows close to the ground while Campylopus and Polytrichium, which appear to be the most common genera, cover rocks, logs and gulleys.
The works undertaken in São Tomé and Príncipe by national and foreign botanists on several field missions, whose data have been published, show that pteridophytes are a rather old plant group from the evolutionary point of view. In fact, ferns appeared after bryophytes.
In the Santomean archipelago, pteridophytes contribute 13 endemic species as shown in the table 2, below. (Source: Pteridophytes of São Tomé and Príncipe) They are distributed throughout 28 different families: Aspleniaceae, 24 species; aspidiaceae, 15 species; Hymenophyllaceae, 12 species; Polypodiaceae and Pteridaceae, 10 species; Thelypteridaceae, 9 species; Selaginellaceae, 8 species and Nephrolepidaceae, 6 species. Other families present a relatively low number of specific diversity. Especially noteworthy is the Cyatheaceae family, which presents arboreal species that can grow to 3 meters in height. For this reason they are known as giant ferns, a rarity in the plant world.1
Fungi and mushrooms
The first report on biodiversity does not estimate the number of fungi and mushrooms existing on our islands, perhaps due to lack of research into this topic.
According to data published by the magazine “Actividade Rural” (“Rural Activity”), published by ADRA, an NGO, for the agrarian sector, farmers have run into problems with disease control and blights from these fungi:
Collectrichum coffeanum, which causes rhizoctoniosis, a disease affecting coffee plants
Colletotrichum lindemuthianum, causing anthracnosis, affecting beanstalks
Corn carbuncle (fungus) affecting corn (Zea maïs)
Uromyces apendicolatus, affecting beanstalks.
At the moment, knowledge on fungi present in the country is limited and further research is necessary.
Where mushrooms are concerned, Santomean mycology possesses great diversity. Mushrooms would seem to exist mostly in humid, shaded areas. The species found are from the genera Lentinus and Termitomyces, the latter including white mushrooms, which are abundant. Finally there is the genus Cantharellus, represented by several colored species. These genera probably belong to the group Basidiomicetes.
Lichens (symbiotic association of algae and fungi)
Lichens are symbiotic associations of algae, the photobiont, and fungi, the mycobiont. The genus Usnea grows in long strands, hanging from tree branches; widely distributed from sea level to mountaintops, where trees would seem bearded, given the profusion of said lichens. They provide accurate indicators of environmental conditions. Therefore, it would be urgent to carry out more research to inventory and describe these lichens. Only thus can we contribute towards their preservation.
2.7.12 Agro-ecological units and plant communities
According to Lains e Silva's work on the Agricultural Aptitude Chart of São Tomé and Príncipe, the country is divided into six agricultural areas. There are zones for cocoa, coffee, rubber, tea, oil palm and coconuts.
The plant communities of note are the following:
Aquatic and semi-aquatic herbaceous associations dominated by Struchium sparganophora (Libô d’água), Rorippa nastrutium (Leaf agrião), Pisticcia stratiotes (Alface d’água) and Costus afer (Uncoetê).
Ruderal herbaceous associations represented by Panicum maximum, Boerhavia difusa Cynodon dactylon e Eragrostis superba, Euphorbia hirta, Achyrantes aspera and Celosia gonfrenoides; they grow on cultivated land, near houses.
Post-cultivation, colonizing herbaceous associations constituted by Panicum maximum, Cleome ciliata, Pteriduim aquilinum, Ageratum conyzoides and Panicum hochstetteri. They’re found in plantations of Manihot esculenta (tapioca), Xanthosoma sagittifollium (Matabaleira), Ananas comosus (pineapple), Zea mays (corn) and Licopersicum esculentum (tomato).
Associations of vascular epiphytes constituted by Nephrolepis biserrata as well as strangling and/or hemiparasitic plants such as: Cuscuta campestris, Ficus clamydocarpa and Schefelera manii.
Associations of coastal halophyles with typical species such as Ipomoea pes capre, Altenanthera litoralis, Hydrocotylle bonariensis and Blutaporum vermicular.